In my many years of working with and demoing amplifiers I’ve picked up a few tricks for optimizing the performance of tube guitar amps. One common sense trick that never ceases to amaze those I’ve shown it to is how to adjust the gain and equalizer structure on a tube amplifier in a way that optimizes touch sensitivity and allows the notes to bloom. The better the amplifier, the better it works.
So here’s what I do:
1. Turn the amp on with nothing plugged into the input
2. Turn the master volume (if applicable) and input gain all the way up so you can hear the idle noise floor of the amplifier
3. Turn the bass, middle, treble, and cut/presence, reverb (if applicable) knobs all the way down
4. Starting with the bass, slowly turn it up until you hear it ‘kick in’. You will hear a noticeable jump in frequency where you’ll detect an audible fullness that resembles a low frequency hum. Be careful to place the potentiometer right on that point.
5. Do the same thing with the middle, treble, and cut/presence knobs (in that order). Each one will have a point where there is a noticeable shift in frequency. That’s where the threshold lies. Set each knob precisely on that point.
6. Turn down the input gain and then slowly bring it up until you hear it ‘kick in’ (there will generally be two places on the dial where a drastic increase is heard. Select the first one for edge of break up and the second one for higher gain).
7. Do the same thing with the master volume. I recommend running the master wide open, but that’s not always feasible in a live scenario.
7. Plug in your guitar, strum a chord softly, then hit it hard.
You are going to notice a couple of things that occur by setting every knob on your amplifier right on their threshold. Firstly, the dynamic response will become much more touch sensitive as softer attack stays below the overdrive threshold and more aggressive playing pushes through and beyond it. Then you will notice that single notes tend to bloom more easily and big chords respond with a k-r-r-r ang! Again, this has to do with that threshold response. When the note or chord is first struck the amp compresses, releases the sound above the threshold, and then slowly becomes clearer as it descends back through the threshold and naturally fades out.
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