• 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.

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JANE.....I'm a bit late replying.....I was thinking about the look of that square wave ...it's got ripple on it or is that due to scope sampling ?
You are using a single end amp design, I got the same square wave ripple on my push pull amp. We have one thing in common, that is we are both using a Sowter transformer. Have you tried an R/C snubber from anode to B+ on both stages ? Or did you leave it as it was ?

richj
 
richwalters said:
JANE.....I'm a bit late replying.....I was thinking about the look of that square wave ...it's got ripple on it or is that due to scope sampling ?
You are using a single end amp design, I got the same square wave ripple on my push pull amp. We have one thing in common, that is we are both using a Sowter transformer. Have you tried an R/C snubber from anode to B+ on both stages ? Or did you leave it as it was ?

richj

I think that the tendency of ringing you might see on the scope is made by the Hashimoto OPTs. The bifilar Sowter IS-transformers have a bandwidth of 270kHz (-3dB).
Here are the square waves from the output stage compared to the driver output (remember these are 20 kHz (!) ).

Output of driver stage (actually 25kHz):
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Finale output (20kHz):
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Jan E Veiset
 
first amp Je labs 2A3dx

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Thank you FastEddy it sounds really sweet if thats the right word the EH 2A3's are surpising good for the money still a bit chicken to put the rca 2A3's in yet.It took me 2yrs to make as the components are quite expensive wages being what they are but it was well worth it , I am very happy with it could never go back to solid state . For a first project the the design from JE labs is really quite good for a beginner .
Nigel
 
6F8G preamp with 6EM7 voltage regulator:

On the work bench:
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Together with some friends in the living room:
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Schematic:
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Jan E Veiset