Where will it end?

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  • AndrewM
    Senior Member
    • Oct 2000
    • 446

    Where will it end?

    So I saw a post about DIY amps on another forum, and checked out some of the links that got posted and now my curiosity is getting the better of me. So I checked out something like Pass Labs Son of Zen project, the parts list is pretty small and it looks to be fairly simple to build/test. I'm just wondering what kind of results one could expect out of something like this? It looks to be an interesting design, scalable from 5-50 watts (by just pumping up the power supply), Class A operation, zero feedback, etc. My biggest worry would be how to dissipate the heat (build it to 50Watts and the power supply needs to be able to give 1200Watts all the time), look like it could heat a small room...or setup a home theater (5 channels) and heat the house while you watch a movie. Maybe yank the compressor and cooling stuff off an old fridge...hmmm

    Also, LCAudio has an amp kit out, but it's a digital amp, 90% effecient, big power (200+watts), small power supplies, low heat, etc. This one looks interesting, and is fairly cheap for what you could potentially get.

    I'm not so much looking for money savings, just something to do that's less messy then making sawdust. So how hard is it to construct some of these things? I have a bit of experience building kit based electronics (remember Heathkit?), but nothing to this magnitude, although I helped assemble the infamous DIY TV from I think Heathkit or was it Zenith, many years ago.

    Any comments?

    Andrew
  • Andrew Pratt
    Moderator Emeritus
    • Aug 2000
    • 16507

    #2
    well I know my musical fidelity class A/AB amp runs hot enough to keep my room warm Sounds like a fun project though.




    Comment

    • AndrewM
      Senior Member
      • Oct 2000
      • 446

      #3
      Well, 1200 Watts = 4096Btu's, which should add about a degree or two to the room I'd have the amp in. All of that from a 50W x 2 amp. So the idea of making 6 channels worth is probably not going to fly (don't want to have to upgrade the AC unit because of my audio habit)...the joys of inneficiency.

      It does look like a fun project, maybe something a little more "kit" like would be better for a first timer though, the AKSA looks interesting, but isn't a Class A amp (therefore doesn't need to be liquid cooled either). I think sometime today or next week Pass Labs will have put up his new DIY site, with more kit based items (instead of just 4-10 pages of information).

      Andrew

      Comment

      • JonMarsh
        Mad Max Moderator
        • Aug 2000
        • 15213

        #4
        This isn't a "hard and firm" recommendation, but I would think carefully about a Pass Labs or similar DIY project unless you at least have an oscilliscope, a function or audio generator, and some comfort with using them.

        What the Pass projects do well, is to demostrate the advantage of a very simple circuit- not necessarily an optimized simple circuit. After all, Nelson Pass is no fool, and there's reasons why he offered DIY designs at the same time as producing his Aleph designs.

        Simple circuits with low or zero feedback produce different colorations than more complex circuits using substantial NFB or un-optimized NFB and gain structures. In most cases, the colorations of the former are much less objectionable than the latter- they do less damage to the music, in a sense.

        Designs by Ayre, Theta Digital, and BAT are *not* simple circuits, and while still having minimalist gain stages and no feedback loop, have much better measured characterisitcs than the Pass Zen desings, as well as less component interaction. One drawback to the Zen designs using Power MOSFETs at the input is that they are sensitive to the driving impedance of the source, because of their high input capacitance. Don't use these with passive preamps or high output impedance tube preamps.

        Note that there are designs being produced by some which are advertised as being zero feedback, but which really aren't. Some of the Monarchy audio designs come to mind- also some Denon products. In this case, what they did was to build an output stage without feedback, and in the case of some of the Monarchy amps, drive them with a relatively high voltage op amp (Burr Brown OPA604 using feedback) in the front end. Now, this is hardly a crime, but the 604, like everything else, does have it's own signature to a degree. This is *not* a zero feedback amp in the sense of an Ayre V-5, for example, which doesn't have anything resembling a feedback loop - even on a local basis, Chas doesn't use a conventional Vbe multiplier for bias setting since he considers that a feeedback loop, however local.

