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beginner forum: for novice and developing blues harp players > Fender amp low gain input vs tube swap
Fender amp low gain input vs tube swap
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26 posts
Jul 17, 2020
2:32 PM
I’ve got several BF era amps that I picked up and use as a guitarist. Now that I’m also playing harp, I see people recommend switching the 12AX7 for a 12au7 or similar to lower the gain for harp. What about just using input 2, which is already lower gain? I’ve got a VibroChamp with a nice Eminence speaker in it that should be awesome.

Last Edited by Hamerman on Jul 17, 2020 2:33 PM
6763 posts
Jul 17, 2020
4:10 PM
Sure, might be OK. Easy enough to try.

I reckon if I had a vibrochamp I would begin doing just that.

Mic choice makes a difference too.

The other thing you can try is using a volume control on the mic or, fairly common now is a pad like the Lone Wolf Mojotone or Mojotone Deluxe. I think the Memphis Mini Little Fatty is the same kind of deal.there may be others. There's also pre-amp pedals which can give similar results

I know some people who run small amps with the volume turned up high, and have a mic with volume control which they use to regulate the feedback.

All of this is about the problem caused by presenting the first pre-amp gain stage with a signal somewhat more powerful than that provided by typical guitar pickup

This is a bigger problem with some mics and amps than others.

Sometimes changing tubes doesn't yield good results. I have a hypothesis that the reason a12AU7 (for instance) might seem to kill an amps signature sound and leave it sounding dull is not just because there's not enough gain, but because the circuit is wrong for that tube and consequently is operating in a poorly balancedway.
I had this"flash"of insight late one evening when reading the valve wizard pages about pre-amp design, and is a topic I really need to look at again but in any case, whatever the reason, it's true that tube swaps sometimes just don't sound good.
Conversely, sometimes it works really well.

I think best to start with the simplest and cheapest possibility and go from there.

jbone used vibrochamp amps I think.

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