REEVES ELECTRO: ZO

I saw this on the Gray Bench Electronics youtube channel, and given the cost and apparent popularity of Reeves pedals, I thought I'd post a layout.   The schematic is also on screen for a lengthly period of time. 

In depth explanation provided at Gray Bench, but in short, it's a silicon two transistor Zonk II with mods. There were multiple versions of the Zonk II back in the sixties, with distinctly different circuits - just scroll through the page on fuzzboxes.org to see what I mean. 

 

REEVES ELECTRO ZO  -  VERO LAYOUT

I added a polarity protection diode to the circuit, cause why not when there's room.    

updated v1b - pot value corrected, see comment section

ZO NOTES

You can read the notes on the schematic in the video, but here's a short list

• the 10k bias pot is sometimes replaced with a fixed resistor
• the 470pf cap is not always present
• and read the rest on youtube... 

Or if you're really brave, instead of the using vero, follow along the instructions to build the full point to point version in the enclosure.  Hope you have plenty of blue tack and coffee at the ready.

ZO x ZONK II

Just a quick reference to the schematics - the Reeves schem is redrawn from the Gray Bench video & the silicon Zonk II is from all the usual places - but with the addition of the pulldown resistor that's visible in vintage units, but missing from a lot of schematics.

As you can see, they share the same bones, but with a few key differences.  Notice the output cap differences - the Zo rolls off a bit more bass than the Zonk, and with the 470pf cap, a bit of treble goes missing too (apparently not all Zos have this cap).

They both should have a decent amount of output, bit the Zo should have more than the Zonk by a fair margin.

Spice did not have the right silicon transistors, so I just used the plain old 2N390X in each one for a fair comparison between an NPN & PNP circuit.