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I hope someone can shed some light on my Classic 30 problem before I throw it out of an upstairs window, then reverse my car over it. Several times...
It's a 1994 model and hasn’t been thrashed or abused in any way. I'd never had any electronic mods done until a few months ago, and after much research changed the speaker to an Eminence Private Jack - which made a big improvement. It was surely a coincidence (and / or the fact that the speaker upgrade was making me use the amp a lot more), but there was a noticeable burning smell one day. I switched it off at once and booked it in to my local Peavey repairs dept. They tested it and found nothing amiss other than a corroded extension speaker jack, which they replaced. I'd heard differing views on how soon filter caps should be replaced (anything from as soon as 3 years), so in view of its age, I asked them to do the work. Afterwards, it still didn't sound right to me, so recently I got an independent amp tech to check it out, and make some of the popular mods (cathode bias, simplified input stage and tone stack cap changes, plus pentode / triode switch).
With a fairly fresh set of TAD EL84s in, it then sounded FANTASTIC - the tones in clean or overdriven mode were so inspiring that I was playing until my fingers were VERY sore. Which is how it should be, I think! It was a real 'golden' sound - a cross between a cranked Fender Deluxe and Vox AC30, with a hint of 'proper' non-master volume Marshall. And it sounded great with any guitar. Oh Joy.
But after a few days, the magic started to drift away, and the key indicators / symptoms of something amiss are:
- Clean mode; what was a 'room-filling' volume as low as number 2 is now 4 to 5, and there's no sparkle, richness or warmth to the sound,
- Overdriven mode; comments as above, and no combination of pre and post control settings gives a natural, smooth lead tone - it’s always unpleasantly ‘grainy’ and cold - like an old-style transistor amp,
- both modes; the treble and middle pots have to be wound down so low (to reduce the harshness) that the tone is so muddy as to be unusable - even with humbuckers,
- most significantly perhaps(?), the normally excessive (by popular opinion) volume / tone 'bump' with the boost button in is now very subtle - whereas before, it was very noticeable, and an extreme increase at mid to high volume levels - as many people have commented.
Overall, it now just sounds cold, flat, dull and lifeless. I've tried numerous pre and power tube output swaps - with no joy (when it was working well, the difference between JJ and TAD EL84s was marked - with the TADs sounding much warmer and slightly louder), and any change in pre-amp sets makes no difference - apart from using 5751 / 12AT7 in various positions - when it’s the same sound, just a little quieter!).
I'm not an electronics person, so I can only guess at what the problem could be, but to my ears, it SOUNDS as though the amp is either trying to operate on a reduced domestic supply voltage (which I know is ok) or there's a voltage supply issue inside the amp - as though the tubes (esp. the output quad) aren't 'cooking' properly, and are just ‘idling’, rather than working hard. This theory could be in line with my reduced volume comment in clean mode. My tech put a bias voltage test jack on the chassis, and that's reading ok, at 30 to 32ma per tube - maybe the output transformer is faulty, and and not hitting the speaker with the right voltage? Does anyone out there have any idea what could be wrong?
My poor amp tech was very stressed at having to open the worlds’ most difficult to work on amp up for a second time (to do the cap mods), and I was hoping that I could at least give him some informed pointers when he has it back for a third time!
Hope someone can give me a clue as to what the problem is,
Thanks in anticipation!
It's a 1994 model and hasn’t been thrashed or abused in any way. I'd never had any electronic mods done until a few months ago, and after much research changed the speaker to an Eminence Private Jack - which made a big improvement. It was surely a coincidence (and / or the fact that the speaker upgrade was making me use the amp a lot more), but there was a noticeable burning smell one day. I switched it off at once and booked it in to my local Peavey repairs dept. They tested it and found nothing amiss other than a corroded extension speaker jack, which they replaced. I'd heard differing views on how soon filter caps should be replaced (anything from as soon as 3 years), so in view of its age, I asked them to do the work. Afterwards, it still didn't sound right to me, so recently I got an independent amp tech to check it out, and make some of the popular mods (cathode bias, simplified input stage and tone stack cap changes, plus pentode / triode switch).
With a fairly fresh set of TAD EL84s in, it then sounded FANTASTIC - the tones in clean or overdriven mode were so inspiring that I was playing until my fingers were VERY sore. Which is how it should be, I think! It was a real 'golden' sound - a cross between a cranked Fender Deluxe and Vox AC30, with a hint of 'proper' non-master volume Marshall. And it sounded great with any guitar. Oh Joy.
But after a few days, the magic started to drift away, and the key indicators / symptoms of something amiss are:
- Clean mode; what was a 'room-filling' volume as low as number 2 is now 4 to 5, and there's no sparkle, richness or warmth to the sound,
- Overdriven mode; comments as above, and no combination of pre and post control settings gives a natural, smooth lead tone - it’s always unpleasantly ‘grainy’ and cold - like an old-style transistor amp,
- both modes; the treble and middle pots have to be wound down so low (to reduce the harshness) that the tone is so muddy as to be unusable - even with humbuckers,
- most significantly perhaps(?), the normally excessive (by popular opinion) volume / tone 'bump' with the boost button in is now very subtle - whereas before, it was very noticeable, and an extreme increase at mid to high volume levels - as many people have commented.
Overall, it now just sounds cold, flat, dull and lifeless. I've tried numerous pre and power tube output swaps - with no joy (when it was working well, the difference between JJ and TAD EL84s was marked - with the TADs sounding much warmer and slightly louder), and any change in pre-amp sets makes no difference - apart from using 5751 / 12AT7 in various positions - when it’s the same sound, just a little quieter!).
I'm not an electronics person, so I can only guess at what the problem could be, but to my ears, it SOUNDS as though the amp is either trying to operate on a reduced domestic supply voltage (which I know is ok) or there's a voltage supply issue inside the amp - as though the tubes (esp. the output quad) aren't 'cooking' properly, and are just ‘idling’, rather than working hard. This theory could be in line with my reduced volume comment in clean mode. My tech put a bias voltage test jack on the chassis, and that's reading ok, at 30 to 32ma per tube - maybe the output transformer is faulty, and and not hitting the speaker with the right voltage? Does anyone out there have any idea what could be wrong?
My poor amp tech was very stressed at having to open the worlds’ most difficult to work on amp up for a second time (to do the cap mods), and I was hoping that I could at least give him some informed pointers when he has it back for a third time!
Hope someone can give me a clue as to what the problem is,
Thanks in anticipation!
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