Dumbleator remote volume boost add on

[Richard1001]

I don't know if this has been done before or if anyone would like to build this, but i thought i'd share it.

I have a Ceriatone C'lator which i use live with the SSS i build a while ago. The SSS has remote PAB and mid boost and with an overdrive (TS or so) in the front is has a great lead tone. The C'lator is used to for my Roland delay in the loop.

While most of the time using the volume knob on my guitar is enough, sometimes i would like to boost my solo volume post OD (mastervolume)

My idea was to build a remote switch in the C'lator, but there is no separate winding on the transformer for relays and i wanted to add it without changing the original to much.

So i made a powersupply with coupling caps to connect it to the existing filament voltage to have ground isolation and made it silent so it doen't add hum and the DC voltage has next to no ripple. I used two transistors (BC108C) to drive the two VTL5C1 vactrols and invert the drive current so when one is on, the other is off.

To boost the output i placed the output pot between the two halfs of a stereo pot (which sets the volume boost) connected the opposite way. When the boost knob is turned up, the ground gets lifted and the resistance on the signal side is lowered. This is the same as setting the output volume pot higher.

When the boost is turned off, one vactrol pulls the output pot back to ground, while the other vactrol disconnects the wiper of the other half of the boost pot on the signal side. Essentially this is the same as turning the output pot back to the set value.

I used a 25K linear stereo pot an a 250KA output pot. The real value is 28K and 224k so the total resistance is 252 K. Because the stereo pot works in opposite way, the load the tube sees stays the same.

Here the schematic and some pictures:
(Edit: the diodes are SB160's not BS160)

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[dcribbs1412]

Ingenious design. Thanks for sharing this.

D

[Richard1001]

Thanx