DIY mono amp for the Wavecor Ardents

[TEK]

Hi

Starting this thread because I'm playing around with the idea to build two monoblocks to
power my Wavecor ardents.
The monoblocks will replace mu current Thule 350B amp - and A/B amplifier delivering 350w@8ohm x2.
http://www.audioholics.com/amplifier...e-audio-pa350b

The target is that the monoblocks should be an improvment to this amp that will get other duties, most likely to drive the surround channels (or be sold).
I have build some electronics before (my wavecore crossover, a bottlehead pre-amp and some other stuff, but this will be my first amplifier - so I'm looking for something that is fairly easy to build. And something that I belive there are resoirces to ask for help if nessesarly.

For now I'm evaluating building something based on tge following:
Holton 500L/800L, a 350/500w @8 ohm AB construction

http://holtonprecisionaudio.com/collections/amplifier-module/products/nxv800

(Recommende and good access to knowledge)

Holton 50L, possible x2, a 50w (100 if 2x) @8 ohm pure class A construction

http://holtonprecisionaudio.com/collections/amplifier-module/products/hpa-nxa50l-pure-class-a-amplifier-module

Hypex nc400, possible x2, a 200w (400 if 2x) @8 ohm class D amplifier

https://www.hypexshop.com/DetailServlet?detailID=4466

Anyone having some onput regarding this?

Updated summary from this thread:
Here I will update my findings for the final amp as the tread progresses and I figure out stuff.

BOM:
Power supply: 1 x SMPS1200@400 (per amp)
Amplifier module: 2 x Hyped nc400 (per amp)
Transformer (Jons tweak): Jensen JT-6110K-B
Case: http://www.modushop.biz/site/index.p...product_id=444
47u 200v Cap for bridging: ?
47r resistor to eliminate dc: ?
Inputs: 2 Balanced XLR
Output: 2 Speakon speaker cabel connectors

About the case
I selected this case because I like the looks of it, and it is not expensive. At the same time there is a norwegian group buy from modushop, so I guess there will be some discount.
This case was evaluated, but not choosen as it was quite expensive compared to the selected case:
Case: http://www.ebay.com/itm/Pair-GK-ASP-...e&talgo=origal

[Jonasz]

Look at the Anaview AMS1000 also, uses the same technique as the big Maarten monoblocks.

[JonMarsh]

i have been in my past lives a designer of high performance linear power amps for professional applications, both with bipolar and lateral MOSFETs (Hitachi, and British made copies of the Hitachi FETs). I'm up on all the current theory from guys like Douglas Self, Bob Cordell, Charlie Hansen (a friend and former employee at one time) and have also done non negative feedback designs. Plus, I've listened to a lot of stuff... a lot. Also done vacuum tube stuff. This doesn't make me an expert, but it does mean I've been around the block.

If you like heatsinks and big hardware, go for one of the Holton designs. A little overkill on power, and remember, 500W is only 3 dB more than 250W . If you want something cool running, small and convenient, not a space heater in the summer time, very low noise and low THD in the range it really matters (up to 50W), go with an nCore 400 with Hypex SMPS600 power module for each 400. A nice complete chassis setup for small mono blocks is available on eBay, from Ghent Audio.

http://www.ebay.com/itm/321584525441?_trksid=p2057872.m2749.l2649&ssPageNa me=STRK%3AMEBIDX%3AIT



Images not available

If you want to hot-rod the nCore, get a Jensen 6110 transformer and use that on the input, and change out the gain set resistor on the nCore to up the forward gain 3-4 dB to make up for the step down effect of the 6110. The 6110 has very high input level capability and very low distortion, and properly setup will give you huge common mode isolation between each amp and your source. It's my favorite tweak for nCore. I can give you details.

