a few years ago I used to upgrade the holman preamps.
They are old enough now that a full recap would be a good choice.
There are two short falls with the Holman pre amp.
1. a tiny power supply transformer
2. the TL072 texas instruments op amps.
Both can easily be corrected. Tons of choices out there now for dual op-amps. Same with transformers. I would normally leave the original in place and bring in the secondary wiring from the new transformer into the unit.
The apt pre also uses quite a few electrolytic caps to couple the stages together. These should all be bypassed with a film and foil cap.
And if you really want to go wild, you can Vishay the whole signal path resistors with the metal foil types.
best
They are old enough now that a full recap would be a good choice.
There are two short falls with the Holman pre amp.
1. a tiny power supply transformer
2. the TL072 texas instruments op amps.
Both can easily be corrected. Tons of choices out there now for dual op-amps. Same with transformers. I would normally leave the original in place and bring in the secondary wiring from the new transformer into the unit.
The apt pre also uses quite a few electrolytic caps to couple the stages together. These should all be bypassed with a film and foil cap.
And if you really want to go wild, you can Vishay the whole signal path resistors with the metal foil types.
best