I have revived a 6336A push-pull experiment that I tried late in 2019, based loosely on Lynn Olson's "Amity". It is a transformer-coupled amplifier without global or local negative feedback. The attached schematic shows the toplogy (there have been some minor changes to resistor values) .
I designed it to work into a 4 Ohm load and it delivers 1W<0.1%THD, 13W@1%THD and 20W@5%THD. The distortion is 3rd harmonic only, with some 5th harmonic emerging at 20W and 5%THD. No even order harmonics are evident anywhere, demonstrating effective push-pull distortion cancellation. The -3dB bandwidth is 12Hz to >45kHz @1W, 19Hz to >45kHz @13W.
The ugly but functional steel chassis is a recycled 1980s ferro-resonant power supply conditioner once employed to protect mainframe computers at the university down the road. One night it gave its life saving the computers from lightning strikes - as a somewhat underdone Dr Frankenstein, I have reanimated it using only mains electricity ... 🙂
I designed it to work into a 4 Ohm load and it delivers 1W<0.1%THD, 13W@1%THD and 20W@5%THD. The distortion is 3rd harmonic only, with some 5th harmonic emerging at 20W and 5%THD. No even order harmonics are evident anywhere, demonstrating effective push-pull distortion cancellation. The -3dB bandwidth is 12Hz to >45kHz @1W, 19Hz to >45kHz @13W.
The ugly but functional steel chassis is a recycled 1980s ferro-resonant power supply conditioner once employed to protect mainframe computers at the university down the road. One night it gave its life saving the computers from lightning strikes - as a somewhat underdone Dr Frankenstein, I have reanimated it using only mains electricity ... 🙂
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6336A is 6080 on steroids. All 6080 circuits can be adapted to 6336A, just need a beefier power supply.
6336, No Problem to drive using a bootstrapped driver stage, just as McIntosh & Electrovoice do. I’m puzzled why more people don’t do this instead of constructing brute force drivers. I built this project as a ‘Proof of Concept’ about 25 yrs ago. On a 400V lab supply a PP pair of 6080s is good for an easy 25W. The front end is a 2-stage differential amp consisting of 6SL7 & 6SN7. The bootstrapping is obtained from the UL taps on the OPT.👍
An article describing this project was published in Glass Audio, Feb 1999. And a follow on article a month later describing the bootstrapping accomplished without the need of UL taps on the OPT. There was also a short description of the circuit using the UL tapped OPT in Electronics World, July 1998.😀
The major problem I see with the 6336 is the 5A heater current. Finding sockets that will handle that for the long term might be a problem. I wonder what the ancients used when they built their Regulated PS’s. 👎
An article describing this project was published in Glass Audio, Feb 1999. And a follow on article a month later describing the bootstrapping accomplished without the need of UL taps on the OPT. There was also a short description of the circuit using the UL tapped OPT in Electronics World, July 1998.😀
The major problem I see with the 6336 is the 5A heater current. Finding sockets that will handle that for the long term might be a problem. I wonder what the ancients used when they built their Regulated PS’s. 👎
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