3001 controls

[Isaac]

I am an electronics technician, but not an electrical engineer. Can anyone explain to me how the 3001 controls work? Tone controls have always been a weakness of mine. Here's the circuit:
http://www.rickenbacker.com/pdfs/19504.pdf
R1 appears to be the volume control. Logical so far.
R2 is treble boost/cut.
R3 is bass boost/cut, but I don't see how that would work. I've been comparing it to the E.J. Smith circuit, and the Ric circuit looks as though it needs another resistor and a couple more caps, yet it seems to work.

[Dirk]

I believe boost and cut requires an active circuit, I see no battery, so it's really only cut since it's passive.
Cap only needed to be on the tone pot, but you certainly can run without it.
I've never looked inside a 3001 so I could be completely off base, or would it be off bass?

Dirk

[cjj]

This has been discussed several times before on the forum, here's one thread:
viewtopic.php?f=2&t=400327&p=683741&hil ... ls#p683692

As this thread points out, the original catalog called these "Treble boost" and "Bass boost", but without some sort of amplification they really can't "boost" the signal and would more accurately be called "cut" controls.

It's been said the bass control wasn't that effective, so I decided to run a simulation of this circuit.

***WARNING*** Techno-Nerd™ content ahead...

In the following image, you see 6 different "groups" of traces. These are 6 different settings of R2, the treble cut, from 1% in the top set to 99% in the bottom (the one with the peak around 300Hz). This control does work as a treble cut, as you can see that the upper frequency rolls off at lower frequencies for the higher settings.

The "spread" of traces is setting R3 from 1% to 99% in steps of 1%. As you can see, this doesn't really change the frequency response a lot, it mostly adjusts the level along the response curve for a given setting of R2. Anyway, it was a fun exercise doing the simulation...