[BobEllis]

I'll throw up another class AB option - the "Honey Badger" over at DIY Audio. Boards for amp, power supply, soft start and speaker protection available in their "store". They sell a version of an HIFI2000's enclosure that looks great that you can order directly. They don't sell circuit boards to Europe, but if you'd like I'll reship them for you. Just PM me if you want to go that route. For Chassis http://www.diyaudio.com/store/custom/hf2korder.php

I have a Honey Badger that I am using as my main amp now. It is a little cleaner with somewhat better imaging than the Leach Amp that it replaced driving a Zaph designed 2 way with Seas Excel drivers (W15CY and T25). I went with dual power supplies off of a single transformer. Somewhat scalable, at nominal 60V rails it will give you around 125-150W and can go higher with appropriate output devices. If you use the MJL4281/4302 pairs you can probably run 75 volt rails and get close to 300W peak. I used the Toshiba devices listed as the first choice. I'm no expert, but it seems like it's a riff on Self's Blameless topology.

I'm looking forward to rolling amps when I get my Wavecor Ardents completed. I'll bring out my upscaled Pass/Thagaard A75 and as well as completing the Pass Aleph-J and F5Turbo. My A75 bests an old Leach, but the version I'm running now is much better than the original Leach. I haven't pulled out the A75 to compare it to Leach or Honey Badger. Pass amps are space heaters, but well regarded. I suspect that the AlephJ and F5Turbo will be a bit underpowered for the Ardents, though.

[TEK]

Thanks a lot for your input Jon.
"go with an nCore 400 with Hypex SMPS600 power module for each 400"
I have seen quite many state that a SMPS600 can be used to drive 2 ncore 400, giving you 400w instead if 200.
Should I read your post ad this is not a good idea?

From what I understand about the transformer it is an addition, meaning I could start with a easy build and then update, right?
Would I need a bigger chassie them the one you linked to?

Also, my understanding is that you think that there will be littke significan sound difference between the holton class A amp and the ncore409?

[oneplustwo]

I already have built a pair of Pass Aleph X monoblocks and an F5 but with the remodel, space is at a premium so these nCore amps are compelling. Might be time to sell off the Class A stuff as much as I love them! And the build of these with the ebay cases would be super easy! Looking forward to seeing what you decide.

[benthe8track]

If you want to hot-rod the nCore, get a Jensen 6110 transformer and use that on the input, and change out the gain set resistor on the nCore to up the forward gain 3-4 dB to make up for the step down effect of the 6110. The 6110 has very high input level capability and very low distortion, and properly setup will give you huge common mode isolation between each amp and your source. It's my favorite tweak for nCore. I can give you details.

Do you think this is worth adding to mine? I need to go into it anyways to try a different VU driver board. Also I'm supposed to be working on a case for another one for an unspecified old man in Winnipeg haha.

Thanks a lot for your input Jon.
"go with an nCore 400 with Hypex SMPS600 power module for each 400"
I have seen quite many state that a SMPS600 can be used to drive 2 ncore 400, giving you 400w instead if 200.
Should I read your post ad this is not a good idea?

I used one SMPS1200 to drive two NC400s. It was a bit more soldering but not bad at all.

https://www.htguide.com/forum/showthread.php?41876-Hypex-NC400-Build

[TEK]

Thanks a lot for the link ben - a lot of info in that thread.
It seems like your and others valuable input have helped me decide on the road to travel.

My current idea is to go with two ncore based mono amps.
But just building a regular ncore amp seems a bit "dull" for a DIY build so I'm looking at he following solution:
2 mono amps
Applying bens vu-metere tweak
Applying Jons transformer tweak
Both singel ended and balanced input
Maybe support switchable inputs - so I can switch between my receiver for theater and a dedicated pre-amp for stereo - possible remote comtrolled - must figure out what is needed to support such a solution
Maybe a 12v trigger

Have to select the ncore parts. Wondering about using 2 ncore400 pr. mono amp...

[dar47]

Okay Jon we know you don't have time to build it but maybe you can do a quick drawing layout as I'm sure confused. Not sure where that goes in the case? It's looks to be a $100. US tweak.

[JonMarsh]

Will try to get to that this weekend- totally swamped at work what with reviews and being asked to step in for a guy out on three weeks medical leave when my own stuff is not getting attention or time. A lot of unrealistic pointy hair management going on...

[TEK]

Anyone know how to connect/wire two ncore 400 to get one mono amp?

I also see that a single smps600 is a bit little to drive two ncore400, so I will need two smps600 or one smps1200. Guess there is little reason to not go for a single smps1200..

[benthe8track]

Anyone know how to connect/wire two ncore 400 to get one mono amp?

