DCX2496 questions

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  • Saurav
    Super Senior Member
    • Dec 2004
    • 1166

    DCX2496 questions

    I've been reading many threads across many forums, and I thought I'd try to get a high-level picture of this thing, and whether my general conclusions are correct...

    * Sound quality - reports range from pretty good to awful. I suspect individual pickiness and/or biases against digital XOs plays a role here. For the people on this forum who've used one - what's your opinion? Both stock and/or modified?

    * Mods - is there a reasonably comprehensive list of what's available? I've found 2 or 3 vendors so far, as well as some roll-your-own instructions. I'm sure there's more.

    * Is it generally agreed that the analog output (and input, if you're using it) stage(s) are the first things to tackle when modding, and doing that will make significant improvements to sound quality, as well as level-matching for home hi-fi?
  • mazurek
    Senior Member
    • Mar 2006
    • 204

    #2
    Just use the digital input, sound quality is fine. Analog input is not as clean. It helps to have average sensitivity drivers when you place the volume control before the active crossover, high sensitivity drivers will have a more challenging noise floor.

    As with many things, I think a well integrated system is perhaps more important than absolute perfection of one component. Spending your time learning how to properly implement a well thought out transfer function in the DCX (rather than arbitary parametric eqs) will get you more mileage in my opinion. Also, you can implement your transfer function with a Marchand kit once you've settled.

    Comment

    • Saurav
      Super Senior Member
      • Dec 2004
      • 1166

      #3
      I have a turntable, so I'd be using the analog input at least for that source. Good point on the noise floor issue. I have high sensitivity drivers for the most part, but also low gain tube amps, so I don't know how much those would cancel each other out.

      I'm mostly looking at this for the flexibility, since I've struggled with designing analog (active and passive) crossovers for my dipole speakers. Like you say, if nothing else, this would be a good prototyping tool.

      Comment

      • sqkev
        Junior Member
        • Jul 2006
        • 6

        #4
        The analog input is horrible imo, way too much noise floor. Digital input is dead silent, I can't hear a thing having ears up close on the tweeters. Tons of flexibility as it's been known. You might end up not going back to passive at all, ever.

        Comment

        • CraigJ
          Senior Member
          • Feb 2006
          • 518

          #5
          Surav,

          If the dcx is good enough for Victor and AJ, it's good enough for me. All my dipole speakers wouldn't have been possible without the DCX. I've run ribbons to compression tweeters, and my two systems have been silent. The only hiss I've heard was from a prior Spectron Musician II amp.

          Give it a try, pretty affordable used.

          Cj

          Comment

          • jliedeka
            Member
            • Nov 2008
            • 30

            #6
            I would expect the balanced inputs of the DCX to reject noise. Did you try using a direct box on the analog or just RCA to XLR cables?

            I'm considering active speakers some time in the future and would probably go with the DCX. I was thinking of using a Samson S-Convert on the analog side but I guess I could try to find an ADC box.

            Jim

            Comment

            • mazurek
              Senior Member
              • Mar 2006
              • 204

              #7
              Originally posted by jliedeka
              I would expect the balanced inputs of the DCX to reject noise. Did you try using a direct box on the analog or just RCA to XLR cables?

              I'm considering active speakers some time in the future and would probably go with the DCX. I was thinking of using a Samson S-Convert on the analog side but I guess I could try to find an ADC box.

              Jim
              The noise on analog inputs is not just due to CMRR (common mode rejection ratio) issues. I used it with balanced cables from balanced outs on my soundcard. You can play some gain games to improve the noise performance on the analog inputs a little, but the digital inputs are best (and its d->a is just fine in my experience). Either is livable, you just have to turn off that critic inside of you and enjoy the music.

              I'm not saying these are necessary, but a while ago, I evaluated a couple pro<->consumer solutions (for a different application than the DCX). Transformers are great if you have hum problems, but you've got to pay for a good one. I measured a Rane Balance Buddy 22 and it had obvious high frequency attenuation. I then got a Jensen transformer, which measured pretty flat. All transformers will have low frequency harmonic distortion, but the Jensen is not so bad. Custom passive adapter cables often work just fine, if you have hum, unplugging your cable box is most often the solution. Measure any active converter you use (or transformer for that matter), you can't count on a device to be perfectly flat in frequency response.

              Comment

              • Saurav
                Super Senior Member
                • Dec 2004
                • 1166

                #8
                Originally posted by CraigJ
                If the dcx is good enough for Victor and AJ, it's good enough for me.
                I think I saw some posts from Victor where he said his DCX was modified. Don't know about AJ. How about yours?

                Comment

                • DancesWithBeers
                  Member
                  • Dec 2008
                  • 67

                  #9
                  Originally posted by Saurav
                  I've been reading many threads across many forums, and I thought I'd try to get a high-level picture of this thing, and whether my general conclusions are correct...

                  * Sound quality - reports range from pretty good to awful. I suspect individual pickiness and/or biases against digital XOs plays a role here. For the people on this forum who've used one - what's your opinion? Both stock and/or modified?

                  * Mods - is there a reasonably comprehensive list of what's available? I've found 2 or 3 vendors so far, as well as some roll-your-own instructions. I'm sure there's more.