        My Ayre and Aragon's do definitely contribute a room temperature rise; the Pass designs would do that, too. In the winter, that's actually nice, though not cheap with what it does to the utility bill if you listen a lot!

        Lastly, building chasis (for me) is just as much work and mess than building cabinets- maybe more, when you consider how nasty the metal particles are! So, lately, I'm looking at taking a commerical design available relatively cheaply with a nice chasis and replacing the guts. In fact, I've got a blown Quatre amp from the 70's on the way for just one such project, as well as a Denon monoblock I use as a chasis for experiments.

        I warn you, though- it's just like building speakers. Get some good results, and the next thing you know is you'll be justifying some more test equipment, or buying some transistors in bulk, or getting a drill press, well, you get my drift. I do this because it's my art; I don't do it to save money.

        BTW, if you want some pride of ownership and assembly without too much grief, I'd check out the Parts Connection Assemblage kits; you could do a whole lot worse than a system built with their vacuum tube line preamp, stero amp, and an Assemblage 2.7 or 3.1 DAC.
        Vist them at The Parts Connection.

        Best regards,

        Jon




        Earth First!
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        the AudioWorx
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        Comment

        • Lex
          Moderator Emeritus
          • Apr 2001
          • 27461

          #5
          hmmm, sounds like a fun project. I just picked up a beginer Electronics manual from Rat Shack, just to start learning a bit more myself in this area... You know, Resistance, capacitance, that sort of thing.

          Lex
          Doug
          "I'm out there Jerry, and I'm loving every minute of it!" - Kramer

          Comment

          • AndrewM
            Senior Member
            • Oct 2000
            • 446

            #6
            Well, the scope isn't that big of a problem, although it's probably been 10 or so years since I've used one (and for computer repair work not audio). The audio or function generator could be an issue.

            It's interesting that you brought up the chassis part of the whole thing, because I totally forgot about that part of it until I started reading a thread about heat sinks for the Son of Zen and the associated chassis the whole thing would need. It's kind of interesting some of the things people come up with to cool those things down, water cooling...somebody was throwing around the peltier idea, etc. And I've seen some really nice chassis ideas, and some very ugly one's as well. So I could just see the eyes rolling back of the lady friends head when I tell her I need metal working tools to go with the wood working tools.

            Actually the ST40 kit looks interesting, it has more than enough power for my needs (if I ever get off my duff and finish building those Focal's), and it doesn't at least from the reviews have to much of that "tube sound". Hmmm, maybe a good start to another endless cycle of the DIY audio world. Although if I keep up the DIY side of things, I won't have a store bought component in the system.

            So Jon, how do you think those Digital amp kits (like from LCAudio) would sound? Sounds almost to good to be true, getting 200+ watts of power from a tiny power supply, flat from DC to 100Khz, board the size of a credit card. So is this the free lunch the audiophile world is waiting for?

            Andrew

            Comment

            • JonMarsh
              Mad Max Moderator
              • Aug 2000
              • 15213

              #7
              The Sonic Frontiers tube stuff has always impressed me as being built to a high standard of neutrality, not to a tweakish standard of tube sound. That's where the roots of the Assemblage stuff is from.

              We were joking on another thread that what I really needed (with my X1 Klones) was just a good 25 watt amp, due to their efficiency; the ST-40 would meet that criteria handily.

              The 2.7 and 3.1 Assemblage DACs are also first class as separate DAC's go; they use the Burr Brown 1704 converter, which is probably the best true PCM converter in the world, especially when paired with the DF1704 digital filter. That combo was available in the 3.0 with the upgrade board. It's also used in my favorite DVD/CD player, the Ayre D1. Now Assemblage uses the PMD200 as the digital filter; I don't have any familiarity with it, I guess I just have to trust that they've made a good choice, as most of their other design decisions and offerings seem to bear out. BTW, the OPA627 Op amps should be a mandatory upgrade for these DAC's; they're the only Op Amp I've used in my own designs in primary signal path the last several years; if you have to go with an integrated discrete audio op amp, I think it sounds the best. YMMV.

