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Hi I wonder if anyone can help me. I recently converted an old audio amp into a 5E3 deluxe. It sounded great at home but I used it in a band situation for the first time tonight. I plugged into the instrument high gain channel and discovered that when the volume pot is turned up from zero to about 4 on the dial the sound jumps to very loud very quickly and then backs off again as you go up to about 5. The other issue is that when I turned the amp up to full volume or near full volume the sound becomes very odd. It doesn't sound any louder than when the amp is at 3 on the dial just way more distorted. But the distortion isn't nice sounding distortion. When I hit a chord the sound seems to die and then the sound fluctuates up and down with a weird flabby, farty sound that makes it sound like the speaker is dying! Can the transformer not cope with the volume perhaps? I tried it with an extension cab and it does the same thing. I also tried in the low gain channel and both mic channels and got the same thing. The amp sounds wonderful up to about 4 on the dial where it is just starting to break up. I put a Boss SD1 in front and got a good sound but I wanted to get a good overdrive sound without the aid of a pedal. The only way I can get it to overdrive more naturally and loudly is by putting my Seymour Duncan Pickup booster in front of the amp. This can't be normal for this circuit can it? Or are they not designed to be run to max? Also the pots are making a scratching sound even though they are new and have been tested.
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Scratchy pots indicates that there's dc where it shouldn't be around them, so you need to investigate that, as the tubes might not be at the correct operating point.
Have you heard another 5E3, as the distrotion you described is within it's characteristic, best to back the vol controls off a bit. Look up blocking distortion on aikenamps.com.
PeterMy band:- http://www.youtube.com/user/RedwingBand -
Grid Stopper
Somone has suggested to me about using a 'Grid Stopper' to block distortion. Can anyone explain to me how this is done?Comment
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The input tube (68K V1 pins 2 & 7) and the power tubes (1.5K at pin 5) already have grid stoppers if you have copied the 5E3 circuit exactly. As Peter says, are you utterly sure that your amp doesn't sound "ball park" for a 5E3?
The fast ramp up on the pots is normal.
What voltages, tubes rectifier do you have? Do you have a photo of the chassis, this circuit can be fussy with regard to layout? A stiffer rectifier than a 5Y3 (like a 5V4) is usually a good bet for playing a 5E3 out with a band.
Lift the ends of the coupling caps at V1, farthest from pins 1 & 6 (plates) of your 12AX7/12AY7. Make sure that the free ends of the caps can't short against anything and connect a voltmeter from the free ends of the caps to ground and measure the dc voltage leaking accross the cap...if you have more than 0.25vdc replace the caps. As you have scratchy pots anyway you might prefer to go straight ahead and replace the caps to eliminate them. Cure this before "fixing" anything else, it's not normal.Comment
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I'm really sure that the amp doesn't sound right - it sounds completely unmusical with dips and swells - the voltage sounds like it's dropping off, the speaker thumps etc. I know Deluxes are meant to have mean distortion when pushed but this just sounds awful! I do have photos, I will attach them. I am using an old NOS 5Y3 rectifier.
Originally posted by MWJB View PostComment
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Pics attachedComment
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Rectifier?
The amp was fine first thing today but after half an hour of playing near top volume the strange odd distortion and dips and swells in the sound started again. I've changed all the tubes now apart form the rectifier. Could the rectifier be causing this problem when it gets hot? I am using an old 1950's 5y3gt made by GE. I don't have another one to try, I only have an old GE 5u4 or a GZ34. Can any of these be used to test?Comment
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