                  * Is it generally agreed that the analog output (and input, if you're using it) stage(s) are the first things to tackle when modding, and doing that will make significant improvements to sound quality, as well as level-matching for home hi-fi?
                  Saurav,

                  Is this strictly an audio setup, or will you eventually want to incorporate into a home theater?

                  -DWB

                  Comment

                  • Saurav
                    Super Senior Member
                    • Dec 2004
                    • 1166

                    #10
                    Just audio. My HT system is pretty basic, and not DIY.

                    Another question - what are my options for a 4/6 channel amp? I'm currently using an A500 for the woofers and a DIY tube amp for the mid/tweeter, and if I go this route, I'll want to go fully active, since the mid/tweeter XO gave me the most trouble.

                    Comment

                    • dwk
                      Senior Member
                      • Apr 2005
                      • 251

                      #11
                      One option for a multichannel amp that also solves the volume control problem is a decent HT receiver provided that it has an analog-domain volume control. I discovered by accident (an inebriated guest spilled water into the back of the receiver, frying the DSP board) that my Cambridge 540R V2 has this setup. Frying the DSP board basically turned it into a 6-channel integrated amp, with a bonus .1 sub line out as well.
                      I'm not sure of what other units might also be useful for this type of thing, but I'd imagine that the NAD gear would.

                      The 540R isn't an uber high-end piece, but it's pretty decent. Held up well against an old Tact RCS 2.0 into a Monarchy SM-70 when I compared them on my Sapphire XL's.

                      There is actually one available on the 'gon right now (not mine) for $300. You could do FAR worse than this IMHO.

                      Comment

                      • CraigJ
                        Senior Member
                        • Feb 2006
                        • 518

                        #12
                        Originally posted by Saurav
                        I think I saw some posts from Victor where he said his DCX was modified. Don't know about AJ. How about yours?
                        Saurav,

                        I believe Victor initially modified his dcx to get six channel volume control for his modified amps. Whether there's a sound quality difference is unknown to me. Perhaps a pm to V will assist you.

                        My dcx is not modified. IMHO, I have some other ways to improve sound quality, like room treatments, that I need to perform first before spending $600+ on a mod. Oh, and I can only solder with a big iron. YMMV

                        Regarding amps, an inexpensive way to get started is to use a good quality used 7.1 receiver. I believe Davey once mentioned a mid level Marantz 7.1 channel receiver. Just make sure the receiver has 6 separate speaker outputs.


                        Craig

                        Comment

                        • AJINFLA
                          Senior Member
                          • Mar 2005
                          • 680

                          #13
                          Originally posted by Saurav
                          I think I saw some posts from Victor where he said his DCX was modified. Don't know about AJ.
                          Nope, no "mods".
                          Have a MSB pre and 2 HK receivers (Class AB and D) with 8ch thru-put for volume and/or amplification.
                          Multiple units can be interconnected if you need more channels.

                          cheers,

                          AJ
                          Manufacturer

                          Comment

                          • sfdoddsy
                            Senior Member
                            • Sep 2000
                            • 496

                            #14
                            I've used various receiver options with my DCX as well as regular power amps. Depending on the power you need there are quite a few inexpensive 6 channel amps out there such as Rotel or Carver with gain knobs.

                            I now use an 8 channel pro-amp for fully balanced operation with good results (a QSC CX168) which I picked up for $600 on eBay. If you're on a tight budget, the Rane MA-6 would be a good choice. They usually go for under $200 used.
                            Steve's OB Journey

                            Comment

                            • Saurav
                              Super Senior Member
                              • Dec 2004
                              • 1166

                              #15
                              I was looking at some Rotel/Adcom/Carver amps on Audiogon. And someone pointed out Emotiva's new 5-channel amp which is also in that $500 price range.

                              I shouldn't have started thinking about this right before Christmas

                              Comment

                              • whoaru99
                                Senior Member
                                • Jul 2004
                                • 638

                                #16
                                Originally posted by jliedeka
                                I would expect the balanced inputs of the DCX to reject noise. Did you try using a direct box on the analog or just RCA to XLR cables?

                                I'm considering active speakers some time in the future and would probably go with the DCX. I was thinking of using a Samson S-Convert on the analog side but I guess I could try to find an ADC box.

                                Jim

                                Dunno about all of them, but some level converters really suck on the low end response...eg. ART Cleanbox in stock form.

                                IMO, level converters are seldom necessary unless one has some gain structure issues in their system.
                                There are some things which are impossible to know, but it is impossible to know which things these are. :scratchhead:

                                ----JAFFE'S PRECEPT

                                Comment

                                • CraigJ
                                  Senior Member
                                  • Feb 2006
                                  • 518

                                  #17
                                  Originally posted by Saurav
                                  And someone pointed out Emotiva's new 5-channel amp which is also in that $500 price range...I shouldn't have started thinking about this right before Christmas
                                  Sure you should, it's easier to justify. If looking at Emotiva, I'd suggest one more channel for a total of 6, and get the the UPA-7 http://emotiva.com/shop/cart.php?m=product_detail&p=32 for $599. I would also look into a used LPA-1, just my two cents. You're also going to need something for volume control. If you are going to use analog out, a quality stereo potentiometer after your turntable might be the ticket.