I also see that a single smps600 is a bit little to drive two ncore400, so I will need two smps600 or one smps1200. Guess there is little reason to not go for a single smps1200..

This is how I did it:

Document not available

[TEK]

This is how I did it:

Document not available

Thanks a lot ben!
I assume that is how to connect the smps1200 to the nc400.
Thats great - and now I have that part of the puzzle :-)

Yours is a stereo amp while I'm planning on a mono amp.
So I still have to figure out how to bridge the two nc400 together.


I have to admit that I'm a bit forth and back regarding using two nc400 is worth it, but I do think that if I can go with the smps1200 and two nc400 the extra cost would be the second nc400 (smps1200 and smps600 cost the same). Chassie, connections and all other would be the same. In that regard - I think it would be a good deal to get a 400w@8ohm instead of 200w@8ohm amp...
On the other hand, a monoblock with a smps600 driving a nc400 is a pretty sweet thing as well I expect.
One tiny consern is that hypex states that the smps1200 is for their udc modules while the smps600 is for the nc400. Based on bens experience that seems to be more marketing talk than anything else

[BobEllis]

A web search turned up this, although I'd suggest verifying with Hypex.

I haven't seen specific instructions for NCore but Hypex says it is the same as for the UcD series.
So, for a typical balanced connection, bridge tied load (BTL):
* hot(+) signal to amp module A hot(+) input and to amp module B cold(-) input
* cold(-) signal to amp module A cold(-) input and to amp module B hot(+) input
* connect the speaker load between the two positive amp outputs. Typically amp A would be the + side, amp B the - side. They recommend a 47nf cap across the output in that case. Note that NO output grounds (-) are connected.

Here is the wording from the Hypex UcD400 FAQ just for reference. I don't know how the impedance/current protection limitations would specifically apply to the NCore 400/SMPS600. The data sheet does rate them to 580w at 2 ohm loads (for 4 ohms bridged operation, with suitable power supply). I would also be sure the offset is properly adjusted in both.

UcD bridging

Q: I need double the power in an 8 Ohm load than a UcD amplifier can produce. Is there some way I can bridge two, for example, UcD400’s?

A: You need to drive one of the modules 180 degrees out of phase by simply swapping the negative and positive input signal wires. Tie the loudspeaker between both positive loudspeaker outputs of the amplifiers and connect a 47n/200V capacitor across the loudspeaker terminals at the amplifiers’ side. This set-up is most applicable for 8 Ohm loads since each amplifier ‘sees’ 4 Ohms with an 8 Ohm load attached. A 4 Ohm load might trigger the current protection leaving you with not nearly as much power as you might have expected.

[TEK]

Thank's BobEllis. I have seens that as well.

I'm a bit thrown off by this statement "This set-up is most applicable for 8 Ohm loads since each amplifier ‘sees’ 4 Ohms with an 8 Ohm load attached. A 4 Ohm load might trigger the current protection leaving you with not nearly as much power as you might have expected."

If that is the case I have to say I'm wondering if the effort and cost of using two nc400 makes it worth it. Maybe it would be better to just stick with a single smps600 + nc400 pr. monoblock.
That may explain why I'm having hard time finding examples for people who is actually bridging two nc400 together.

Thoughts anyone?

Edit: bridged nc400 with smps1200a400: http://www.audiocircle.com/index.php...858#msg1188858

[BobEllis]

Without going too deeply into it, bridged amps send a signal to the load that is twice what it would be for normal operation. That results in twice the current in the load, or THEORETICALLY 4 times the rated power at that load impedance (there are a lot of arguments over the semantics of this on other forums, I hope I don't start that here). When is theory not the same as reality? When the current is limited by either the power supply, output stage device capability or protection circuitry kicks in. Say for example that your amp is designed to safely deliver 5 amps (200 W into 8 ohms), and with a little headroom the current limiting protection circuit kicks in at 7 amps. Bridging such an amplifier would limit you to 7 amps, and you'd only get 392W before the protection circuit kicks in, not the theoretical 800 W. Same result if your power supply is limited to less than 10A total. Neither seems to be the case with the NCore or SMPS1200, as the amp modules are specified to operate into 2 ohms. The current limiting comment may be a remnant of the UCD module that this comment originally applied to.

