Revel Overdrive - Mid Boost/Cut Mod?

[temporalhaze]

Hey all,

I recently purchased two Revel PCBs and have been awaiting the build docs as I'm sure others have. While watching some demos, both the v1 [which this PCB seems to be based off] and the v2 seem pretty similar, save for v2 having a boost/cut knob for the Mids, and switchable 9v/18v options.

With this in consideration, I would love to take the Revel and add a Mid boost/cut knob to closer mirror the v2. The possible tonal possibilities from this seem at least worth asking about. The switchable voltage seems easy enough as, if I'm understanding this properly, PedalPCB sells Charge Pump breakouts to achieve this exact thing.

Does anyone have any thoughts on where in the circuit the legs of this pot could be attached to, and the value of the pot as well? Forgive my ignorance as I'm newer to schematics beyond surface level interpretation. I'd love to use this as a chance to learn more.

PedalPCB docs for reference

Demo that demonstrates both v1 and v2 side-by-side, including the 9v/18v differences

Any input is appreciated, thanks in advance!

 

[temporalhaze]

@Robert - tagging you for your two cents if you have any thoughts. I see you're tagged as Staff/Reverse Engineering also. Low priority/whenever you have time. I'm only pushing for movement as I'm looking to make another wave of component purchasing soon. If I could include the needed parts for this mod in that wave that would be wonderful!

 

[Robert]

This is pure speculation, but...

The LCFR is based on the Xotic BB Preamp, which in turn is basically a modified Tubescreamer with an active tone stack and Tone control pot replaced with two resistors.

The Xotic BB Preamp w/ Mid Boost was the same circuit, except it also had the original tone control of the Tubescreamer (Mid Boost).


Without seeing the LCFR V2 my first guess would be that maybe they incorporated the Mid Boost control of the Xotic BB w/ Mid Boost back into the circuit.

 

[temporalhaze]

This is pure speculation, but...

The LCFR is based on the Xotic BB Preamp, which in turn is basically a modified Tubescreamer with an active tone stack and Tone control pot replaced with two resistors.

The Xotic BB Preamp w/ Mid Boost was the same circuit, except it also had the original tone control of the Tubescreamer (Mid Boost).


Without seeing the LCFR V2 my first guess would be that maybe they incorporated the Mid Boost control of the Xotic BB w/ Mid Boost back into the circuit.

I appreciate the quick insight and pointers! This is a huge help to possibly make these builds really awesome.

Using the Revel's schematic and the XB-MB schematic for reference here...if I am staring/comparing this correctly, could I add the XBMB's W20K pot in between the junction at R10, C6 and R12 and have a mid control for this circuit? Screenshot snippet attached with the respective lugs labeled on the Revel's schematic, second snippet is the XB-MB's original Mid pot placement.

 

[falkry05]

I added a A50k w/ one 18K between lugs 1&2, and an 18K between lugs 2&3 to form a poor man's A20.9K taper per temporalhaze's schematic snippets. Brings a whole new dimension to the Revel. There's a lot of change in a small range of the pot, but it definitely works. Saved the pedal from going into the disappointed pile.

 

[temporalhaze]

I added a A50k w/ one 18K between lugs 1&2, and an 18K between lugs 2&3 to form a poor man's A20.9K taper per temporalhaze's schematic snippets. Brings a whole new dimension to the Revel. There's a lot of change in a small range of the pot, but it definitely works. Saved the pedal from going into the disappointed pile.

I'm stoked to hear that it works! Per Robert's note that it's mainly modeled after an Xotic BB, I decided to go with the W20K pot. The taper on W pots is super interesting too, I'm excited to get one up and running this weekend!

I'll definitely either follow up here or make a Build Report post with my findings. Thanks for confirming my suspicions!

 

[falkry05]

One thing to note is you will want to remove R10 and R12, wiring the pot to R10.2 and R12.1 wiring identical to the XBMB.

 

[temporalhaze]

One thing to note is you will want to remove R10 and R12, wiring the pot to R10.2 and R12.1 wiring identical to the XBMB.

Ah yes that's right. Did you wind up wiring Lug 2 to the cap also?

 

[falkry05]

Correct, lug 2 goes to C6.2 as seen on the XBMB. Since both resistors are removed I connected lug 2 to R12.2.'s pad. Seeing as I already drilled my enclosure I mounted the mid pot between the bass and treble holes from the lcfr template, shifted down towards the switch a bit. The hole is close to inline with the bass/treb leads.

 

[temporalhaze]

Correct, lug 2 goes to C6.2 as seen on the XBMB. Since both resistors are removed I connected lug 2 to R12.2.'s pad. Seeing as I already drilled my enclosure I mounted the mid pot between the bass and treble holes from the lcfr template, shifted down towards the switch a bit. The hole is close to inline with the bass/treb leads.

Sick! Good thinking on lug 2 connecting to R12.2, I hadn't considered that.

I actually plan on putting my mid pot square in the middle of the four stock pots just like the original LCFR2 is, and shifting the LED down towards the foot switch.

 

[falkry05]

I already had the stock pedal built for a couple weeks, and was itching to add a mid control. Finding this thread on the same day helped things along. I ran out of knobs, more on order to fix the odd one out