                                  Craig

                                  Comment

                                  • Saurav
                                    Super Senior Member
                                    • Dec 2004
                                    • 1166

                                    #18
                                    I have a pair of autoformers right now as a passive 'preamp'. But I see your point, I should send my ROKU to the digital input, no point using a DAC and then using the analog input for that. Ultimately I'll probably want to end up with a 6-channel volume control after the DCX, so the digital stage stays at full resolution.

                                    But all that's future I have a spare 5.1 receiver for now so I can use that as a 4-channel amp. I think I should get the DCX, get comfortable with it, see if I can figure out a way to work with those transfer functions in Speaker Workshop or if I'll need to spring for SoundEasy or something like that... the amp problem can wait for some time, I think. Getting the crossover right will probably have a bigger impact on sound than better amps or a modded DCX.

                                    Comment

                                    • A9X
                                      Senior Member
                                      • Jan 2007
                                      • 107

                                      #19
                                      Originally posted by Saurav
                                      I've been reading many threads across many forums, and I thought I'd try to get a high-level picture of this thing, and whether my general conclusions are correct...

                                      * Sound quality - reports range from pretty good to awful. I suspect individual pickiness and/or biases against digital XOs plays a role here. For the people on this forum who've used one - what's your opinion? Both stock and/or modified?

                                      * Mods - is there a reasonably comprehensive list of what's available? I've found 2 or 3 vendors so far, as well as some roll-your-own instructions. I'm sure there's more.
                                      I have 3 DCX, one modified and the others stock. The mod one has the analogue outputs bypassed and Lundahl transformers used it it's place on two of the outputs (4ch) for the biamped mains. The 5th and 6th channels of this unit will be for the subs later and I don't see the point in extra expense there.

                                      The other two DCX are for sides/rears and will stay stock for the forseeable future as I don't see the need to put the extra work into them.

                                      The mains are fed via an SRC digitally. This also is stock at the moment, but I have some analogue stages designed for the SRC and DCX i/p later. These are variants on some Pass designs.

                                      As is, they are excellent units, great xovers with the o/p stage modded. I can't see a need for anything more until I go to a DEQX later, once I've tried a borrowed unit hare beside the DCX and am convinced to spend the $.

                                      Gary Pimm's site is worth looking at for ideas on I/O mods.


                                      Originally posted by Saurav
                                      * Is it generally agreed that the analog output (and input, if you're using it) stage(s) are the first things to tackle when modding, and doing that will make significant improvements to sound quality, as well as level-matching for home hi-fi?
                                      Dunno if it's generally agreed, but I don't see the point in doing anything else until you get the analogue right.

                                      Comment

                                      • Saurav
                                        Super Senior Member
                                        • Dec 2004
                                        • 1166

                                        #20
                                        I've seen this SRC mentioned in a few places... so that plays the role of the ADC? Is it a better analog stage + ADC than what's in the DCX? Or do you only have digital sources, and the SRC is performing sample rate conversion, and no A-D?

                                        Comment

                                        • A9X
                                          Senior Member
                                          • Jan 2007
                                          • 107

                                          #21
                                          Originally posted by Saurav
                                          I've seen this SRC mentioned in a few places... so that plays the role of the ADC?
                                          Yes
                                          Originally posted by Saurav
                                          Is it a better analog stage + ADC than what's in the DCX?
                                          I believe it's identical to the DCX, but have yet to see a schematic to confirm this. If the assumption is correct, it will need to be changed out at some stage.
                                          Originally posted by Saurav
                                          Or do you only have digital sources, and the SRC is performing sample rate conversion, and no A-D?
                                          The SRC provides an easy multi digital input for a variety of inputs, upsamples them to 24/96 and feeds that to the DCX for the Mains. It was a $70 convenience item to allow me to connect the BRP (optical), server (coax) and some Pro ADCs I want to play with later via AES without having to unplug all the time.

                                          I also have a variety of analogue sources: TT's, R2R, VHS, Beta and cassette. The last three are rarely used, but come in handy for legacy items I come across, such as finding my old copy (VHS) of the late, great Joey Dunlop's IOM lap with an on bike camera.

                                          Comment

                                          • Saurav
                                            Super Senior Member
                                            • Dec 2004
                                            • 1166

                                            #22
                                            Thanks. I only have one analog and one digital source, so the DCX should be good enough for now.

                                            What's a workflow for crossover design with one of these units? I have measurements of my drivers on their current baffle. I can calculate the delays from the impulse responses and dial that in (and I believe the DCX can measure this as well). But after that, I'll need to combine DCX transfer functions with the driver responses. With Speaker Workshop, all I can think of is generating equivalent circuits in LTSpice, importing the FR curves, and combining them by hand with the driver curves... and I get no optimization functionality. Or I remove the phase delays in the measurements, give every driver a perfectly flat impedance, and try and come up with a passive XO in Speaker Workshop. Then I'd extract the filter transfer functions from there and try and generate an equivalent curve with the DCX. Both sound pretty laborious.

                                            I'm guessing something like LspCAD or SE would handle this a lot better? More stuff to spend money on

                                            Edit: I'd forgotten about LspCAD Lite. 3 drivers should be fine for me Anyone know if it can do active crossovers? I found the comparison page and it looks like it has all the optimizers of the standard version, but that doesn't explicitly mention active vs. passive crossovers. I couold send an email and ask...

