RMC - RMC1 Wah (Geoffrey Teese)

analogguru · Post by **analogguru** » 14 Sep 2007, 12:14

Here are some guts:

http://www.foxroxelectronics.com/Wah%20 ... 0RMC1.html

analogguru

JHS · Post by **JHS** » 14 Sep 2007, 15:40

Who needs it?

The only interesting things for me on his site are the Rocker and the Fillmore Wah (if they don't have this useless crap in it like the RMC-Wahs).

JHS

MoreCowbell · Post by **MoreCowbell** » 14 Sep 2007, 18:28

JHS wrote:Who needs it?

The only interesting things for me ....

Thats a fairly self centered statement. Just because YOU aren't interested doesn't mean somebody else isn't.

I'm not really into wahs, but AG making the effort to take and post gut shots is appreciated.

Bernardduur · Post by **Bernardduur** » 27 Mar 2010, 21:03

Schematic of a RMC RMC1C wah I had on my bench : see here

All resistors are metal film expect for the CC which are carbon comp. 220n caps are MKT, others are MF. Transistors are metal cans with no markings.

devastator · Post by **devastator** » 27 Mar 2010, 21:22

thanks !

CHEEZOR · Post by **CHEEZOR** » 28 Mar 2010, 00:20

Very cool. Thanks everyone!

JimiB · Post by **JimiB** » 28 Mar 2010, 03:26

What its not a digital delay being marketed as an analog with tap tempo?

The RMC1 I had in my hands recently had a BC108B and a BC108C in it.

RnFR · Post by **RnFR** » 28 Mar 2010, 03:32

Bernardduur wrote:Schematic of a RMC RMC1C wah I had on my bench!

All resistors are metal film expect for the CC which are carbon comp. 220n caps are MKT, others are MF. Transistors are metal cans with no markings.

nice one!

soulsonic · Post by **soulsonic** » 28 Mar 2010, 03:52

I think there might be a mistake in the schematic. Shouldn't the output connect to the "hot" lug of P1, not the wiper?

Thanks for tracing!

Bernardduur · Post by **Bernardduur** » 28 Mar 2010, 08:27

Woops...... shouldn't make schematics late at night

New schematic

jt · Post by jt » 28 Mar 2010, 09:35

Thanks Bernardduur

R.G. · Post by **R.G.** » 28 Mar 2010, 15:20

I think there's another mistake or two.

As shown, I think the 10uF C3 would eat all the signal from the feedback path of the first transistor and kill any wah effect. I think the connections of L1, R6, R7, R8, C3 and C4 are a bit scrambled.

ryanuk · Post by **ryanuk** » 29 Mar 2010, 10:55

R.G. wrote:I think there's another mistake or two.

As shown, I think the 10uF C3 would eat all the signal from the feedback path of the first transistor and kill any wah effect. I think the connections of L1, R6, R7, R8, C3 and C4 are a bit scrambled.

Agreed - the error is the R7 connection.

R7 should be disconnected from R5/L1/R6/C3/R8 and then connected to the junction of R6/L1/C4

Check out this link...

http://www.effector-repair.com/index.ph ... _WizardWah

I realise this is for the Wizard Wah and so values may differ, however, the outline anatomy and layout should be the same. I've been meaning to draw up a schem from the pics on this page for ages. (I think Bajaman beat me to it with this Baja Wizard Wah Wah photo essay).

RyUK

Bernardduur · Post by **Bernardduur** » 29 Mar 2010, 18:16

Woops; completely true! I REALLY should try my tracing when I am not in a hurry

Ed G. · Post by **Ed G.** » 02 Apr 2010, 03:02

Ok, so what's the deal with the 10pf caps? Looks like some local feedback to reduce high end? Personally, I can't get ENOUGH high end out of a wah. I don't go full toe-down that often, but when I do, I want to inflict PAIN on the audience.

phibes · Post by **phibes** » 02 Apr 2010, 04:24

Help stop radio interference.

Ed G. · Post by **Ed G.** » 02 Apr 2010, 19:11

Seems like radio interference is most likely to come through the inductor. Why not cover the inductor with a shield of some sort and ground it?

analogguru · Post by **analogguru** » 02 Apr 2010, 19:37

Ed G. wrote:Seems like radio interference is most likely to come through the inductor. Why not cover the inductor with a shield of some sort and ground it?

This could be true with a plastic case. But a serious wah is in a metal case which shields the inductor from RF itself. The RF induced comes via the cable and therefore the ampification at radio-frequencies is reduced with such a capacitor.

Here are some tips against RF from the Audio Handbook by Dennis Bohn:

AUDIO RECTIFICATION
Or, "How Come My Phono Detects AM ?"
......
Audio Rectification Elimination Tips:

- Reduce Input impedance.

- Place capacitor to ground close to the input pin or base (~ 10 -300p).

- Use ceramic capacitors.

- Put ferrite bead on input lead close to the device input.

- Use RF choke in series with input (~ 10µH).

- Use RF choke (or ferrite bead) and capacitor to ground.

- Pray.

In the picture below you can see that some people already tried to screen the inductor. They used conductive silver, but I think with restricted success.

analogguru