Plexi Drive / Velvet Fuzz

The Velvet Fuzz is basically a Plexi Drive with two switchable boost sections in front of it, so I built mine to work as a standalone Plexi or with either of the boost sections engaged. I made my own layout for the boosts sections and used the IVIark layout for the Plexi.

To be able to fit two boards inside a 125B box I had to go creative and mounted one of them under the lid and other under the top side of the box.

This is my layout for the Velvet boosts board.

MXR Phase 90

I built this using the layout by Harald Sabro at sabrotone.com. For it to work properly you need a matched set of JFETs, if you are in Spain like me, you can do as I did and buy a matched set from retroamplis.com. It worked right the first time and I'm loving it.

It is a tight fit for a 1590b but if you are tidy it should be no problem.

Simple CabSim

Schematic

This is a nice and simple cabinet simulator designed by Lart. You can find more information about it on diysompboxes.com. What I really like about this cirtcuit is that it only does one thing and it does it well, without external controls this is a perfect solution to drop in a preamp stompbox or a D.I. box.

Alternative transistors

I have simulated it in LTSpice with pairs of PNP / NPN from different series. In the next plot you can see the frequency response using the specified BC560C/BC550C pair, 2N5087/2N5088 and 2N3906/2N3904.

As you can see, 2N508X come pretty close to BC5X0C, with 2N390X having a smoother curve.

Veroboard layout

I have drawn a vero layout to build it, its a bit croweded but smaller than I was expecting. I recommend using a multilayer ceramic for the 1uF capacitor.

My build

This is my build, I used 470pF and 220pF in parallel beacuse I didn't have any 680pF, and 2N390X pair being the only pair I have at hand.

This sounds really well with a 1W PUNCH amp, I'll post a video when I have it boxed up.

11/09/2014 Update: I have uploaded my LTSpice file for anyone who want to try it. Right click on the link and choose "Save as": SimpleCabSim_yeraym_vulcanofx.asc

StoneGrey Distortion

Shoot the Moon Tremolo