Bandmaster conversion

[Smokebreak]

I've got a Bandmaster here that I just starting converting. Normal channel stays the same, trem circuitry comes out, and vibrato channel becomes 2nd/3rd gen style, straight OD. That way, user can plug into both channels, and A/B.
This means I'll have to use mixers to join the channels before the PI.
I really like the 180K to ground, then 1M to Master feel/tone in the original amps, though I understand this was basically to match up volumes of OD and clean, before the ratio came about.
Well, if I use that network, and mix channels with say 220Ks, then I'll lose a lot of signal in the OD channel of this conversion.
I'm interested in keeping the response and attenuation the same for the OD. I'll no doubt fiddle with this until it sounds good, but how would I go about calculating this, at least for a more accurate starting point?

[hitchcaster]

do a ultraphonix and go/mod from there maybe

[Smokebreak]

What is this ultraphonix you speak of? Never heard of it .

[Smokebreak]

Kidding aside, the closest I've come to the drive sound of Mr. Fuchs playing that UP Showman in the hotel room is Merlin's medium gain preamp, with selected tone stack and power section. Both are wonderful sounding amps.

However, that's not my concern here, as I ran the customer through a bevy of amps, and my outlined topology is what he wants.

I figure I'm about halfway through. I'm trying to make great care to use what was already there. While my goal is to make an awesome sounding amp, I'm struck by the reverence to be able to put put this thing back to stock, if need be at some point.

It looks like the only real modification done before I got it, was changing the normal channel .1 tone cap to .022. I'm gonna leave alone things like that, and drifting plate resistors, till fire-up. That unshielded, non-gridstopped OD1 is just a placemarker, unless maybe we don't need shielded wire everywhere, but I think we do, as well as treble bleeds.

[Structo]

Looks like a fun project.

In my own limited experience, I find that the farther I strayed from Dumble topology the less it sounded like a Dumble.

Of course there are no rules unless you are looking for a dead on clone.

Or you want it to sound like a Fuchs.

Basically, Fender blackface cleans and that great overdrive tone.

[Smokebreak]

Big time fun over here Tom!

I'm sticking with basic Dumble topology, but it's not a clone. I'm basically trying to clone one of my own amps that the customer played through, and wants that tone in the Bandmaster. The replacement OT that he bought for this just happens to be the same OT as in my amp, and voltages should come out very similar, so we'll see...
You nailed it - BF cleans and killer OD
In regards to my first question, concerning compensating for the fact that I'll be mixing the BF cleans with the straight OD channel, I figure I'll start by changing the 180K to 1M, and the 10n to 2n, to keep the response the same, then mix with 220Ks into the PI. We'll see what that gets me.

[Smokebreak]

This one came out very nice, and it's now out the door
I spent a couple hours with the dude and finished voicing it while he played, to his ear. Even as mainly a strat player, he settled on 1u cathode for CL1, 4u7 CL2, 2u2 OD1, 4u7 OD2 and 330p snub for OD1, and 1n for OD2!...across the plates. He liked the 500K/.002 treble bleed range.

As for mixing the normal channel with the now straight OD vibrato channel, I settled on removing the 180K to ground(and replacing it with nothing) after OD2 10n coupler, and then 470K, instead of 1M, to the MV. This worked very well, as I could lift the 220K mixer from the "clean" channel, listen, and then try and duplicate what I heard, with it mixed.

With the added filter stage, I was planning on having to move some grounds around, but this thing barely hissed, much less hummed. Kudos, Leo.