              I have looked at LCAudio's web site, but they dont' really have enough information about their designs to make much of a judgement. Switching frequency is pretty standard - 500 kHz in most cases- and that's too low for a 100 kHz single inductor filter, which they use. I've dabbled in Class D over the years, and written a few papers on the work I've done- PCIM, AES, that sort of thing. Class D amps are less of a challenge now than years ago because of the tremendous improvements in the semiconductors, both integration of control functions and power devices. Yet, some of the same problems with output filter interaction with the load, and HF noise remain.

              I've played around more recently with the TriPath stuff, and if I can get a box together, will assemble a 400W/channel stereo amp I've cobbled up. Actaully, I've got a "broken" Quatre Gain Cell amp on the way which is a virtually completely sealed chasis, using the whole chasis as a heatsink, and it may be a good testbed for that, if there's enough room for the Plitron power transformer and Philips caps I've got. It's setup with a conventional power supply, just as Crown mates conventional supplies with their K series Class D amps. I've done a switching power supply design for a Pro Audio amp; the problem is the complexity, and the fact that unlike a computer, which has relatively steady demands, an audio amp has demands which go all over the place. A commercial switching power supply will current limit at 10% over the rated power, whereas a line transformer and cap setup can deliver on a short term several times the rated continuous power.

              Plus, you have to take some special care to isolate EMI, and to filter the HF spike ripple and common mode noise that can be conducted due to capacitive coupling from the switching transistor heatsinsks. It's a nasty set of problems.

              Which brings up another point- Gerald Stanley's Class D output stage (used in the Crown amps) is probably the most elegant and bullet proof around- more so than the TriPath or others. They have some good white papers on the Crown site, so I won't bore anyone here by rambling on about that. I keep telling myself when I get a little extra time I'm going to mate my old digital front end to a power block using his circuit, but finding that time seems to be a problem.

              Right now I'm listening to the 40th Anniversery Jacque Loussier album (Play Bach- jazz interpretations of Bach) on a new bookshelf speaker I've built (Eton woofer and Accuton tweeter), through the Ayre V-5, and the HF sound on the cymbols and piano is just to die for- which motivates me to drag out a dual differential zero feedback design I was simulating three years ago and build that, instead of the Class D whizzbang which will probably only wind up being a sub amp. But maybe not; I haven't made any final listening judgements, and a lot of people like the Evo amp based on the Tripath modules.

              The more I play with zero feedback circuits, and listen to them, the less inclined I amp to put an op amp in the signal path, or a conventional feedback loop. Maybe I'm just fooling myself, and doing some kind of hoodoo voodoo on my ears and my head, but it's hard to argue with what I'm hearing. Sometimes we have to make progress in spite of ourselves and our previous biases. I've gotten perturbed enough by the whole thing that I've started designing a DAC to build which I can run off my 777ES as a transport, separating the digital and audio portions, just so I can play with different signal amplifying topologies, then routed just through my passive preamp and V-5 into the speakers. I don't really think the digital part can be good enough to compete with the SCD777ES on CD (though it is a 24bit/96 kHz oversampling delta-sigma (one bit) DAC), but then I won't have all those OpAmps Sony uses in the I/V stage, output filter, and output buffer. So who knows? It should be interesting.

              If I had to make a "musical bet" sight unseen, sound unheard, I'd put my money on the Assemblage gear over the LC Audio. But I could be wrong.

              Let us know what you decide to do.

              Best regards,

              Jon




              Earth First!
              _______________________________
              We'll screw up the other planets later....
              the AudioWorx
              Natalie P
              M8ta
              Modula Neo DCC
              Modula MT XE
              Modula Xtreme
              Isiris
              Wavecor Ardent

              SMJ
              Minerva Monitor
              Calliope
              Ardent D

              In Development...
              Isiris Mk II updates- in final test stage!
              Obi-Wan
              Saint-Saëns Symphonique/AKA SMJ-40
              Modula PWB
              Calliope CC Supreme
              Natalie P Ultra
              Natalie P Supreme
              Janus BP1 Sub


              Resistance is not futile, it is Volts divided by Amperes...
              Just ask Mr. Ohm....