However, is bridging worth the extra cost? Looking at the THD+N vs. power curves in the data sheet, I'd say that you should get pretty close to the theoretical 800 W into 8 Ohms cleanly. That's only 6 dB louder than 200W, but gives you that much extra headroom. My theory is that clipping behavior is a big factor in the sound of amplifiers with music. If your average level is 1 W and the music delivers a 30 dB peak you will clip any amplifier not able to deliver 1000 W. Just 25 dB crests above 1W would require over 300W to avoid clipping. Clipping would only occur on extreme peaks, and may not be objectionable. The Wavecor Ardents are nominally 8 ohm speakers, into which the NC400 can deliver 200W. Your musical tastes determine whether that's enough. You want to listen to the 1812 overture at live levels? You probably should bridge. Quiet jazz trios you thing? A single NC400 will be plenty. Most Rock is so compressed that you need a lot less peak power than you'd think to rock out. I think one of the original Wavecor Ardent builders built an NC400 based amp with room to add additional modules and hasn't seen the need to update.

[JonMarsh]

The SMPS1200 supply for the UcD's is somewhat lower voltage (+/-65V nominal) than the SMPS600, which is about +/-74V. There are charts for how to wire up a SMPS1200 to NC400 modules; just takes a bit of splicing, as opposed to just plug in the supplied harness.

For me, I don't think I need that extra SPL, and if I do, I'll break out the Isiris.... and you're definitely right about compressed rock and pop; not all that high a peak level. But classical, or stuff like Harry James big band is another matter.... another 10 dB or so is not unreasonable.

[meb46]

Jon... the Isiris should be your daily listeners!

I have been playing around with Amplifiers on my versions... normally I run a Rotel RB-1092 (2x 500W into 8ohms and something near 2x 1000W into 4ohms). This powers mine well, but as we all know, the ICE modules that Rotel uses, and Rotel's implementation is "Clinical" sounding. The problems with these is two fold, a) Clinical sound, and b) The speakers chew up the power in an amazing fashion. Bear in mind, I use my big three-ways in a very large room size and have no shame in the volume in which I listen to them at. I tried my Bel Canto M300 Power amps the other day as a comparison, and the difference was phenomenal... phenomenal in terms of the lack of power. The difference between 300w versus the Rotel 1000w was tremendous. I know the extra db increase is minimal between the two, but clipping/distortion/headroom is a huge factor. Long story short, I won't be powering the big three-ways with anything less than what the Rotel RB-1092 can throw at them. This naturally starts to limit my options... but something I continue to try and nut out moving forward.

[TEK]

The SMPS1200 supply for the UcD's is somewhat lower voltage (+/-65V nominal) than the SMPS600, which is about +/-75V

Is that difference something that is expected to have a negative effect?

[BobEllis]

It could limit your peak power somewhat in normal mode into high impedance loads. In bridged mode you'd still have plenty of voltage swing (effectively double) so there would be no power limit due to voltage. If the ncores can swing to within 10 volts of the rails then 65V rails would limit you to around 190W RMS into 8 ohms. I don't know how close to the rails they can get, but within 5V would get you rated power on 65V rails.

[TEK]

The difference between 300w versus the Rotel 1000w was tremendous. I know the extra db increase is minimal between the two, but clipping/distortion/headroom is a huge factor. Long story short, I won't be powering the big three-ways with anything less than what the Rotel RB-1092 can throw at them. This naturally starts to limit my options... but something I continue to try and nut out moving forward.

When you are getting into these kinds of power ratings, would it not be a good idea to go over to using bi-wiring and bi-amping? I don't know what it takes to redo the crossover to support bi-wiring, but I assume there are a lot of others here that do know.
That might as well be an option for the Wavecor Ardents - but not that nessesarly.

It could limit your peak power somewhat in normal mode into high impedance loads. In bridged mode you'd still have plenty of voltage swing (effectively double) so there would be no power limit due to voltage. If the ncores can swing to within 10 volts of the rails then 65V rails would limit you to around 190W RMS into 8 ohms. I don't know how close to the rails they can get, but within 5V would get you rated power on 65V rails.

