Hello Captain,
I too own a pair of Altec 1570b amps. I appreciate what you had to say about the technical aspects of them as I am always open for new ideas and rarely sell what I have aquired if its vintage gear. A closed mind and a "move on to something else as soon as you don't like what you hear" type personality is not at all my style. I still own gear I bought back in the seventies from my geometry teacher. I still have the Marantz model 7 he sold me in 1978 and somehow it still keeps finding its way back into my system since it sounds better than every other preamp I have tried since then, and I cannot count how many pre's that's been. Well, back to the Altecs. I bought a pair about 10 years ago with the hope they would drive my Martin Logan CLSIIz's to levels never before heard. Back then I had read an article in Vacuum Tube Valley describing what T.T. in Fla was doing to them and I made some of the mentioned modifications (all purely component changes as I wanted to keep them vintage looking) before even listening to them stock. I kept the tube B+ supplies basically stock as I felt going to diodes and the likes would be a step backward, but I did add some additional capacitance along with the 1KV stock can for the B+ as I felt that could not hurt. Along with that I also replaced the caps in the LV supply as it was noisy as hell. The main thing I did though was change the 6V6 drivers to EL34's since in his article Tom felt that was where the real major weakness was. I also replaced all the old carbon composition resistors with low tolerance metal oxide resistors since many of the original resistors had drifted as much as 50% or more in value over time. I also replaced the coupling caps with Hovlands. They work well, sound okay, but honestly, they suffered significantly from high end roll-off driving the large electrosats so I eventually moved on to something with better low Z drive capabilities. Lately though, I have been looking over at them, pondering what they would have sounded like stock. After all, I'm sure the engineers at Altec had nothing but performance and dependability in mind when they designed them. I'm not saying Tom doesn't know his sh!t, but he's one man working with what is there to work with. The Altec engineers were able to design everything as they wanted it to be, they were designers in the "golden age of hi-fi" faced with the challenge of building a product that not only would stand the test of harsh situations, but also be versatile enough to fit nearly any application, and sound like a professional product would be expected to sound like in doing all that as well. I guess, with all that being said, I would have to wonder what they sound like stock. A very close friend of mine bought a pair from T.T and they sounded quite nice driving his highly efficient dynamic speakers but eventually moved on as well. He never keeps an amp for much longer than a year or two anyway so I cannot say he was displeased with Toms re-incarnations, he just had to move on as usual. I hate to admit it, but mine are being used stacked up as an end table in my listening room. I said I never let anything go, and I still have them LOL. I even saved every part I removed from them originally.
So, I was thinking of leaving the supplies as they now are, (basically stock with updated caps) keeping the Hovlands and updated resistors in place, but going back to the 6V6's and associated resistors that were changed to use EL34's as drivers. I somehow feel the 6V6's triode drivers might sound better than the EL34's. And, what would be your thoughts on replacing the 12AX7 phase splitter with a 6DJ8 since the amps seem to have plenty of gain for hi-fi use. I've never been a big fan of the 12AX7 and the 6DJ8 would provide a lower impedance for the input of the 6SN7.
Whats your take on all this?
And by the way, what exactly of any value were those other guys trying to add to your comments, and why were thier panties in such a wad? I thought you were being very respectable in mentioning the obvious EXTREME HAZARDS of working around HV, and those guys acted like you spit in their face or something. All I can say is they must have felt as if their manhood was being threatend in a way that their mothers used to do when telling them to "zip up that jacket or you'll catch a death" LOL