Many years ago, when I had a bit more leisure time, I planned to build amps with different designs and topologies to investigate the "sound" of each.
Among them were push-pull AB designs (of course); single-ended using 6C33 pentodes, parafeed, etc. I'd read about OTL amps and their costs and reliability problems. And then I ran into a schematic for a 25 or 80 watt/channel OTL amp, called "The Transcendent OTL", in Bruce Rozenblit's interestingly titled book, "Audio Reality." The design was scalable (25 or 80 watts per channel) and used EL509 outputs.
Bruce, an apparently humble man prone to understatement, had this to say about his design:
"This is it! It doesn't get any better than this. If you want clarity, detail, resolution and accuracy, nothing beats an OTL . . . and this is the best OTL there is." Further, "It is light, airy, open, tremendously fast, yet totally musical without coloration of any kind."
How could anyone resist?
So initially, I put a lot of thought, time, and money into the project. I decided on separate power supplies, using custom-wound toroid transformers. Also, I planned to use 6CG7s for drivers instead of the tubby-sounding (IMHO) 12AU7s.
I spent a bunch of time cutting holes in one of my chassis. And then it sat on the shelf for years, as various audio projects tend to do around my house.
So now I'm back on task. I thought I'd post a thread of my progress. And I promise not to use as much understatement as Bruce.
Among them were push-pull AB designs (of course); single-ended using 6C33 pentodes, parafeed, etc. I'd read about OTL amps and their costs and reliability problems. And then I ran into a schematic for a 25 or 80 watt/channel OTL amp, called "The Transcendent OTL", in Bruce Rozenblit's interestingly titled book, "Audio Reality." The design was scalable (25 or 80 watts per channel) and used EL509 outputs.
Bruce, an apparently humble man prone to understatement, had this to say about his design:
"This is it! It doesn't get any better than this. If you want clarity, detail, resolution and accuracy, nothing beats an OTL . . . and this is the best OTL there is." Further, "It is light, airy, open, tremendously fast, yet totally musical without coloration of any kind."
How could anyone resist?
So initially, I put a lot of thought, time, and money into the project. I decided on separate power supplies, using custom-wound toroid transformers. Also, I planned to use 6CG7s for drivers instead of the tubby-sounding (IMHO) 12AU7s.
I spent a bunch of time cutting holes in one of my chassis. And then it sat on the shelf for years, as various audio projects tend to do around my house.
So now I'm back on task. I thought I'd post a thread of my progress. And I promise not to use as much understatement as Bruce.
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