From here: https://www.hypexshop.com/DetailServlet?detailID=4466
They say: "HV bus voltage +/-35V to +/-72V"
I assume that should mean that the voltage different should be no problem. But they do also say "Available output power depends on supply voltage", supporting what you said BobEllis. If I understood your calculations correct I should expect to see a total of 380W RMS into 8 ohms, while if I had gone for two SMPS600 I could have expected a total of 400W RMS into 8 ohms.

And here http://www.hypex.nl/docs/NC400_datasheet.pdf
In chapter 5, Recommended Operating Conditions and Supply Currents
They say "Power supply voltage: 35 (min), 64 (typ), 75(max)"


Seems like this is doable. The picture below is from this thread (referenced further up): http://www.audiocircle.com/index.php...858#msg1188858
As noted before you need a 47n 200V cap to bridge them. From the picture below that is clearly not ClarityCap ;-)
Anyone know what kind of cap that can be suited for this usage?



I see that hypex in some cases (ref. page 15 of the manual) recommend "Strap 47k across the RCA input to provide DC path" in some cases. But what wattage should that resistor be? Anyone have a clue?

[BobEllis]

Close, TEK. RMS power is 1/2(V^2/R) You'll theoretically get 380W peak at 55V, but the RMS power will be 190W. Also, take a look at the THD+N vs. power curve at section 9.2. It looks like hard clipping at just under 300 W, although they don't specify rail voltage or load.

Bi-wiring is easy with the Wavecor Ardent should you choose to do it. Just take the mid and tweeter crossovers to one set of terminals and the woofers to another. More effective would be actively biamping the woofer to mid/tweeter crossover. (See http://sound.westhost.com/bi-amp.htm) That would allow smaller amplifiers if that crossover is around 300 Hz, and open more options should MEB want to try other amplifiers.

[JonMarsh]

OK, time to get some adult supervision to prevent somewhat off topic posts, but if I can get away with it, I feel this may be a good spot for some light reading on a Friday morning.

Not DIY.



But quite interesting- finally shipping, and Stereophile has a very interesting review in the issue I just got...

This amplifier was first announced in 2012, and got a fair amount of publicity (though not shipping) in 2013. Signal to noise ratio and dynamic range is approaching 130 dB, which is equivalent to about 21 bit resolution.

No where near as large as this picture makes it look- 11" wide, 3.84" high, 9.34" deep. 12.5 lb. Just 100W@8 Ohms, 200W at 4 Ohms. Switching resonant mode power supply (no current square waves, but sine waves, as I'm working on for the IR team) power supply, linear amplifier using feedforward, a collaboration between Benchmark and THX.

This thing is so quiet and clean that it is pretty much at the limits for what a Audio Precision can resolve- in fact, one of Atkinson's speaker test cables was introducing more distortion than the amplifier... but he figured that out. Great Scott!

The audio circuit is basically a low bias AB linear amp combined with a feedforward stage for error correction.

100mW THD+N is about 0.0006%, and from there it drops to 0.0001% at 3.5-3W, and stays there right up to clipping.

Marty, this is heavy- really heavy- clearly something has affected the earth's gravitational forces!

Balanced input connectors are provided, and ONLY balanced inputs are provided, as well as one which can be used to drive the amplifier as a bridged mono block, and a dedicated AMP-ON output for balanced bridge mode. Great Scott!



Can't cut and paste any graphs yet, because while in the current issue magazine, the review is not up on the web site.

This is the first "analog" amp I've seen in ages that gives the nCore stuff a run for the money spec wise. In fact, probably the only one that does, as regards dynamic range and distortion.

[TEK]

OK, time to get some adult supervision to prevent somewhat off topic posts, but if I can get away with it, I feel this may be a good spot for some light reading on a Friday morning.

Not DIY.



But quite interesting- finally shipping, and Stereophile has a very interesting review in the issue I just got...

This amplifier was first announced in 2012, and got a fair amount of publicity (though not shipping) in 2013. Signal to noise ratio and dynamic range is approaching 130 dB, which is equivalent to about 21 bit resolution.

