BUILD THREAD - A New Take on the Classic Pass Labs D1 with an ESS Dac - Page 49 - diyAudio
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Old 28th January 2013, 01:26 PM   #481
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It would seem logical to build and listen before critiquing, but what do i know. I am just a greenhorn.
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Old 28th January 2013, 01:32 PM   #482
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Quote:
Originally Posted by qusp View Post
you clearly dont have much of an idea of how the ES9018 works then, you wont 'just' get a small increase in 2nd harmonic.

Please clue me in. Preferably with numbers.
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Old 28th January 2013, 01:36 PM   #483
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at the very least you would want to try and load both outputs the same

seriously why do I have to list out numbers in such an obvious case, everything including the internal layout of the dac and external pin layout, roughly $500 or more (for half) and more again if you include power supplies, all in primo symmetrically matched components tagged onto the output of 2 balanced dacs and then not using it? does that have to be spelled out for you?

just use a transformer, there are several other options but a couple of edcor or even onetics output TX arent that expensive and dead easy to implement, nothing compared to the cost of having so much sitting there completely idle

if you look, weve been through this conversation at least 5 times already (probably significantly more) in this thread.

Last edited by qusp; 28th January 2013 at 02:02 PM.
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Old 28th January 2013, 02:02 PM   #484
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Originally Posted by qusp View Post
seriously why do I have to list out numbers in such an obvious case, everything including the internal layout of the dac and external pin layout
Because it has nothing at all to do with the internal layout of the dac per example. Clearly both outputs of the 9018 are loaded the same, so it is only a question of less output voltage and even harmonics not being cancelled. So, what is this? 6db worse s/n and let's say distortion up to -100db? How on earth does this matter in the context of a 300B amp? It probably isn't the best choice for an I/V stage for a non-balanced amp, but maybe one day there will be a proper balanced amp in his system.

It somehow annoys you that someone may be misusing your favourite toy, but it is the most sensible and practical choice in the situation.
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Old 28th January 2013, 02:14 PM   #485
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why is it the most sensible? it has just as much to do with the internal layout of the dac as any of these other carefully engineered symmetrical things that end in naught. the most sensible is following it through, its got nothing to do with my favorite toy, its got something to do with answering a shitload of questions and selling this man a bunch of expensive matched stuff, that would be completely without meaning if only half the output was used.

I would have also strenuously advised against such a large expense, the blame for which was placed squarely at my feet a few pages ago by BPHK along with some amount of expectation.

btw BP I know you arent the one pushing for this

if the plan is to fairly quickly replace those amps then sure maybe, but otherwise going the rest of the way is a drop in the ocean compared to the rest of the effort and expense.

Last edited by qusp; 28th January 2013 at 02:27 PM.
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Old 28th January 2013, 04:05 PM   #486
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There are some rough measurements of taking the SE output from one phase of the NTD1 back in the main thread...

Start reading from here:

A New Take on the Classic Pass Labs D1 with an ESS Dac

Calvin built an early iteration of the circuit and claimed he was getting terrible results... turned out it was because he was measuring SE out.

The THD+N penalty is significantly higher than 6dB... think more in the order of 20-30dB.

Honestly, I would suggest using just one phase as a last resort, and trying pretty much anything else to see what sounds best.

If the next stage were an F5 with SE input, then I would definitely go the op-amp route, but with a tube amp, a transformer might be a little more in-line with the sonic signature of the amp itself.

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Old 28th January 2013, 04:19 PM   #487
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just a quick note/reminder about balanced systems, it is mainly even harmonics as far as THD (from the chip) that are cancelled in a summing stage, but with a completely differential circuit and dac like this, just using one half means you lose ALL the CMRR and that isnt just 6db THD.... rather any common mode error, ripple, noise etc. that would previously be deleted wrt the rejection ratio; shows up in its entirety without a summing stage.

Given this Dac chip and everything after it was designed with this summing in mind (they do not even supply any spec for without the summing) the effects could be severe, the big picture cannot be known without knowing the power supply, grounding, noise on USB etc.

it will not be 6db.

remember also the fairly low PSRR of the circuit, but with everything in place and pretty much constant draw its not a significant issue

Last edited by qusp; 28th January 2013 at 04:30 PM.
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Old 28th January 2013, 04:27 PM   #488
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ahh yes I remember that convo Owen, I knew there was something more concrete and we have covered this ground several times but I forgot the rough measures you made.

from memory (bed time for me) we found out he was using a different dac too wasnt he? lol like the pcm1794 or something? or was that another early detractor?

Quote:
Originally Posted by opc
If the next stage were an F5 with SE input, then I would definitely go the op-amp route, but with a tube amp, a transformer might be a little more in-line with the sonic signature of the amp itself.
my thoughts exactly

Last edited by qusp; 28th January 2013 at 04:35 PM.
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Old 28th January 2013, 04:31 PM   #489
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I was indeed planning on flipping the phase of DACB and trying it Vout SE into a tube amp. With tube specs in the 0.1% THD, I wouldn't think it matters (the increased THD) would it?.

But I agree, transformer is probably the simplest solution. Way, way back there were some recommendations for low cost (and good for audio) transformers. Anyone remembers?
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Old 28th January 2013, 04:46 PM   #490
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no, glt I saw your musings on that but resisted at the time =) but I would think it would be subject to exactly the same limitations, but you would get some small amount back from the parallel dacs being added.

SNR and DNR will also be effected I would think and some of the THD and noise will be coincident with the series THD in the tube amp (dont ask me how much. All this was enough for me not to give it any more thought.

if you do a search for posts by me and Russ (may have been Brian, but memory says Russ), I think in one of the early legato threads (or at least in the TP forums here at DIYA), I made some posts along a similar line to what you are suggesting, but with the Ackodac.

None of your solutions for FW control were available and the Buff had limited functionality in this area at that time, the ackodac was the only DIY dac capable of it then. I was pretty green and was corrected pretty completely with info in-line with what we are saying here.

as for transformers I can recommend the ones from BudP O'netics, as a quality but not crazy priced part (maybe $50 each from memory) Pano also made high recommendations and quite a few posts on Bud's units for dac output. if still interested i'll see if I can track down a datasheet, or you could PM BudP here on the forum. they are high nickel core with copper wire, custom wound. very good spec and seem to be also highly regarded in the F6 thread. normally you would pay a lot more for such units but Bud isnt quite as well known as the usual high dollar options. Edcor are also good for something cheaper as I said earlier.

Last edited by qusp; 28th January 2013 at 05:15 PM.
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