Peavey Classic 30 problem child

[Ernest Ball]

I have a Love/Hate relationship with my 1994 Peavey Classic 30, and it’s mostly the latter. In an attempt to get it sounding like I think a low-powered EL84 combo should, I’ve had the following tweaks done by a full-time amp tech: simplified input stage, cathode bias mod, tone cap replacement, etc, as per 'Blue Guitar mods', and triode / pentode switch. I’ve also changed the speaker to a 16ohm Eminence Private Jack and tried various input and output valve swaps – the only ones that made an improvement to my ears were TAD EL84s, but they don’t last very long! (JJs sound bland in this amp to me). It really annoys me the way the normal channel refuses to distort / saturate in a musical way when it's turned up, and the overdrive channel only sounds ‘ok-ish’ with the volume around 3. Above that, it just gets louder and cleans up slightly, rather than sounding better (ie; there's no 'proper' power amp saturation happening in either mode). These last comments also apply to the amp when stock, so I don’t think the mods are the issue.

My other amp is a Peavey NanoValve 5 watt 1x8’’ combo, with an 8ohm Jensen MOD speaker upgrade and single TAD EL84, and this sounds really good – it distorts smoothly up to about two-thirds on the volume knob, then saturates more and more without significant volume increase when turned up full, when it sounds great. It's like a baby AC30. If I could get the Classic 30 to behave more like this, I’d be a lot closer to being happy!

I understand that the NanoValve has no negative feedback circuit, so I was wondering if it was possible to remove this from the Classic 30, and how tricky is it to do if possible. (And would it make the difference I crave?). The NanoValve is also Class A, so I wouldn’t expect the A/B Classic 30 to sound ‘exactly the same but bigger’, but I was also thinking about changing the speaker to a 12’’ Jensen MOD (as I like the voicing of the 8’’ version in the NanoValve and I’ve read lots of good reviews of this speaker as being a good swap in ‘problem amps’), BUT the 8ohm version, running off the extension out socket, with the internal speaker terminals safely taped up.

I don’t really want to go to the hassle of changing the Classic 30 or relying on pedals to get my basic sound, as ‘on a good day’, the sound is a fairly close to the tone in my head, but it still needs some work, so any thoughts and advice appreciated.

Thanks.

[km6xz]

You have made so many changes that it is unlikely to get the results you seek without doing a complete analysis of what you have now. That is not a very effective way to get to a specific goal. You need to identify what characteristics you seek in technical terms, not just to sound better to your ears. Throwing mods at it randomly is about as effective as throwing words at a blackboard and expecting to eventually get a great novel.
The little amp will have much different character since it is a Class A without feedback which will distort at different levels with different frequency content than a Class AB push-pull amp. You might be better off starting with an amp you think is 95% of the way to what you want than paying a tech to experiment. That way the last 5% can be defined in terms of an already good sounding amp.
The references to knob position makes no sense to anyone other than yourself since only you know the output level of your guitar. The gain settings are that, the amplification factor, not the volume. Volume or power depends on signal to which the amplification factor it applied. If your guitar has high output, even "3" might be overdriving the power output stage but a low output guitar might require a "8" setting to achieve the same volume. Knowing just the dial numbers does not shed any light on the performance of the amp

[Enzo]

What he said^^^^


But if you are doing to do one more mod to this thing, you can open the NFB loop by lifting C36. Or the jumper from it to the tube board.