                                            Comment

                                            • Saurav
                                              Super Senior Member
                                              • Dec 2004
                                              • 1166

                                              #23
                                              I just downloaded the LspCAD Lite 15-day trial to play with it. Unfortunately, the DCX2496 modeling seems to be missing from this version. I sent Ingemar a question about whether this was by design or not.

                                              Anyway, going through the manual, I see that the Lite version does not have the following features:

                                              Crossover emulator
                                              Snapshot
                                              Extra transfer function
                                              Voltage graph
                                              Current graph
                                              Polarplot
                                              Polarmap
                                              Power response
                                              KHF Tool
                                              Optimizer simplified

                                              Some of those I can do without. But I'm not so sure about the polar and power response calculators. That seems like something that I would want?

                                              Also, can LspCAD (the full version) handle dipole baffles in its power response / polar plot calculations?

                                              Comment

                                              • mazurek
                                                Senior Member
                                                • Mar 2006
                                                • 204

                                                #24
                                                You don't technically need LSPCad to set up your DCX, but I'm sure it could be helpful. I manually built up the transfer functions myself by decomposing them into shelfs, notches, etc. You can actually do this mathematically if your target function is of the right form, I wrote a short procedure for this in a previous post somewhere. It is important if you use this technique to measure the actual transfer function you are getting in case you made a mistake, or in some cases the required convention for parameters in the DCX is somewhat unclear.

                                                Comment

                                                • Saurav
                                                  Super Senior Member
                                                  • Dec 2004
                                                  • 1166

                                                  #25
                                                  You don't technically need LSPCad to set up your DCX, but I'm sure it could be helpful.
                                                  What I'd mostly like to use it for is the optimizer. I have an old demo of LspCAD standard lying around that I just played with (this one doesn't allow you to save a project). I set up the DCX transfer functions to roughly match the XO, shelves and notches that I have in my current analog filter. Then I let the optimizer run, and within a minute, I had much better phase matching between my drivers than anything I'd been able to achieve using Speaker Workshop.

                                                  SW has a very simple optimizer, which can only do one driver at a time, and only optimize to a given target curve. What I need is something that can handle multiple drivers, and optimize to 'flat with good phase tracking'. If there's a way to do that without using LspCAD/SE/CALSOD/whatever, I'd love to learn it.

                                                  Comment

                                                  • penngray
                                                    Senior Member
                                                    • Sep 2007
                                                    • 341

                                                    #26
                                                    Originally posted by sqkev
                                                    The analog input is horrible imo, way too much noise floor. Digital input is dead silent, I can't hear a thing having ears up close on the tweeters. Tons of flexibility as it's been known. You might end up not going back to passive at all, ever.

                                                    "horrible" is pretty subjective.

                                                    I have ribbon tweeters (Neopro5i) and I have horns (BMS4552) and I use the DCX with my two-way active designs in my Home Theater setup.

                                                    I use the Onkyo 885 (with balanced outputs) so I have no unbalanced to balanced issues.

                                                    I have put my ear up to all my tweeters listening to "noise" and I guess if the room is dead silent and there is no content I can hear something but two things should be considered.

                                                    1. No one should really be putting their ear up to their tweeter
                                                    2. There is no audible issues when content is being played back with SPL even over 60dB.

                                                    The DCX is an extremely flexible tool and it performs well beyond its cost!! THink about it, its below $300.

                                                    I have wanted to send one of my DCXs off to be modified by Micheal Mardis or Ric Schultz (Both do the mods) but I seem to always have another project on the go.

                                                    Other viable options is to maybe consider the Crown XTI amps, they have DSPs in them or the Hypex AS2.100 2-way plate amps with DSP but with the exchange rate being so bad I have decided to wait until later in 2010.

                                                    Comment

                                                    • penngray
                                                      Senior Member
                                                      • Sep 2007
                                                      • 341

                                                      #27
                                                      Saurav,

                                                      Have you read through DIY Audio's DCX thread?

                                                      for an XLR or TRS the signal is the DIFFERENCE between pin 2 and 3. Always. Pin1 is enclosure. Always. You can convert to unbalanced and all you have to remember is that the signal is between pin2 and pin3. At the unbalanced end you can connect pin3 to audio/signal ground. Do not connect pin3...

                                                      Comment

                                                      • Saurav
                                                        Super Senior Member
                                                        • Dec 2004
                                                        • 1166

                                                        #28
                                                        I've skimmed through it, but have I read every post in all 208 pages? No.

                                                        Though I hadn't checked that thread in a few days, and the recent posts about mod options are interesting. Thanks for pointing that out.

                                                        Comment

                                                        • penngray
                                                          Senior Member
                                                          • Sep 2007
                                                          • 341

                                                          #29
                                                          No problem, if you ever do a mod....I would love to read your conclusions.

                                                          I still hope to get one done in 2010.

                                                          Comment

                                                          • Victor
                                                            Senior Member
                                                            • Apr 2002
                                                            • 338

                                                            #30
                                                            I use 3 DCX2496 units in my set-up, - one runs the two front 3-way dipole speakers and the other runs the rear 2-way also dipole speakers. I do not see any sound quality issues with DCX, - it is quite transparent in stock form, if and when it works as it supposed to, which is not always the case. I had many issues with cracking sounds and shoot-through noise. I attribute those problems to the manufacturing quality control that Behringer must address. I also had noise coming out from the DCX outputs when the DEQ2496 was connected to the DCX2496 via AESBU balanced line.

