10-21-2014, 09:05 AM
Steve;
I did use some parts from Tubes4HiFi and have bought a number of parts from them. I used their PC-6 and PC-5 replacement circuit boards with parts to rebuild my PAS-3X preamp. I like the quality of the circuit boards as the traces adhere far better than the OEM phenolic boards. I went with their re-layout of the OEM design which makes parts locations more logical and has lead spacing more appropriate for modern poly types of capacitors. Curcio, Van Alstine, DynakitParts, Tubes4HiFi and others all have some great offerings of modified circuits for improved audio and from reviews I believe they all provide some improvement over the OEM design. I have yet to try those. I am considering installing a VTA board for the ST-70 for improved sonics, but have not done that yet. The ST-70 has very pleasing sound that I have found no fault with after new parts were installed on the original PC board which was also modified to use 6GH8a tubes. I used a modified version of Van Alstine's input band-limiting filter on the ST-70. I did modify the ST-70 power supply to have more high voltage rating (around 600VDC) to give more ability for the circuit to survive overvoltage and also to increase the filtering capacity. That was done under the chassis using radial lead type electrolytics and equalizing resistors. The 4 sections of the existing can capacitor was changed such that two sections each were bridged together to filter the two lowest B+ voltages that feed the PC board.
The PAS-2 restoration could have been done neater regarding the input audio cables. I originally had it so, but it turned out the function switch I had versus the install information from another source did not jive completely and I wound up moving wires at the jackfield to correct the problems encountered. In retrospect I should have used my ohm meter to verify each connection point from the A and B signal lugs at the center to each peripheral lug of the new type switch and I could have avoided the mess I wound up with. However, the end result worked well, so I don't feel like self flagellation at this point. It works as originally designed except for more rapid volume advancement as the volume control is turned. The new switch does not provide for tape head function so that position becomes another high level input for say a CD player or another AM/SW or FM tuner. The volume control I bought from Tubes4HiFi had the loudness tap so that feature was restored to the preamp. I often listen to music at low levels to avoid interfering with TV in an adjacent room and use the loudness feature.
Joe
I did use some parts from Tubes4HiFi and have bought a number of parts from them. I used their PC-6 and PC-5 replacement circuit boards with parts to rebuild my PAS-3X preamp. I like the quality of the circuit boards as the traces adhere far better than the OEM phenolic boards. I went with their re-layout of the OEM design which makes parts locations more logical and has lead spacing more appropriate for modern poly types of capacitors. Curcio, Van Alstine, DynakitParts, Tubes4HiFi and others all have some great offerings of modified circuits for improved audio and from reviews I believe they all provide some improvement over the OEM design. I have yet to try those. I am considering installing a VTA board for the ST-70 for improved sonics, but have not done that yet. The ST-70 has very pleasing sound that I have found no fault with after new parts were installed on the original PC board which was also modified to use 6GH8a tubes. I used a modified version of Van Alstine's input band-limiting filter on the ST-70. I did modify the ST-70 power supply to have more high voltage rating (around 600VDC) to give more ability for the circuit to survive overvoltage and also to increase the filtering capacity. That was done under the chassis using radial lead type electrolytics and equalizing resistors. The 4 sections of the existing can capacitor was changed such that two sections each were bridged together to filter the two lowest B+ voltages that feed the PC board.
The PAS-2 restoration could have been done neater regarding the input audio cables. I originally had it so, but it turned out the function switch I had versus the install information from another source did not jive completely and I wound up moving wires at the jackfield to correct the problems encountered. In retrospect I should have used my ohm meter to verify each connection point from the A and B signal lugs at the center to each peripheral lug of the new type switch and I could have avoided the mess I wound up with. However, the end result worked well, so I don't feel like self flagellation at this point. It works as originally designed except for more rapid volume advancement as the volume control is turned. The new switch does not provide for tape head function so that position becomes another high level input for say a CD player or another AM/SW or FM tuner. The volume control I bought from Tubes4HiFi had the loudness tap so that feature was restored to the preamp. I often listen to music at low levels to avoid interfering with TV in an adjacent room and use the loudness feature.
Joe
