Do Preamp Tubes in Guitar Amps Need to be a Matching Set?

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[tdbajus]

On the 5751 front, I also happen to have a 1965 non-reverb deluxe sitting in front of me, and I've tried a 5751 in V2. It is a bit different. I'm not sure my reaction to it was the same as yours... I didn't feel that it limited the dynamics of the amp at all-- to the contrary if anything-- but I did notice that the tone thinned and brightened up a little bit. It can create the illusion of more headroom, it certainly hits the power tubes a little differently and you can turn it up higher on the volume dial before distortion-- but with the location of the volume control in the circuit, that probably just means you have to turn the volume knob up higher to get it as-loud. In any case, it's a nice thing to try but, like you, I also went back to a regular 12AX7 in mine.

You and I must live in bizarre parallel universes. If you are Good Spock, does that make me Bad Spock?

I swapped my 5751 out for a 12AX7 last night for an hour, and found the tone to be a bit thinner, far more dynamic, and much louder.

It takes some getting used to, but I like what the 5751 does for the sound of that little amp.

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It could be differences in particular tubes, or in the 20% tolerance components in the amplifier reacting to different amounts of signal gain differently. Or we might just hear differently.

Amps, even of the same make, model, and year, are an inexact science.

For a time, I owned two blackface nonreverb deluxes, that '65 and a Jan. '67 (maybe the last one ever made). They could not have been more different. I swapped speakers, tubes, everything, and they each retained their 'other-ness.' I even measured some critical resistors and found nothing of consequence.

So god only knows.

Thanks for letting me be good Spock, though, I appreciate that.