No where near as large as this picture makes it look- 11" wide, 3.84" high, 9.34" deep. 12.5 lb. Just 100W@8 Ohms, 200W at 4 Ohms. Switching resonant mode power supply (no current square waves, but sine waves, as I'm working on for the IR team) power supply, linear amplifier using feedforward, a collaboration between Benchmark and THX.

This thing is so quiet and clean that it is pretty much at the limits for what a Audio Precision can resolve- in fact, one of Atkinson's speaker test cables was introducing more distortion than the amplifier... but he figured that out. Great Scott!

The audio circuit is basically a low bias AB linear amp combined with a feedforward stage for error correction.

100mW THD+N is about 0.0006%, and from there it drops to 0.0001% at 3.5-3W, and stays there right up to clipping.

Marty, this is heavy- really heavy- clearly something has affected the earth's gravitational forces!

Balanced input connectors are provided, and ONLY balanced inputs are provided, as well as one which can be used to drive the amplifier as a bridged mono block, and a dedicated AMP-ON output for balanced bridge mode. Great Scott!



Can't cut and paste any graphs yet, because while in the current issue magazine, the review is not up on the web site.

This is the first "analog" amp I've seen in ages that gives the nCore stuff a run for the money spec wise. In fact, probably the only one that does, as regards dynamic range and distortion.

hmm, 3000 usd...

http://benchmarkmedia.com/products/benchmark-ahb2-power-amplifier

But still want to build my ncores ;-)

[Steve Manning]

Can't cut and paste any graphs yet, because while in the current issue magazine, the review is not up on the web site.

This is the first "analog" amp I've seen in ages that gives the nCore stuff a run for the money spec wise. In fact, probably the only one that does, as regards dynamic range and distortion.

Jon do you have a scanner that has OCR ability? You could go that route if you do.

[JonMarsh]

Hmmm. You're right, I do. But the graphs are printed so small in the print edition of the magazine, and there's a lot of bleed through from the other side of the page.

If I have time at lunch, I'll research this some more and post some. I'm not bringing this up as a candidate for these DIY situations, but just because it's a very interesting level of performance and probably redefines what one can expect at $3K. Not as much power as an M22, but pretty damn impressive performance. I'm going to have to put this on my XMAS list for certain!

BTW, when I mentioned it approaches 130 dB SN, that's the unweighted number. Doing the usual A weighted evaluation, it's in the range of 132-135 dB. Great Scott! You could make phono preamps out of these!


Here's some more background about the THX technology (one of the inventors is the brother of Andrew Jones, the former TAD top speaker engineer):

http://www.stereophile.com/content/h...J27up4rlvlJ.97

[JonMarsh]

Consider this a teaser trailer provided by another forum member who should probably go nameless and blameless-



And go out and buy a copy of the current issue of Stereophile- it's a good issue overall, and this review alone makes it worth the money, IMO. YMMV, of course!

A couple of these in bridged mono mode would be pretty dang righteous on a set of Wavecor Ardents! (see the far right graph- bridged mono into 8 ohms) :T :B ;x(

[TEK]

...
Seems like this is doable. The picture below is from this thread (referenced further up): http://www.audiocircle.com/index.php...858#msg1188858
As noted before you need a 47n 200V cap to bridge them. From the picture below that is clearly not ClarityCap ;-)
Anyone know what kind of cap that can be suited for this usage?

Do you think this will work?
https://www.elfaelektronikk.no/elfa3...q=47+capacitor

[5th element]

Those Benchmark amplifiers are certainly impressive. SMPS too so its voltage rails will hold up far better under load and regardless of the line voltage too.

[ergo]

This Twit episode has an interview with one of the designers of the AHB2 - quite interesting

https://twit.tv/shows/twit-bits/episodes/836

[JonMarsh]

Using the 6110 Transformer

OK, some details about how one might use the 6110 transformer in an NC400 build.

First, part of how this transformer optimizes the S/N ratio and distortion is that it is a STEP DOWN transformer, by a factor of 4:1, designed to handle inputs up to nearly +30 dB. The application circuit below is one of several for it- it's also recommended as a coupling output for differential DAC's, as it provides both filtering at 120 kHz and high CMRR as well as very wide bandwidth -3 dB at 0.15 Hz and 120kHz.

