The 2nd one is an original ST-70 with the original driver board replaced with a Chinese re-pop of the original (still driving 7199's), a Dynakitparts replacement power capacitor and a Dynakitparts bias kit. installed. It's paired PAS is a PAS-2 with chinese re-pop's of the original boards installed (this whole rig was an experiment with the Chinese boards, and to be honest, I'm quite pleased with how they all sound). Since the PAS-2 cosmetics were awful, I topped the rebuild off with a black anodized front panel and repaint of the case .
Anyway, on to my SCA-35 questions / comments. Both of the above systems have been used in the past with my Boston Acoustics A60's at one time or another. Not the greatest speaker, but a good solid bookshelf. When driving them with either the ST-70's sound level was quite good, never needing more than 1/3 deflection of volume on the PAS to get them to a comfortably loud level.
This brings me to the SCA-35. I recently acquired a factory wired SCA-35. It was sold working, and looking inside prior to power-up, nothing outstanding looked to prevent giving the unit a test run. Tubes installed were JJ EL-84's, Dynaco Branded 7199's and dynaco branded 12AX7's on the preamp board.
So, I threw caution to the wind, hooked the SCA up to the BA's and connected my iPhone via the 'Spare' input to the amp. Power up was uneventful (as in no smoke leaked out, and no strange sounds). Sound is clean, though not as 'transparent' as either of my PAS / ST-70 combos. My biggest concern and question is sound level. In order to get what I would consider a nice sound level, I had to max out the volume control. So.....
1 - yes I realize the SCA-35 is rated at 1/2 the power of the ST-70, and I have no idea how the internal preamp gain compares to the gain of a PAS, but would the sound level really be that much lower?
2 - if no to 1, then where to start looking? (I have no way of checking the 7199's, but do have a good set on the shelf from the ST-70 that was converted to a VTA-70 to try)
3 - Seeing as this thing is all original, what upgrades should be considered, or is there more value in conserving it as a factory example? My thoughts are to go with Dave's SCA-35 power supply board, and perhaps his amplifier (PC-10A) boards or a set of Chinese re-pops. Or, should I conserve the original and just replace the can capacitor? (I assuming that cap is original and hence a ticking time bomb)
In some respects wish I had gotten one in worse shape, then there would be no question on whether to update or not. Don't want to lower the value of the unit should I decide not to keep it.
The group collective thought is appreciated.