parallel fx loop...dumbleator...anyone?

[swt]

Hi. i have some dumble clones that sounds amazing. they all have the dumbleator built inside. one of my best friends is a pro musician, one of the best in my country, and after listening to them, he wants me to build one for him. but he specifically asked for two things: parallel effects loop, and a switch for humbucker/single coils.
The switch seems easy to achieve...but if you have any ideas, you are welcome.
Do you think i can turn the dumbleator into a parallel fxs loop?. any ideas?. Thanks a lot for your help in advance!...

[Luthierwnc]

I guess that depends on what you want to parallel. If you want to run it along side the place where you would normally tie in with the D-lator tube, you can just add a mix pot for the dry and wet signal.

One possible mixing circuit is from John McIntyre's Bluesmaker. The schematic is on blueguitar.org. It has a blend pot at the first gain stage between a hot triode and a milder one. I used the same idea to dial in the gain on a '59 Bassman clone with a 12AX7 in one hole and a 12AY7 in another. Works great. There are some other cool ideas on that schematic to interest a tweaker -- like the mid-boost and switchable NFB resistor values.

Was the humbucker/single idea for the guitar or something to alter the voice of the amp?

Skip

[swt]

he just wants the loop for a lexicon reverb and a delay. but wants it in parallel to have the true sound of the equipment riding with that signal...you know that those digital reverbs mess the tone a bit. so maybe i can modify the dumbleator for this...as this type of circuit was intentionally designed for this type of amp.
the switch is because he plays a telecaster, and a hollowbody guitar...mainly jazz/fusion. so the hollowbody has a lot more volume. he likes the tone of the amp, so no voicing is gonna be change. i think i'll just use a lower resistor to ground to equal the volume drop of the single coils pickups. in amps like these, so sensitive ones...whatever you plug sounds different, so there's a volume drop when changing guitars.
Thanks for your interest!

[Luthierwnc]

I'd have to put pencil to paper but it shouldn't be that tough to put a mixer between the loop and the dry. The questions in my mind are how to keep it from loading or knocking too much signal down. In some cases, the mix pot would be like a second master volume. If you come up with a schematic, post it. I give it some thought too. Clean or overall master?

As far as different guitars, your basic Fender/Marshall two jack input has a high and low feed. One side goes through a 68k resistor and the other goes through two in parallel for 34k. The latter is pretty close to the "D" 24k resistor.

sh