IF you have a preamp capable of high output levels, say, 8VRMS, there's no reason you can't use this in the chain with a NC400 module, because you can drive the transformer to the input level necessary for the total gain to still clip the NC400. Many solid state preamps will do this fine, but you'll see the volume knob cranked up, maybe as high as the 2 or 3 o'clock position. This actually tends to optimize the S/N through the whole chain, because most preamps (there are a few exceptions, like the top of the line Ayre, or the Mola Mola, ) have worse S/N with the volume control set for attenuation, as the output stage is fixed gain, with most of the gain of the preamp occurring there.

If you have a preamp that can't output 8VRMS, then you need to change the value of the Rg gain resistor R141 on the NC400, if you change it from 680 ohms from the original 1200 ohms, then in concert with the feedback resistors, (which are balanced) the net gain increase is 12 dB. You could also go for something intermediate.

This shows you how to do the calculation.



Below is the typical wiring diagram for using the 6110 with a single ended input; for the balanced inputs of the NC400, you want to just connect the series transformer outputs to the +/- inputs.




It's VERY important to connect the white and black leads to the signal ground of the NC400 module; these are the transformer shields and establish the output CMMR reference point. DON'T connect them to the chassis!

DO terminate the output of the 6110 into a 2.2K metal film resistor in parallel; this provides optimum loading for the transformer for cleanest impulse response, and provides a low noise source impedance to the amplifier even when nothing is plugged in, and is multiplied by the square of the turns ratio (16) as presenting the effective input impedance.

I don't even recommend installing the grounding switch, but DO put the 51 ohm resistor and a good HF (ceramic or stacked film) bypass cap in series to the chassis ground, for RF shielding and terminating the shield at the amp. DON'T connect the shield directly to the chassis - this leads to the possibility of forming an AC ground loop.

The 6110 is supplied in a shielded mu metal can, with a clamp for mounting to the chassis.

[TEK]

Jon, thanks a lot for that great input!

With two nc400 bridged in a monoblock, would you only need one 6110 or would you need two?
Earlier in this thread you wrote:

The 6110 has very high input level capability and very low distortion, and properly setup will give you huge common mode isolation between each amp and your source

Could you elaborate a bit on the expected effect of this?

[JonMarsh]

You only need 1 6110; just wire both inputs to the output of the 6110, but wire one channel with reversed phase.

The transformer provides additional isolation between the Class D amp and SMPS power supply and the rest of your signal chain. Subjective effect is clearer imaging and cleaner transients, assuming good source gear and a good room setup.

I'd like to think I'm some kind of out of the box thinker, but I found out last summer that the AURALiC Merak's use this concept too, with their $2500 UCD mono blocks.

[TEK]

Thanks Jon.
I have "requested" two (one pr. monoblock) from Jensen. Will just have to wait and see if my "request" is given a positive reply ;-)
But I WILL need some help down the line to translate your input into actual wires and components :-)

[JonMarsh]

Thanks Jon.
I have "requested" two (one pr. monoblock) from Jensen. Will just have to wait and see if my "request" is given a positive reply ;-)
But I WILL need some help down the line to translate your input into actual wires and components :-)

no problem, that's what I'm here for- actually, it's pretty straight forward. But then I am a wires and sparks guy, since 10 (shortwave radio), not really a wood worker!

[TEK]

If you have a preamp that can't output 8VRMS, then you need to change the value of the Rg gain resistor R141 on the NC400

Jon, is there any way around this that does not require midification of the NC400?
I assume such a modification would woid the factory warrent - and that is not preferred. At the same time I would like to be able to drive the amps with a "regular" preamp.
Especially as this is a part of a multichannel setup and these amps must be in the same ballpark as the rest of the amps used.

[JonMarsh]

Then the best likely way around this is to use one of their other transformers, such as I'd been considering for a from scratch Class D amp I've been working on. Not quite as wide bandwidth, and won't have the sort of impedance transformation that gives the edge in SN.

I'll get back to you tomorrow with a part number or two.

What kind of multi-channel electronics are you using? Is this mostly for HT, or for music too?

