So my complaint with my JCA50 head has been the drive channel. The amount of gain is just ridiculous, and I don't think there's any way I could find a way to make it musical, even dialed down to 1 or 2. So I decided I'd try to put a lower-gain tube in the cold-clipping stage, thinking that it would lower the gain of the drive channel while leaving the crunch channel the same as it is now, which is definitely high gain for a clean channel. The crunch channel is reminiscent of a JCM800 as it stands.
So I checked an online schematic real quick and decided V3 was the cold-clipper, counted the third tube from the input, and swapped in an EHX 12AU7. I fired it up, and it had neutered the gain on both channels, and it's AWESOME. Basically, this is what I wanted when I bought the amp. The clean channel is clean, and the dirty channel is usable. I'm almost positive the real V3--please stand up--is not in the crunch channel's preamp topology at all, so either I can't read a schematic, or the third tube is not V3.
Either way, I'll take it, because this gives me a second channel, and I've got drive pedals in case I want to be stupid with it. I guess I can take a look at the board to see what's what the next time I swap and bias power tubes, but I'm usually not pleasantly surprised by my mistakes.
So I checked an online schematic real quick and decided V3 was the cold-clipper, counted the third tube from the input, and swapped in an EHX 12AU7. I fired it up, and it had neutered the gain on both channels, and it's AWESOME. Basically, this is what I wanted when I bought the amp. The clean channel is clean, and the dirty channel is usable. I'm almost positive the real V3--please stand up--is not in the crunch channel's preamp topology at all, so either I can't read a schematic, or the third tube is not V3.
Either way, I'll take it, because this gives me a second channel, and I've got drive pedals in case I want to be stupid with it. I guess I can take a look at the board to see what's what the next time I swap and bias power tubes, but I'm usually not pleasantly surprised by my mistakes.
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