• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

OddWatt PP UL amplifier from scratch

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Hi everybody,

here is my latest build of my premium amplifier, the OddWatt from Bruce Heran. Thank you Bruce for making this possible for all of us.

This amplifier is now second edition, it has some minor changes in the output stage wich will cause it to overdrive much more gracefully than the first version and the PSU is stabilized now. It is absolute noise free and frequency response is flat from 10 HZ till 22KHZ. Bruce rates this amplifier at 25 watt per channel, but this is with very low distortion, you get more like 33 to 35 watt per channel, before distortion becomes audible. I had the chance to compare this amplifier with some rather expensive tube amplifiers, but mine always wins, even against the Audionote. I am very proud to own such an amplifier. Here are some pics.


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Hi Ian and everybody.

Yes, I make the PC boards myself, I try to combine the best of both, the PSU on a PC board keeps everything nice together and it is safe, IMHO. The amplifier part is wired in silver vintage cloth wire, a bit a hassle to work with but the result is very presentable, IMHO. Yes, I have been planning this rebuild for some time now, it turned out the way I wanted it to, without doubt. Everybody loves the sound of this amp, but some people judge me for using solid state in my amps. Yes, there are 5 controllers in my amp, two LM317 for the constant current source and two LR8 high voltage controllers for the PSU and a 12 volt controller for the pre stage filaments. But those controllers make this amplifier what it is, the LM317 forces the amp to operate to 100 % Class A, the LR8 make out of the PSU a big battery, absolute ripple free, well as far as I can measure, and this is about -90 dB, more will my old Oscilloscope not do, but this is still better than most premium ss amps on the market. The final hum test is done with high sensitive headphones, 4000 ohm impedance, the kind of headphones you use to build a crystal radio, you can listen to your local AM station just with those headphones and 20 yards of wire and a germanium diode, pretty cool. Anyway, direct connected to the cartridge of the record player, you hear the music loud and clear, now this impressed the hell out of me.:) Anyway, why I tell you is, those are super sensitive, and if I hear no noise using those in combination with load resistors, I consider the amp noise free. Those headphones don't replace an oscilloscope, but they are a nice addition to it. If you love tubes like I do, get such a pair, if you have a chance, you can thank me later:). Tracing signal and noise, unbeatable, IMHO.


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