                                                            Here is what I did to address those problems. My mods were done in order to take care of what I consider a less then adequate circuitry of the stock DCX. However, I must say that this is not a criticism of the DCX, because the original design criteria for the DCX were different then what we need in our HT.
                                                            I got rid of the output board all together and used a kit designed by J. Didden. It is a passive circuit. That definitely takes care of any cracking noises. I got it here


                                                            There is also an active kit (http://www.pilghamaudio.com/index.asp?pgid=51) that incorporates a remote volume control for all 6-channles and it works well, but I did not go that route due to its expense. In my view, passive output R-L-C circuit is the best here, because it requires no power, so no mods to the power supply are necessary, has the least distortion, and it offers a balanced output if you needed; - all for the very little money. Clearly the stock output board is inappropriate for the consumer applications. It has too high gain and uses topology and op-amps suitable for pro-audio, no Hi-Fi here, - we can do much better.

                                                            The shoot-through noise can be taken care by a more elaborate mod. The DCX has a ‘brain-dead’ digital input circuit. In really needs to go. There is a circuit board that works well, from the accounts that I know off, - here it is



                                                            The install is tricky, but doable for the experienced person. I think this mod is critical, because it fixes the most important problem of the DCX original design. I have yet to do this mod, but I will one day. There is another board that accomplishes the same from a French site.

                                                            Finally the change from AESBU input to SPDIF input must be done, but this is rather simple.

                                                            With above mods the DCX is perfect and it works well. One more thing, - the stock AKM D/A can also be replaced by a better chip, - AKM4396. I am doing this now and expect better performance in the end. It is a drop in replacement, but again it is a tricky thing due to the surface mount package. For this reason I will not do it myself but will ask somebody with a ‘surface mount’ experience to do it for me.

                                                            The biggest issue with the use of the DCX is volume control. I am using 2 motorised 4-gang Alps potentiometers with a remote control circuit. It works, but I am not happy. Better solution is a relay-driven attenuator, which can be multi-channel. The problem is that I need 12-channels! Another solution is a chip from TI or Analog Devices or Cirrus that will do the same. J. Didden implemented that kind of solution with his active mode, but it is only 6-channels and it is integrated inside the DCX, - no good for me, but might be fine for many. Anyway, I am still on the fence with volume control, as I have other projects in a pipe line.

                                                            By the way, it is questionable if dipole EQ can be accomplished with DCX2496 due to a possible high gain shelving filter requirement. I use it in my set-up, but I am not sure if this is a right thing to do. I need to do some measurements, but it sounds ok so far. It seems to me that for a dipole one might consider a kind of hybrid DCX-analog set-up, with the DCX doing all cross-over filtering and notches, while the analog board will do all shelving filters.

                                                            My concern has to do with a fact that whenever you ask the DCX to amplify the signal, you are running a risk of clipping, although a limiter available in the DCX might be helpful here. Anyway this is just a concern and I have no data to show that clipping is an issue. Perhaps someone can share the experience. Let me be more specific, - my dipole woofers (four 12-inch drivers in Linkwitz’s W-arrangement) need about 25 dB of boost at 20 Hz. I can do 15 dB with the DCX and it seems to work, but again I need to measure to be certain. So far I heard no clipping, but I am not driving them hard.

                                                            After I posted the above, I managed to do some transfer function simulations of the crossover that I need for my dipoles. Well, - clearly my DCX was not programmed right. Anyway, now I am quite sure that even the dipole woofers can be successfully accommodated with a DCX. There is a way to do this, but the stock output stage must be replaced for sure with a low gain (about 6 dB) or no gain (0dB) circuit. So, - at this point I think that the DCX can be used to do a dipole EQ requiring high gain shelving filters with no fear of clipping.

                                                            Regards,
                                                            Victor
                                                            Last edited by Victor; 10 December 2009, 23:39 Thursday.

                                                            Comment

                                                            • Saurav
                                                              Super Senior Member
                                                              • Dec 2004
                                                              • 1166

                                                              #31
                                                              I was playing with this earlier this morning, but that was the LspCAD Std demo where I can't save a project, so it was just a trial. I'll cross over to a monopole sub at around 80Hz, so I think 15dB of gain should get me what I need. I noticed that the LspCAD model maxed out at 15dB (so it looks like that mirrors the unit's capabilities, which is good) but I was able to get a relatively flat curve from 80Hz on up, with an LR4 HP at 80Hz. I also currently have an A500 on the woofers and a receiver on the mids/tweeters, so I could adjust the relative gain up and down within some range, which might help with the shelving requirements.

                                                              I think I'll have to keep a CX2300 in the mix to sum the two channels and provide the subwoofer LP, since I can't do stereo 3-way + sub with a single DCX (and I already have a 3200 and 3400).

                                                              Comment

                                                              • Davey
                                                                Senior Member
                                                                • Jan 2003
                                                                • 355

                                                                #32
                                                                Victor,

                                                                You're not limited to 15db EQ's with the DCX2496. You can cascade the sections to create pretty much whatever you want.

                                                                As an example, say you wanted a 20-320Hz 6db/octave shelving low-pass filter for dipole equalization. (That filter requires 24db of boost.)
                                                                You could create it in three different ways with the DCX2496 with each of three different level settings within the gain structure.

