How to add a depth or mix pot to The Worm (EHX).

[puretube]

for now I wonder:
- what the 'phase-caps' are in the Worm? Is it those three 10nF caps (C6, C8, C10)?

Yes.

- if so, why are they the same value, while R.G's article states they need to be different and a certain value (0.015uF, 0.22uF, and 0.0047uF)

More pronounced Phasing. (means less dispersed Vibe, as a compromise)[/quote]

- why was it so important that the coupling(?) caps (C5, C7,C9) are exactly 200nF instead of a standard 220nF? (The worm uses 2 parallel 100nF caps instead of a single 220nF cap.

The available 220nF caps @ E-H were physically too high to fit between PCB & chassis ...

[puretube]

Most users mention the lack of headroom with the old big box Worm.

Circuit was designed while using a Stratocaster ...

Putting the entire circuit in a simulator I noticed that the biasing of those transistors is 'skewed' which is causing the lack of headroom.

A long story ...
(starts with: "Reduce the powersupply from 310V to 9V and replace 4 12AX7`s with 8 BC550`s)


(Schemo: "Tube-Phaswahto.0", a predecessor/variant of the "Tube-Wahbrato").



Not to be mixed-up with the "Tube-Wahmolo":


[only 1 ever produced (besides the prototype for E-H), proudly personally handed-over to Prince himself on Dec. 28th, 1998 in Cologne, Germany].

[puretube]

In the newer XO version they solved that biasing problem like this:
(It also shows where some slightly different values were used compared to the original version, but they're not related to the biasing problem.

Both E-H versions differ from the Designer`s original(-s).
Original:
12V wallwart > 79L09 regulator. No Zenerdiode(-s) involved at all.
All Transistors: BC550B.

[puretube]

So, I turned my attention to the LF0 section.
I tried to simulate this part of the crcuit in Falstad (free online circuit simulator).
Here's a link in case someone wants to play with the LFO section: https://tinyurl.com/yfh32fan
Here's a screenshot of what the output looks like:

The original design doesn`t use D4+D5 south of the Range-pot. It uses a 1k5 resistor instead.
The original power-supply comes through a R38=47Ohm from a U2=79L09 into a C22=100uF, without a Zener-diode D2.

The first DTT* Wahbrato** version used a discrete 3-Transistor sinewave phaseshift-oscillator (+LED-driver Transistor) with dual-pot and a fast/slow switch.
It was abandoned due to its very slowish start-up @ power-cycling turn-on.



*DTT = "Discrete Transistor Technology" (as opposed to "Pure Tube Technology" ...)
** the term "Tube-Wahbrato" had been registered as a Trademark back then, by the designer.
("Worm" was the name that M. M. came up with for his E-H product).