I have been gradually restoring and tweaking a PAS 2 over the last several weeks. Replaced the can cap, swapped the rectifier for some diodes, and recapped the stock circuit. The first modification I made was removing the tone controls from the circuit, following the Audio Regenesis instructions, including the 1 uf caps to block DC from the preamp outputs. This mod didn't seem to affect the sound too much, but I didn't ever use the tone controls anyways.
The biggest issue I had with this preamp was the volume imbalance due to mistracking in the volume pot. I ordered this ALPS 250k pot (no affil) and wired it up. I had to cut about 1/4" off of the shaft with my angle-grinder so that the knob fit correctly. It doesn't have a loudness tap, so I just disconnected all of the components for the loudness.
I had read that this was a suitable replacement part, but it sounds terrible at anything but low level listening. The highs get really harsh and the bass muddy, and even at normal listening levels it hurts my ears. I have read elsewhere that removing the loudness tap can change the load presented by the original volume pot + loudness, but I am not sure how to correct for that. I read as much as I could find about this subject, but there is a lot of conflicting information out there about replacing these volume controls. The volume on this new pot also increases really quickly as well. It's a smoother volume control than the original, I just know something is off.
I have also seen many suggest that you can use a 100k pot that comes with loudness tap to replace the original 250k pot, but that it messes with the phono section because of the change in load presented. I really only use the phono section, and I don't want to make all of the modifications laid out by some to "fix" the phono section's RIAA errors or whatever. I think it sounded fine with the old volume pot, but I want to get rid of the imbalance! Thanks for any help.
The biggest issue I had with this preamp was the volume imbalance due to mistracking in the volume pot. I ordered this ALPS 250k pot (no affil) and wired it up. I had to cut about 1/4" off of the shaft with my angle-grinder so that the knob fit correctly. It doesn't have a loudness tap, so I just disconnected all of the components for the loudness.
I had read that this was a suitable replacement part, but it sounds terrible at anything but low level listening. The highs get really harsh and the bass muddy, and even at normal listening levels it hurts my ears. I have read elsewhere that removing the loudness tap can change the load presented by the original volume pot + loudness, but I am not sure how to correct for that. I read as much as I could find about this subject, but there is a lot of conflicting information out there about replacing these volume controls. The volume on this new pot also increases really quickly as well. It's a smoother volume control than the original, I just know something is off.
I have also seen many suggest that you can use a 100k pot that comes with loudness tap to replace the original 250k pot, but that it messes with the phono section because of the change in load presented. I really only use the phono section, and I don't want to make all of the modifications laid out by some to "fix" the phono section's RIAA errors or whatever. I think it sounded fine with the old volume pot, but I want to get rid of the imbalance! Thanks for any help.