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Vintage threads from the first ten years
amp output peak question
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 9/15/1997 9:38 AM |
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Steve Keay |
amp output peak question Hi all,, I guess I should know this but I've only looked at about a hand full of guitar amps on a scope so I'm not sure if this is normal but when I look at the output of this little Princeton amp I'm fooling with, I noticed the positive peak clips quite abit before the negative does. +12v peak compared to -16v peak or so. Is this normal? I've never seen an amp do this but again my experience is quite limited. My first guess is this is just due to the OT. Or is it related to the cathodyne type driver circuit??? Thanks in advance... Steve K |
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| 9/15/1997 1:11 PM |
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| J Fletcher | What happens when you switch the two output tubes around?What does the input to the power tubes look like?Check the grid voltage on the two 6V6's(DC with no signal).Arrest the usual suspects.Is the driver tube good?Sub a good one in. |
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| 9/16/1997 5:24 AM |
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| Steve Keay |
Thanks for the feedback John, I was working too late Sunday night on it and should have realized the wierd clipping is when the treble pot is cranked up. With the tone controls flat the signal looks perfect. Is the Fender type treble circuit supposed to induce wierdness into the sinewave? If so, I guess I never realized it till now. It causes what looks like crossover distortion and one peak to clip quite abit before the other. Someone please tell me if this is normal characteristics of a Fender tone circuit. For the heel of it, I tried swapping all the caps in the area and checked all resistors and voltage levels. Everything looks fine to me... And it probably is. Just trying to understand every detail. I guess I'll find out with the acid test tonight when I put it back together... Thanks again, Steve K |
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| 9/16/1997 10:13 AM |
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| J Fletcher | The frequency response of a Fender amp is flattest with the treble control turned off.When it's turned up,the output wave is distorted.I've never seen it look like crossover distortion,it usually affects the top of the waveform with some wierdness though.Probably depends on how far into clipping you go.....Jerry |
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| 9/16/1997 10:23 AM |
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| Steve Keay |
Thanks for the info Jerry,, It does change the top of the wave form which makes sence, but it also definitely adds what looks like crossover distortion. I can adjust the bias fine and the output looks completely normal and the tubes seem to be running optimally with treble flat so I guess I'll just try it before I worry about it... Thanks again,,, Steve K |
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