                                                                (6db/octave shelf setting in all cases, not 12db/octave.)

                                                                1.

                                                                -12db, 323 Hz, Hi Shelving.
                                                                -12db, 80 Hz, Hi Shelving.

                                                                2.

                                                                -12db, 323 Hz, Hi Shelving.
                                                                +12db, 20 Hz, Lo Shelving.

                                                                3.

                                                                +12db, 80 Hz, Hi Shelving.
                                                                +12db, 20 Hz, Lo Shelving.

                                                                Each of these settings yield an identical EQ curve, but level shifted within the gain structure to avoid possible clipping problems, or better match with mid-range, or whatever.

                                                                That said, I still think this type of usage compromises the performance of the DCX2496 quite a bit relative to an equivalent analog active circuit. A dedicated analog circuit can be very simple and has none of the potential issues a DCX2496 might have in this usage.

                                                                Hope that helps.

                                                                Cheers,

                                                                Dave.

                                                                Comment

                                                                • Victor
                                                                  Senior Member
                                                                  • Apr 2002
                                                                  • 338

                                                                  #33
                                                                  Originally posted by Davey
                                                                  You're not limited to 15db EQ's with the DCX2496. You can cascade the sections to create pretty much whatever you want.

                                                                  As an example, say you wanted a 20-320Hz 6db/octave shelving low-pass filter for dipole equalization. (That filter requires 24db of boost.)
                                                                  You could create it in three different ways with the DCX2496 with each of three different level settings within the gain structure.

                                                                  (6db/octave shelf setting in all cases, not 12db/octave.)

                                                                  1.

                                                                  -12db, 323 Hz, Hi Shelving.
                                                                  -12db, 80 Hz, Hi Shelving.

                                                                  2.

                                                                  -12db, 323 Hz, Hi Shelving.
                                                                  +12db, 20 Hz, Lo Shelving.

                                                                  3.

                                                                  +12db, 80 Hz, Hi Shelving.
                                                                  +12db, 20 Hz, Lo Shelving.

                                                                  Each of these settings yield an identical EQ curve, but level shifted within the gain structure to avoid possible clipping problems, or better match with mid-range, or whatever.
                                                                  Thanks Dave, - I kind of discovered the same thing, - with the choice #2 being what I needed. It indeed works. The responce of the DCX is the same as teh one I get from analog circuit simulations.

                                                                  Originally posted by Davey
                                                                  I still think this type of usage compromises the performance of the DCX2496 quite a bit relative to an equivalent analog active circuit. A dedicated analog circuit can be very simple and has none of the potential issues a DCX2496 might have in this usage.
                                                                  I agree it is qute easy to make an analog circuit. However, so far I have not seen any issues with the DCX that would make me not use it. I think with the mods DCX is right on the money. What issues are you seeing?

                                                                  regards,
                                                                  Victor

                                                                  Comment

                                                                  • Saurav
                                                                    Super Senior Member
                                                                    • Dec 2004
                                                                    • 1166

                                                                    #34
                                                                    Well, a friend at work just dropped off his DCX at my desk, so hopefully I'll get to play with it this weekend The guitar shop closest to me doesn't have XLR - RCA cables, which is a bummer. I guess worst case I could buy XLR cables and RCA connectors and make my own cables. I think I have enough to wire up one channel though, so while I won't have music, I should have something I can measure, which will be just as entertaining (for me, if not my family)

                                                                    Comment

                                                                    • chasw98
                                                                      Super Senior Member
                                                                      • Jan 2006
                                                                      • 1360

                                                                      #35
                                                                      Saurav:
                                                                      I might be bursting everyones bubble here about the DCX2496. I have one and have used it as a protyping tool for a few years now and it works just great. Once I have used it to protype a crossover and am happy with it, I have turned the digital model into an analog unit. I have found there is a marked difference between a top quality analog unit and the DCX2496. I don't really like it for daily listening but it is a great tool to use in building up a system and making a lot of small minor adjustements to a crossover.

                                                                      If you are planning to plug a plain old S/PDIF digital output into the digital input of the DCX2496 go to www.markertek.com and get the Canare transformer that will match your signal to the 110 ohm AES/EBU input of the 2496. Here is the part number BCJ-XP-TR. A BNC to RCA adapter will be handy also.

                                                                      As far as amplifiers go you might want to look into these Art SLA amplifers. I bought 3 of them for $200 each. They have balanced and unbalanced inputs, are rated at 100 watts per channel/8 ohms, and they sound pretty damn good for a $200 amplifier. http://pro-audio.musiciansfriend.com...ier?sku=484021

                                                                      I have just finished building a very flexible 4 way crossover for use with some line arrays I built. They were prototyped using the DCX2496 for over 6 months. The difference in sound when I put the new crossover in was very evident. But realize I am talking about a crossover that would retail for around $1,600.00. I bought my 2496 for $250. If you get a good deal on one, you will have a very versatile tool to use for this and future projects.