              Comment

              • JonMarsh
                Mad Max Moderator
                • Aug 2000
                • 15213

                #8
                One other point-

                Although I'm not convinced about LC Audio's Class D module, I've looked over their other offerings, and I'd say they're very interesting for a DIY upgrade or build it yourself approach. I think their explanations for why some things sound different with their zero feedback amplifier circuits may be pitched a bit simplistic and aren't the whole story by any means, but they do seem to offer some intersting products, with good thinking behind them. In particular their CD player upgrade modules are interesting and convincing in execution, based on my experience and preferred principles.

                I may buy a couple of their clock modules to retrofit my Sony Players. It's odd to come across such similar thinking for their audio circuits in some where as far away as Scandanavia, but then ThomasW, the Salt Cod Oil Baron, would approve!

                Also, since they're just set up DIYCABLE.COM as their distributor, getting the stuff should be a little easier. DIYCABLE.COM is worth checking out for their offerings, too. They carry some of the more reasonable priced Cardas connectors, and advertise they can get any Cardas parts at 20% off list. Hopefully that includes the Cardas Quad Eutectic solder.

                Regards,

                Jon




                Earth First!
                _______________________________
                We'll screw up the other planets later....
                the AudioWorx
                Natalie P
                M8ta
                Modula Neo DCC
                Modula MT XE
                Modula Xtreme
                Isiris
                Wavecor Ardent

                SMJ
                Minerva Monitor
                Calliope
                Ardent D

                In Development...
                Isiris Mk II updates- in final test stage!
                Obi-Wan
                Saint-Saëns Symphonique/AKA SMJ-40
                Modula PWB
                Calliope CC Supreme
                Natalie P Ultra
                Natalie P Supreme
                Janus BP1 Sub


                Resistance is not futile, it is Volts divided by Amperes...
                Just ask Mr. Ohm....

                Comment

                • EMT
                  Member
                  • Aug 2000
                  • 44

                  #9
                  Jon, are you at all familiar with the kits from Seal Electronics?

                  Ellen

                  Comment

                  • AndrewM
                    Senior Member
                    • Oct 2000
                    • 446

                    #10
                    Hmmm, I think it's time to flip a coin here. I've pretty much ruled out the Pass DIY offerings, at least for now. I think they're a little to far advanced for my rusty skillset, except maybe the Son of Zen project, but there are more than a few challenges on that project as well, like trying to get rid of 1200+ watts of heat (without having to resort to dry ice).

                    So I'm trying to decide between the AKSA kit and the Parts Connection kit. On the cost side, it's proabably about equal. Assembly wise, the Parts Connection kit is a no brainer, everything is included so it's just a matter of soldering it all together, do a little testing/biasing and you're good to go. The AKSA you at least need to source some parts (but it's all documented where to go for what). Quality wise when you're done, it's kind of hard to read, both are very popular kits and have been for awhile (always a good sign), and actually if you read the comments from those who have built them the performance is around the same level. The AKSA will handle various speaker loads a little easier, and has a little more power (I have effecient speakers, so this is a semi-non-issue).

                    Ahhhh the decisions....

                    Andrew

                    Comment

                    • JonMarsh
                      Mad Max Moderator
                      • Aug 2000
                      • 15213

                      #11
                      Seal Electronics appear to offer good value kits with well designed circuitry that would be considered state of the art in the 70's, and contemporary in the 80's. The PCB design layout looks quite competent and well executed.

                      They have an FAQ page which explains their design philosophy- which is based on a fairly objectivist approach from the 70's. Now, I'm not trying to say that he's wrong because he's old fashioned- it's just that there are very different philosophys at work here, and I have to take substantial issue with a number of Mr. Slone's statements, particularly those about why solid state sounds better than tubes, about why high feedback is no problem, and about how one can't hear differences between amplifiers if designed to a certain standard of performance with regards to THD.

                      I'd probably have to say there was a time I might have had some similar views, and I've certainly been caught out in short comings in my own thinking and philosophy when confronted with what I thought was correct, as compared with what I and others actually hear.