[TEK]

Hi Jon
I'm currently using a Marantz SR7005 receiver.
As the Ardents have a lover sensebility than the center/sorround speakers the left and right channel is already adjustet up quite a bit (12 db or so I think)
I do play around with the idea of in the future adding a separate stereo DAC and preamp that will be used in paralell with the receiver for music listening. But I do not know what that would be yet.

[TEK]

Have any of you herd about "NewClassD"?
There is some talk about these solutions in norway - and some seems to be very impresssed and mean these solutions is as good - or better (mostly better) than the ncore modules.

http://www.newclassd.com/index.php?page=44&curip=5

[BobEllis]

I haven't heard it but some observations from the data sheet:

Linear power supply. Subject to line variations and rail sag under load.

Calls for 2 x 40 VAC transformer. That will give you nominally 55V rails. Even if it swings rail to rail and they don't sag, that's not going to get you rated power. As a DIY project you are free to over specify the transformer but it seems odd that they call for an 800 VA to deliver 800W. I'd go 1,200+ if I was going to build an 800W amp.

Filter caps rated 63V. A bit on the close rated side for some. If the transformer delivers the typical 5% higher than rated voltage at no load and the line runs high you could exceed the cap's rating. Of course this also means that you can't go with a 45V transformer to get rated power.

[TEK]

So to translate to legmans terms:
The specs seems to have some week points (that - my assumption - the ncore does not have?

[BobEllis]

Yes. As 5th Element mentioned a switch mode power supply like the nCore has will hold its rail voltages better. The NewClassD may deliver 200W into 8 ohms on 65V rails but not with the specified power supply (the power difference isn't likely to be audible but I wonder about products with obviously impossible specifications). It may sound wonderful, though.

[JonMarsh]

I haven't heard it but some observations from the data sheet:

Linear power supply. Subject to line variations and rail sag under load.

Calls for 2 x 40 VAC transformer. That will give you nominally 55V rails. Even if it swings rail to rail and they don't sag, that's not going to get you rated power. As a DIY project you are free to over specify the transformer but it seems odd that they call for an 800 VA to deliver 800W. I'd go 1,200+ if I was going to build an 800W amp.

Filter caps rated 63V. A bit on the close rated side for some. If the transformer delivers the typical 5% higher than rated voltage at no load and the line runs high you could exceed the cap's rating. Of course this also means that you can't go with a 45V transformer to get rated power.

Actually, Bob, you're being a bit on the generous side. Because of the regulation issues for the transformer, I normally recommend and have used 2X the output power for the VA rating of the transformers. One can optimize the power extraction through a large filter reservoir; +/- 50K uF is a good working range. 63V DOES seem a bit on the under-rated side, as for nominal input voltage (115VAC usually used for transformer ratings), those caps will see 40X 1.414, minus the forward drop of the rectifiers, which puts one very close to 62-63V. Of course, if you have high AC line voltage, like we often do where I live now, or in Colorado where I used to live, with 120VAC, it's pushed a few volts higher. Electrolytic caps do usually have some surge margin, above their rating, but that is surge, not continuous- it will increase the leakage current, and could affect the capacitor operating life or reliability. I'd normally be using 80V caps in this situation. Especially if one goes with a 45VAAC transformer.

There are a lot of people on the market offering power supplies or rectifier/cap assemblies that can be used with linear or Class D amps; just should probably look further afield. I've looked at some of the switches; (have several samples on hand); many are not as well engineered as the Hypex products. Bruno's team dot's the i's and crosses the t's.

[JonMarsh]

I have heard/read some positive things about NewClass D also, but it would be nice to see a good report on them with an Audio Precision. If they can measure well enough to quote a low THD spec (no frequency specified), and with their wide claimed power bandwidth, it seems they ought to be able to provide that kind of information, as Hypex does.

[BobEllis]

I normally go 2x for class AB but fudged down a bit for class D. Interesting that you maintain the 2x margin. You're the pro, so I'll follow your lead if/when I go class D. My class A amps' transformers are rated for 4x idle dissipation.

You could probably just put higher rated caps in that PSU but you'd also have to watch the input limit on the regulator for the logic circuits. Not to mention the cost/ availability of 80V caps that big.

Unknown performance and some odd choices at a premium price vs known outstanding performance at a significantly lower price. I know which way I'd go.