1. Shunting the main tanks makes sense in systems
nutrition.
If you want to use better quality decoupling capacitors, you can use either very high quality ceramics
with maximum linearity, or WIMA 1uF 63V film, but MANDATORY
with the recalculation of the entire LPF scheme for this denomination.
What you did is wrong! The sound will be too bright!
2. OPA1688 cannot be used in the subtractor stage and simultaneously as a headphone buffer.
You did it wrong!
For correct operation, a faster amplifier is needed in the subtractor,
then, with decoupling, install the AD8397 repeater, or with a maximum ku = 1.3. Then the amplifier will work without distortion for a low-impedance load.
3. Replacing the inductors in the power supply makes sense only when
you are sure that you put the inductors with the best quality factor.
Are you sure you have delivered better inductors?
4. Capacitors in the power supply are also selected with certain characteristics, I'm not sure what you supplied.
Excuse the long post, but I will be quoting your statements so as not to cause confusing. I really appreciate your comments, they are very educational. I know it can be frustrating answering noob questions.
"1. Shunting the main tanks makes sense in systems nutrition."
- I am not sure I understand this statement.
"If you want to use better quality decoupling capacitors, you can use either very high quality ceramics
with maximum linearity, or WIMA 1uF 63V film, but MANDATORY
with the recalculation of the entire LPF scheme for this denomination.
What you did is wrong! The sound will be too bright!"
- Which decoupling capacitors are you referring to? Originally, I was talking about the 100uF coupling caps on the hpf located right after the DAC.
"2. OPA1688 cannot be used in the subtractor stage and simultaneously as a headphone buffer.
You did it wrong!
For correct operation, a faster amplifier is needed in the subtractor,
then, with decoupling, install the AD8397 repeater, or with a maximum ku = 1.3. Then the amplifier will work without distortion for a low-impedance load."
- Okay this is good information! Thank you! I used the OPA1688 because I saw someone here who used OPA1622 as both subtractor and buffer and since the difference between the OPA1622 and OPA1688 is not that much, I thought I could do the same. My question is, how about using OPA1612 for subtractor and OPA1622/1688 as buffer? I happen to like how the TI op amps sound.
"3. Replacing the inductors in the power supply makes sense only when
you are sure that you put the inductors with the best quality factor.
Are you sure you have delivered better inductors?"
- The only factor I considered is the DC resistance of the inductor. Other than that, the amperage rating. The one I used has a rating of 1.9A and about half the DC resistance of the one that was in the Zishan originally. I assume it is better overall. Here is a link:
https://www.mouser.com/ProductDetail/Bourns/SRR3818A-4R7Y?qs=EU6FO9ffTwfji0kq1pAYtg==
"4. Capacitors in the power supply are also selected with certain characteristics, I'm not sure what you supplied."
- I used Panasonic ultra-low ESR caps. They are the FR series.