Dumblish and Marshall preamp channel switching

[10thTx]

IF you were going to attempt to graft a Marshall preamp into a Dumblish clone, which relay switching style would you attempt?

I attached a SCH schematic. If someone has a better idea and would like to edit the schematic & repost, I would appreciate the help.

On the version that switches after the first triode, I put a .47 cap there prior to the dpdt relay. I used the .47 value because I wanted to minimize the loss of values with caps in series.

With respect, 10thtx

[ic-racer]

Maybe I'm missing something but I see the same relay setup in both posted schematics.

There were a few other things that caught my eye and I wanted to point them out to make sure they were not mistakes.
V2B do you really want 100k/2.2k?
The '124' tone shown is the early one, did you want that one or the 'Skyliner' ?

[10thTx]

Maybe I'm missing something but I see the same relay setup in both posted schematics.

One version switches right after the input jack.

The other version switches right after the first triode.


I'm not concerned about the component values at this juncture, just trying to get the relay switching topology figured out.

Thanks. With respect, 10thtx

[ic-racer]

Maybe I'm missing something but I see the same relay setup in both posted schematics.

One version switches right after the input jack.

The other version switches right after the first triode.


I'm not concerned about the component values at this juncture, just trying to get the relay switching topology figured out.

Thanks. With respect, 10thtx

Tank you for pointing out the obvious.
So the Marshall could have up to six preamp stages?
I have no prediction other than to try it both ways and see how it works.

[da Geezer]

I like the one that switches right after the input jack the best, as it would allow you to have more control over tweaking each preamp. I would want to be able to try "high plate" and "low plate" Dumble topologies, and to try different setups on one preamp without affecting the other.

$0.02

Geezer

[10thTx]

hey Geezer,

Your "two cents" is worth a million!

THANKS for the feedback!

Best regards and respect, 10thtx

[ic-racer]

duplicate

[10thTx]

So the Marshall could have up to six preamp stages?

I guess that would be possible? But that isn't what was I had in mine.

4 gain stages - Dumblish

3 gain stages - Marshall type

The Dumblish stages don't go into the Marshall type. They're separate.

I think 6 gain stages would probably oscillate like crazy?

with respect, 10thx

[Micky D]

I like the one right after the input jack as well. What serves as the grid leak path on V3b (hotswitch)? Cool ideas...

Cheers,

Micky D

[da Geezer]

I like the one right after the input jack as well. What serves as the grid leak path on V3b (hotswitch)? Cool ideas...

Cheers,

Micky D

I would put a pot (50k, 100k, 250k) in that spot...once again, for more control.

G

[10thTx]

I would put a pot (50k, 100k, 250k) in that spot...once again, for more control.

Yes, I agree with that! I drew the schematic in a hurry and the pot should've been on the grid side NOT plate side (as I drew it). Sorry about that.

With respect, 10thtx