Good set up for A and B
Great opportunity to compare MODs and offer believable feedback. Please give internet location of the OPA 660 circuit.
Reliable observers have reported NOS TDA1541 as the best 16 bit DAC chip once modded appropiately. But you seem ambiguous about it? You are using a 780X at the output of your power supply, most others are using TL 431 to regulate and decouple. Perhaps this would help? Also although the specs of the OPA 660 look impressive is it the best opamp for this purpose? Perhaps better to have used a socket to allow exchange of opamps for comparison. AD825, AD 8065, OPA 627, 637 browndog adapted to dual status seem to be the most regarded chips for the output.
Your gear is more than adequate for comparisons. Are your Altec monitors using a Compression driver and horns? They can be very dynamic and forward but accentuate the HF while lacking extreme HF output .
Questions remain:
Best output opamps (in your gear)
NOS vs OS
Both CDPs must be modified identically and only the one difference being compared allowed to vary for the test to be reliable.
Other suggestions for mods down the line:
Separate PS with TL 431 to new clock, DAC, and output section
Transformer volume control and Tube output plus many others.
Check Lesha's DAC site at the bottom for other good sites and ideas.
Keep up the good work and keep us informed
Great opportunity to compare MODs and offer believable feedback. Please give internet location of the OPA 660 circuit.
Reliable observers have reported NOS TDA1541 as the best 16 bit DAC chip once modded appropiately. But you seem ambiguous about it? You are using a 780X at the output of your power supply, most others are using TL 431 to regulate and decouple. Perhaps this would help? Also although the specs of the OPA 660 look impressive is it the best opamp for this purpose? Perhaps better to have used a socket to allow exchange of opamps for comparison. AD825, AD 8065, OPA 627, 637 browndog adapted to dual status seem to be the most regarded chips for the output.
Your gear is more than adequate for comparisons. Are your Altec monitors using a Compression driver and horns? They can be very dynamic and forward but accentuate the HF while lacking extreme HF output .
Questions remain:
Best output opamps (in your gear)
NOS vs OS
Both CDPs must be modified identically and only the one difference being compared allowed to vary for the test to be reliable.
Other suggestions for mods down the line:
Separate PS with TL 431 to new clock, DAC, and output section
Transformer volume control and Tube output plus many others.
Check Lesha's DAC site at the bottom for other good sites and ideas.
Keep up the good work and keep us informed
Please use SEARCH function.
No,I use 7805 for current injection.The preregulators for OPA660 317/337 are used and finally regulation is done by TL431 ,as in original Thorsten schematics.
OPA 660 is not regular op amp and you can't substitute this with regular op amps.It is I/V converter + buffer,please see PDF for it.
As to NON-OS vs OS I wrote my opinion and observations in my original post.
All Best
Bartek
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