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Labarum
20-03-2009, 08:23
This thread in another place makes interesting reading

http://www.computeraudiophile.com/content/First-Post-Cheapish-DAC

Quote from a knowledgeable member


The Valab is a simple DAC with no digital filtering. It literally has no output stage, just a stack of D/A chips. It is great sounding with a
low-jitter input and even better if you upgrade the output coupling
capacitors. For modding I recommend:

3.3uFd V-Cap oils bypassed with .22uFd Sonicap Platinums. These require some weeks of break-in BTW. This will be a world-class DAC with these caps. Not as good as my Overdrive, but beating most DAC's in the $10K range.

An I dont sell them either.

Steve N.
Empirical Audio__________________
http://www.empiricalaudio.com

No output filtering and no output stage - minimalist is often good. I wonder if you have to pair it carefully with an amp?

Academic, because I am not in the market for a DAC at the moment, but an interesting option.
leo
20-03-2009, 15:39
Fitting over $200 worth of coupling caps in the output:stalks:

Never heard the actual Valab dac personally but have built things using the same NOS stacked TDA1543's in parallel with passive I/V stage

Output drive should be pretty healthy with suitable I/V resistors, it would sound quite different to your TC-7510/20
Labarum
20-03-2009, 16:19
Fitting over $200 worth of coupling caps . . .

it would sound quite different to your TC-7510/20

$200 for four caps. Wow" That's some capacity upgrade!

Can you characterise "quite different", Leo?
Labarum
20-03-2009, 16:34
Oops.

The Forum Owner (the other place) squashes the idea flat!

http://www.computeraudiophile.com/content/First-Post-Cheapish-DAC#comment-15205
Labarum
20-03-2009, 16:37
Leo

Whats the idea of parallel DACs? Just to lower the output impedance and raise the current drive, or is there supposed to be some averaging of errors as the outputs merge in the analogue domain?

Would this be a good first DIY DAC project?
leo
20-03-2009, 18:28
$200 for four caps. Wow" That's some capacity upgrade!

Can you characterise "quite different", Leo?

Those caps are pretty expensive for such small values, using such a simple output stage the components used usually make more difference than a complex active stage.

I say quite different regarding sound because a multibit zero oversampled TDA1543 using no active output stage is NEVER going to sound the same as a unit using a oversampled CMOS Delta sigma PCM1716 with an op-amp output stage

Some may class the multibit based TDA1543 NOS as more analogue, fuller midrange etc , others may say it sounds less dynamic and more laid back compared to a more modern unit using a Delta Sigma

Its personal taste:)
leo
20-03-2009, 18:35
Leo

Whats the idea of parallel DACs? Just to lower the output impedance and raise the current drive, or is there supposed to be some averaging of errors as the outputs merge in the analogue domain?

Would this be a good first DIY DAC project?

Yes, parallel dacs increase current, it gives you more drive which is handy for passive I/V and making it suited to a wider range of pre/amps .
Downside is the increased heat, you'll notice parallel dacs with passive output stages tend to be heatsinked, they get pretty toastie especially the little TDA1543's
Also if one of those chips goes noisy it can be harder to trace

Would it be a good first diy project? well it depends, is this building from scratch on veroboard or buying some diy kit containing pcb etc?
Tom472
02-04-2009, 13:55
Whats the idea of parallel DACs? Just to lower the output impedance and raise the current drive, or is there supposed to be some averaging of errors as the outputs merge in the analogue domain?


As far as I'm aware there is error correction from averaging when multiple DACs are paralleled. There are designs with 4 or even 8 chips paralleled, and I read a long thread once about some kind of phase delayed multi-chip oversampling method - but I'm pretty sceptical about the merits of such a design.

Tom
nat8808
09-04-2009, 08:31
Is that what Stan Curtis did in the Cambridge Audio CD2, CD3 and DAC3 back in the late 80's with 1541A chip? Had 16x16 oversampling emblazened on them.
Tom472
09-04-2009, 16:20
Yeh I think the CD3 had 4 TDA1541A in it but don't know what the configuration was, or how it sounded. I'd love to have a go with one, but never seen one...