guitarify ampeg bass head?

[cheeseface]

I've aquired an ampeg b25 bass head for cheap and it works nicely. I play guitar through it with a 4x12 guitar speaker cab.
If possible, I'd like to have it modified to suite my needs. The sound is somewhat "stiff, constipated, clogged, stuffy" for guitar. It also lacks top end sparkley chimeyness.
I know the tone stack can be replaced for one thing. I wonder if somthing can be done to cause more ditortion in the output tubes [7027a x2], as this amp was designed to remain clean even at high volume. An ampeg thing you know eh? getting a little sag out of it may be nice too. [5ar4 tube rectifier]
So far I have very little invested in this amp so I'm happy to mess around with it if my desires are feasable. or perhaps I'm being nutty an should just get a guitar head.
What do you think?

 

[glassman]

Re: guitarify ampeg bass head?

This amp has a lot of headroom, primarily due to its high plate voltages (500 v) and also due to the gain structure of the preamp/phase inverter. It would not be economical to raise the gain in this amp. It would be best to set it up for a sweeter clean tone and drive it with outboard effects. The good news is that with all the headroom this amp has, it also has the bandwidth capability that comes with that. I wouldn't mess with the tone stack either. It is a high loss design but that also adds to the adjustability; not to mention that the Ampeg design would require you to change all the components in the tone circuit. The 7199 two stage phase inverter doesn't respond well to being overdriven.

I would start by removing the 50 pF cap that bypasses the 56K resistor in the feedback circuit (C21); that will give it some sparkle.