                                                                      Chuck

                                                                      Comment

                                                                      • Saurav
                                                                        Super Senior Member
                                                                        • Dec 2004
                                                                        • 1166

                                                                        #36
                                                                        Thanks. I've been playing with the borrowed DCX for most of today, and I can see how the transfer functions could be translated to an active analog XO without too much trouble (my previous XO was a mix of active and passive). Some of the transfer functions are practically impossible for me to do in a passive XO, especially if you throw in the impedance issues. As you said, I expect I'll be using this to experiment for a long time, before I might decide to build a 'final' analog XO.

                                                                        I have found there is a marked difference between a top quality analog unit and the DCX2496.
                                                                        Is yours stock or modded? I wonder how much of that is due to the DCX's analog sections, which everyone seems to feel are its weakest links.

                                                                        Comment

                                                                        • ThomasW
                                                                          Moderator Emeritus
                                                                          • Aug 2000
                                                                          • 10934

                                                                          #37
                                                                          I'll throw this is just to stir up trouble.....

                                                                          I've never been happy with the sound of my DCX, it's 'edgy' with a harsh, unpleasant 'bite' to the top end.

                                                                          But.....

                                                                          At this years RMAF Roger Sanders of Sanders Sound Systems was demoing his mega-buck ESLs and electronics with a DCX. As usual they sounded great.



                                                                          I asked Roger about the DCX he was using expecting him to reel off a mile long list of mods. Wrong! The internal electronics were all completely stock.... 8O

                                                                          Roger not only designs the speakers but the amps and preamps as well.

                                                                          IB subwoofer FAQ page


                                                                          "Complicated equipment and light reflectors and various other items of hardware are enough, to my mind, to prevent the birdie from coming out." ...... Henri Cartier-Bresson

                                                                          Comment

                                                                          • chasw98
                                                                            Super Senior Member
                                                                            • Jan 2006
                                                                            • 1360

                                                                            #38
                                                                            Originally posted by Saurav
                                                                            Thanks. I've been playing with the borrowed DCX for most of today, and I can see how the transfer functions could be translated to an active analog XO without too much trouble (my previous XO was a mix of active and passive). Some of the transfer functions are practically impossible for me to do in a passive XO, especially if you throw in the impedance issues. As you said, I expect I'll be using this to experiment for a long time, before I might decide to build a 'final' analog XO.



                                                                            Is yours stock or modded? I wonder how much of that is due to the DCX's analog sections, which everyone seems to feel are its weakest links.
                                                                            Mine is stock but I have opened it up to fix little things like the ribbon cables not making good contact and to poke around. I have used it with both straight digital in and with L/R analog in. The digital input sounded better but not by much. When you think about what Behringer has packed into a unit for so little money it is amazing it sounds as good as it does. But it is intended for pro PA use and not discriminating home systems. So when judging the unit to the Nth degree it falls short of the finest home gear but for most use it is incredibly good!

                                                                            I heard Robert Saunders system at RMAF and it was incredible with a stock DCX in it. But then I heard Emerald Physics units with a DCX in the chain and was not impressed. I don't know if you can attribute either system to having a DCX in it as being the good or bad item in the chain but I do think it shows that it can be implemented well or not so well. After living with mine prototyping for 6 months it was really nice to have it out of the loop and a better crossover in place.

                                                                            Comment

                                                                            • Saurav
                                                                              Super Senior Member
                                                                              • Dec 2004
                                                                              • 1166

                                                                              #39
                                                                              I'm just using the analog input for now, with a stereo volume control and source selector ahead of it (and the digital going into a DAC). The system does sound harder in the treble than what I'm used to, but I also recently replaced a SET amp with a 6-year old cheap receiver (driving the midranges and tweeters), and I'm pretty sure a large part of the change is due to that. I played with the gain structure a bit, trying to set it up so my normal listening level had the volume control up near the top (so I'm sending in as large a signal as possible), and then adjusting gain on the downstream amps. There's still a pretty big gain disparity between the channels, my tweeter is about 105dB, the midrange is about 95dB, and the woofer is about 90 and dipole to boot. If/when I go to a 6-channel amp, individual gain controls on the amp channels may be nice.

                                                                              I do have an issue with the left channel 'muting' randomly. Power cycling the unit was fixing it, so I thought it was flaky software (seemed like it happened a few seconds after I changed a setting). But then I was moving some stuff around and a bunch of the channels crackled, and now I can 'unmute' it by wiggling the cable in the back. The male XLRs going into the inputs seemed like they were a pretty loose fit. My female XLRs (for the outputs) are locking, but none of my male XLRs are - is that normal? Did anyone else feel the male XLR sockets were looser? AFAIK this unit was bought new and has been sitting in a garage for a couple of years.

                                                                              It also has a date code of 0303. March 2003, I guess. Have there been any hardware changes where I would be better off with a newer unit? I flashed the latest firmware on there.

                                                                              The reported hiss - my receiver has more hiss than my tube amp did, it's audible from say 1-2' in front of the horn tweeter. Turning the DCX on and off, I can't detect any change in the noise level. That too may change with a better amp.

                                                                              Comment

                                                                              • Victor
                                                                                Senior Member
                                                                                • Apr 2002
                                                                                • 338

                                                                                #40
                                                                                I do not know what would be the reason for the DCX to be less then very good, particularly once the modifications take care of its obvious shortcomings. The way I see it there are only two problems with DCX; - one is its input/output board and the other its digital input circuit.

                                                                                However, even in its stock from, it can work very well, providing you are lucky to get the unit that actually works as advertised out of the box.