                      He would never believe, for example, that you could hear a significant difference in HF and midrange clarity between a very well designed "conventional" amp like an Aragon 8008BB, and an unconventional zero feedback design like Ayre's V-5. On ThomasW's "mid-fi" family room system, using only a CD player (no SACD rigamorole tossed in! ), the difference are not subtle, and they're not subtle in my home system, either, since I bought my own V-5 after the audition last summer. By Mr. Slone's philosophy, what we heard wasn't possible. When I put the V-5 in the top end of my home system, without mentioning anything, my girlfriend wanted to know what I'd changed since she last heard the system.

                      Most of Seal's design's use electrolytic caps in the feedback loop as well as in the input connection. This has been a romper room no-no for me since the mid seventies, and my own listening tests from that time. Even his new Opti-MOS designs (an Infineon trademark) (he's not talking about the same kind of FET, though) use elec. caps in the signal path, input and feedback.

                      His signal topologies are well executed, well known techiques, but fall short of the optimizations possible on a stage by stage basis, regarding sabilization and linearization of the transfer function under all signal conditions. For example, the last conventional design I did used a differential cascoded JFET input stage, using multiple matched monolithic pairs, with an active self biased load using Precsion Monolithics MAT-02 monlithic pairs, buffered with another monolithic pari to a high current differential voltage gain stage run in cascode, with a five transistor modified Wilson current mirror connected with a cascode to convert the signal to push pull. The differential output stage and current mirror included anti-saturation clipping limiters. The output module used lateral MOSFETs made in the UK as a class A driver, and four chip modules using the same lateral MOSFET chip in modules as the output device. The output stage has less than 0.01 % THD and IM with no loop feedback, because it was a compound design with the main outputs working as current dumpers for the class A drivers. You could drive this output stage open loop from a conventional op amp, with surprisingly good results. (this was a design done under contract for a small pro audio company).

                      My recommendation is to understand what you're looking for, and if possible, listen before purchase. If your requirements are such that you know you can use the module as is in some application, like a sub or something else where midrange and HF transparency are not critical, then getting a module to evaluate for all kinds of applications is not risky.

                      You might want to take a look at LCAudio.com, since DIYCABLE will be handling their stuff. They have some module kits which in my opinion are very well designed, and apparently have won them some awards for their performance. With a US distributor in the picture, this would not be so risky. Their PCB layouts and construction seem pretty good to me. However, I haven't hard there stuff either, but I feel more sympatico to their design philosophy.

                      Maybe some other forum memebers can chime in their thoughts.

                      Best regards,

                      Jon

                      Anything else I might say is just speculation, because I haven't heard any of the Seal Electronic kits. I can speculate that they probably sound fairly decent, certainly as good or better than a high end receiver, for example. Where they fall in the bigger picture would be hard to say- only possible with listening. And the pricing appears attractive for the construction and component quality.

                      He's also a good source of parts, it seems for those interested in rolling their own, but without a ready source for audio style heatsinks, caps, etc. And his protection control board for a power amp would be interesting to a home contructor, also.




                      Earth First!
                      _______________________________
                      We'll screw up the other planets later....
                      the AudioWorx
                      Natalie P
                      M8ta
                      Modula Neo DCC
                      Modula MT XE
                      Modula Xtreme
                      Isiris
                      Wavecor Ardent

                      SMJ
                      Minerva Monitor
                      Calliope
                      Ardent D

                      In Development...
                      Isiris Mk II updates- in final test stage!
                      Obi-Wan
                      Saint-Saëns Symphonique/AKA SMJ-40
                      Modula PWB
                      Calliope CC Supreme
                      Natalie P Ultra
                      Natalie P Supreme
                      Janus BP1 Sub


                      Resistance is not futile, it is Volts divided by Amperes...
                      Just ask Mr. Ohm....

                      Comment

                      • EMT
                        Member
                        • Aug 2000
                        • 44

                        #12
                        Jon,

                        Thanks so much for taking time out to compose such a thorough, informative and interesting reply. I found it to be quite helpful.

                        Ellen

                        Comment

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