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OLD THREAD DAC End by Andrea Ciuffoli

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#1,842
Because the new DAC boards uses different parts and is in fact a different project then the first does anyone else feel like we should start a new thread to assist builders of this new and hopefully improved DAC instead of piggybacking on this old thread??

Thanks!
 
#1,844
Salas said:
I see no output capacitors. Is it using the local decoupling capacitors on the chips as output capacitors? Integrated regs on board with the chips? Without output capacitors would be very wrong. At least 47uF and enough ESR.
Click to expand...

Hi Salas,

When you say "enough ESR" does this mean that using low-ESR 'output' caps such as Rubycon ZA or OS-CON SP could upset the regs? Better to sling in some higher ESR caps?

Best regards,

Neil
 
#1,854
Yomanze said:
Hi Salas,

When you say "enough ESR" does this mean that using low-ESR 'output' caps such as Rubycon ZA or OS-CON SP could upset the regs? Better to sling in some higher ESR caps?

Best regards,

Neil
Click to expand...

Super low ESR caps are going to significantly worsen its transient step response by shortening its gain with frequency and by twisting the closed loop phase hard. Now I can't tell whether the digital chips get it worse with higher ESR because I haven't delved in to this DAC, but in this version the decoupling between chips in very high frequencies should not particularly suffer since there is a battery of dedicated regs (if the grounding and stray inductances help too). Thus I would lean into picking ESR to suit better the regs. At least plain vanilla caps are everywhere and cheap.
 
#1,855
Salas, I'm very curious about this. I've been working with the Audio Note board for 10 years. This last one built from scratch eliminating filter networks I used super low impedance caps which resulted in a much cleaner yet still NOS sound. As the audio slang goes as if a veil was lifted. However, on the DAC chip itself (C29)I recently went to a 270UF with a .1uF film cap bypass and the results were better dynamics, soundstage and low level detail. Mid bass greatly benefited. The cap I used was a Black Gate but I'm sure a good OSCON would bring the same result.
 
#1,856
That answer was about how the specific reg is designed for closed loop gain and how it terminates best. If average ESR caps upset the chips worse than super low ESR upsets the regs, then the only way to know is to fit a set of mid quality caps and a set of royal quality caps and listen to it. I can't make any further assumptions when I don't know the DAC design peculiarities or the layout parasitics.

That AN example surely did not have multiple regs of this type and did not use its B+ decoupling elements as reg terminals also. So experience from it can't come directly enlightening our question. The question is which of two fighting optimums will prove more influential subjectively in this kit.
 
#1,858
Salas. I just talked to my transformer builder and he may be able to sneak it in to this weeks run otherwise its a 8 week wait.

I recall being told or ready the PT secondary is 6 pairs of 9VAC @ a TOTAL of 200mA? Is that correct? Or is it 200mA PER 9V winding? IE 200mA x 6 = 1200mA total for the AC secondary?
 
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