                                                                                I have had 4 DCX units over the past 5 years and still have 2 on hand, - well, none of them worked well from get go, but I heard of many people never complaining about the problems that I saw and, frankly, many others saw as well.

                                                                                So, I would not unilaterally discount the DCX as a substandard product, because once the problems are fixed you have a unit that would outdo any, and I mean ANY, analog products on the market, particularly if the DCX were to be fitted with a passive output stage. I know it is a rather bold statement, but the fact remains that the digital implementation has none of the issues that any analog circuit would have, - starting with power supply noise, less then ideal capacitors in the signal path, non-linear phase issues, etc.

                                                                                Simply put the DCX can be made to achieve a near 19 bit performance in a real life environment, while the analog circuit, no matter what you try, will do that only on the test bench and inside the Faraday box.

                                                                                I am not trying to say that analog circuit is bad, - not at all, and, in fact, analog cross-over can be made to be superlative, but a digital circuit will have less issues, if done right, with all other things being equal.

                                                                                Finally, it seems that the digital implementation makes more sense, because we are dealing with the digital source to begin with. For example, in my HT the signal stays in digital domain all the way until power amps. The passive balanced output from the DCX, with its upgraded D/A converter, sees the Alps pots of the power amps and that is that for all 7 channels, although I only use 5 of them. I hope to do away with the Alps in the future and get a multi-channel relay-driven attenuator.

                                                                                Comment

                                                                                • CraigJ
                                                                                  Senior Member
                                                                                  • Feb 2006
                                                                                  • 518

                                                                                  #41
                                                                                  Originally posted by ThomasW
                                                                                  I'll throw this is just to stir up trouble.....

                                                                                  I've never been happy with the sound of my DCX, it's 'edgy' with a harsh, unpleasant 'bite' to the top end.
                                                                                  Hello Thomas,

                                                                                  I'll take that "bite" off your hands. Any chance you'd like to sell your edgy DCX?

                                                                                  Craig

                                                                                  Comment

                                                                                  • ThomasW
                                                                                    Moderator Emeritus
                                                                                    • Aug 2000
                                                                                    • 10934

                                                                                    #42
                                                                                    Craig

                                                                                    I use it for prototyping crossovers

                                                                                    IB subwoofer FAQ page


                                                                                    "Complicated equipment and light reflectors and various other items of hardware are enough, to my mind, to prevent the birdie from coming out." ...... Henri Cartier-Bresson

                                                                                    Comment

                                                                                    • Victor
                                                                                      Senior Member
                                                                                      • Apr 2002
                                                                                      • 338

                                                                                      #43
                                                                                      I had a chance recently to do some quick DCX measurements. Although I had an access to the THD analyser that was old and can only show 0.01% at best, still when the DCX is equipped with passive output, the measurement clearly better then 0.01%.

                                                                                      However if the original active board is put back, the measurement is subjectively worst, when you look at the meter, but I cannot say to what degree exactly. It could also be the same and is still very good, but it seems it is not as good as with a passive board. This is to be expected, since the power supply noise is not there and the rest of the active electronics is not in the signal path either.

                                                                                      So, clearly the DCX can be spectrally very clean. Unfortunately I had to use the DCX’s analog inputs and I am sure the results could have been better if a more modern digital-input equipped THD meter was available. Still 0.01% is nothing to sneeze at.

                                                                                      In contrast my hand-made active analog cross-over that I used to use with my Carver Mark IV speakers measures better then 0.01% but you can kind off see with the scope that it is not as clean as the DCX with a passive output. This cross-over has super low noise power supply regulators and AD797 op-amps along with some discrete op-amps, and all passives are top quality, so I know it is as good as it can be.

                                                                                      Naturally we are splitting hairs here, as both approaches will never be audible under any circumstances, but it is worth noting that the DCX, assuming that it works as advertised, modded or not is at least in the same league if not better then the best analog circuit that I can build.

                                                                                      Comment

                                                                                      • Dennis H
                                                                                        Ultra Senior Member
                                                                                        • Aug 2002
                                                                                        • 3791

                                                                                        #44
                                                                                        Originally posted by Victor
                                                                                        I had a chance recently to do some quick DCX measurements. Although I had an access to the THD analyser that was old and can only show 0.01% at best
                                                                                        Victor, if you have a good sound card, you can download the demo version of ARTA which will do everything except save files. The companion program STEPS does nice stepped-sine distortion measurements, subject of course to the native distortion of the sound card.



                                                                                        Attached Files

                                                                                        Comment

                                                                                        • Victor
                                                                                          Senior Member
                                                                                          • Apr 2002
                                                                                          • 338

                                                                                          #45
                                                                                          Dennis,

                                                                                          Interesting graph. It does kind of confirm the numbers I saw on that granddaddy of all THD boxes. The graph shows better then 0.01%. So this must be stock unit measurement, - right?

                                                                                          Well, with mods, particularly better output and better digital input we should see at least 5 times better numbers. By the way, the digital input on the stock DCX uses an IC that has a hardware problem. The manufacturer even issued the statement to that effect.

                                                                                          THis problem could result in noise and intermitent standing tones. THis will degrade the THD hugely. Anyway, I will try that ARTA-STEPS combo, - thanks.

                                                                                          Comment

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