New HQ DIY DAC

[Deleted]

Chris
This morning I tried a 22nF in place of the 100nF X2 capacitor and the CRO shows it is not as effective at reducing the rubbish.
When using 100nF , DTV via Toslink has lost a bit in the area of ambience especially, although Coax from the Oppo sounds a little better. It would appear that fitting an SPDIF transformer would need to be tried to see if there is any gain. I hope to try that in coming weeks.
With the JLHs in the SC DAC, the JLH that feeds +-15V to the DAC PCB should use a low ESR 4,700uF in parallel with a normal 4,700uF 16V electrolytic capacitor on each supply rail.JLHs for the digital area still have 2 x parallel low ESR capacitors on each rail.
Regards
Alex
P.S.
Checking that all RCA sockets on the SC DAC are not earthed to chassis is worthwhile,if it hasn't been done already.

[jeffc]

Hi Alex,

Interesting investigations and helpful pics as usual. I must revisit where I was with this DAC.

Luckily my old Rotel CDP used as a CD source has several dedicated linear supplies, so no AC to deal hopefully on the SPDIF gnd. But I must check what I used in the JLHs for the DAC I/V stage, but guessing all low ESR, so I should fix this as suggested, and add that thick extra gnd connection if I haven't done so already. I'll go fetch it from downstairs and have a look.

cheers.. jeffc

[Deleted]

Looks like I've finally brought my SC DAC up to date with ALL da mods maaan

( The only one missing is the recent 100nf X2 cap between spdif earth and chassis, left ahht 'cos I ain't got no chassis guvna! )

Anyway, I deliberately left the off-board xtal mod ( Jeff C very kindly sent me the CVXO what seems like an eon ago ) until last as it seems no one else had done so in that order and there was a little question mark over how much difference this mod made in its own right.

The off board xtal is on a recent home-bodged "cricket" that I adapted to take it, as per Wills circuit drawing.

The result?
More than I was expecting, whether it be the xtal, the extra clean psu for it or both.
There is a much stronger feeling of being drawn in amoungst the performers along with very "easy" feel. Everthing is present in bucket loads and extremely well balanced. I could throw in a few more superlatives but save to say it is all round better with zero "buts".
Well pleased

[Deleted]

Nov 26, 2012 20:17:53 GMT @cjarchez said:

Looks like I've finally brought my SC DAC up to date with ALL da mods maaan

( The only one missing is the recent 100nf X2 cap between spdif earth and chassis, left ahht 'cos I ain't got no chassis guvna! )

Anyway, I deliberately left the off-board xtal mod ( Jeff C very kindly sent me the CVXO what seems like an eon ago ) until last as it seems no one else had done so in that order and there was a little question mark over how much difference this mod made in its own right.

The off board xtal is on a recent home-bodged "cricket" that I adapted to take it, as per Wills circuit drawing.

The result?
More than I was expecting, whether it be the xtal, the extra clean psu for it or both.
There is a much stronger feeling of being drawn in amoungst the performers along with very "easy" feel. Everthing is present in bucket loads and extremely well balanced. I could throw in a few more superlatives but save to say it is all round better with zero "buts".
Well pleased

Hi Chris
You didn't miss anything by not trying that 100nF from SPDIF earth to chassis.It led me to finding that I had a left channel RCA socket where the earth side was framing to metal chassis creating a minor earth loop.
I didn't compare the difference between Xtal on board and a separate oscillator as Alfred and someone else assured me it was worthwhile.It shouldn't have made a difference in this implementation as the oscillator was only being used as a reference, but it obviously has .
Just wait until you have it working through the completed 15W Class A as well, as they appear to complement each other very nicely.
I use mine for all of my speaker listening, even for watching TV.
Kind Regards
Alex