New to forum - Magnatone amp mod

[jer]

First off, I'd just like to say Hi to all of you. I've been lurking these boards for a while, just soaking up knowledge and trying to learn about what makes a tube amp tick. Rather than building an amp right away, I thought it might just be easier to modify and tweak an existing amp and learn about things that way.

With that in mind, I have an old Magnatone 441 bass amp that's got a neat clean sound that would be perfect for experimentation.

Keep in mind that I'm familiar enough with electronics to not kill myself, but as far as altering/redesigning the amp's circuit for various things, I'm a bit out of my league.

Often when I see an amp mentioned, it'll be referred to as "Marshall-style" or "Vox-style". Here's my first question to all of you

In the schematic I've enclosed, would the amp's design be considered to be a "Marshall-style" or whatever? The output tubes are 7189's, which to my understanding, are a higher power/voltage version of an EL84., though EL84's are running in the amp currently. Off the top of my head, I can only remember Vox amps running EL84's.

My next question is this: the amp only has two knobs: one for volume, and one for tone. The tone just appears to roll off treble when you turn it.
I think I've figured out which part of the circuit is the tone stack, and initially, I'd like to put in pots for Low/Mid/Treble, and then perhaps even completely change to a different tone stack later on.

What type of changes would I need to make to that circuit to be able to have pots for Low/Mid/Treble? Also, would there be fairly basic things that could increase the gain the amp can produce?

From how the schematic appears to me, it looks as if the volume pot is just cutting gain from one pre-amp stage to the next. If this is indeed the case, then to me, it would seem that the output stage is pre-set to a specific volume, and that putting a master volume in there somewhere would allow the volume to be dropped while letting me drive the preamp harder. I'm not quite certain of what changes would need to be done to the amp to make this happen.

I'm hoping that you more experienced people here are able to make some suggestions for things that may sound neat, and give me opportunity to learn more about the workings of tube amps. I've got a ton of questions, but I'll leave them for now, as this wall of text is already gigantic lol

Jer

[Andy Le Blanc]

I started with old amps too .... its a process of decontruction
the 1M resistor going to ground between the pre and inverter would be a
good place to try a master.... there are plenty of one knob tone controls to
fiddle with before making holes in the chassis...
you can try swaping tube of differnt types in the pre...
a bass amp has more gain so if your messin around dont be suprised
by the distortion..... also that type of invertor sounds great up to a point
then it turn s ratty real quik..... the amp is more of a fender style...
like a princeston.... but with a lower gain tube in the inverter