Category: Filter

Bespeco Weeper

For no apparent reason, here’s a vero layout for the Bespeco Weeper wah effect. I guess you could either set this up as a “fixed-wah” box or put it in a regular wah enclosure with foot-controlled pot.

Based on a schematic by Gottfried Divos, found here.


This effect apparently also go by a few other names with some slight modifications to the part values. I’ll see if I can add some more info on that tomorrow.

Update (23.06.2013): Substitutes you can make to create other similar effects:

Colorsound Wah-Wah Zvex Ooh-Wah
R2  330K 330K
R5  180K 180K
R7 180K 180K
R9 470 jumper
R10 33K 330K
R12 same 470K
C1 missing same
C3 100n 100n
C4 2n2 2n2
C5 6n8 10n
C6 15n 15n
C8 100n 100n
C9 2n2 2n2
Q1 ? (medium gain silicon NPN) MPSA18
Wah pot same LDR

Update (02.09.2013): Verified as working, thanks to Clint C.

Update (12.09.2013): Not sure what I was getting at about a cut underneath R10. No cut necessary and layout has been updated. Thanks To Olav for spotting this 😉

Updated: 12 September, 2013 — 22:45

Request: Woody acoustic simulator

Make your guitar sound more like an acoustic. Mark Hammer’s schematic and design documentation can be found here. Apparently there are a few conditions that need to be met for this to sound good (read the info that goes with the schematic).

I’m not a big fan of effects requiring a bi-polar/non-standard power supply so I have attempted to incorporate a charge pump to obtain +9v/-9v in-circuit from a regular +9v power supply. I’m thinking this will work, but I haven’t tried it yet. If you go with the 7660 IC make sure you use one with an “S” post-fix to avoid high frequency noise.


Update (19.02.2013): Now also verified, thanks to Earplane.

Updated: 19 February, 2013 — 19:59

My take on an envelope controlled State Variable Filter

So a colleague of mine asked me if I could build him an auto-wah type effect, and specifically something that sounds similar to the MuTron III and it’s brethren. Another goal was to simplify the controls a bit by getting rid of unnecessary switches and pots.

Having just recently managed to successfully debug and build the MuTron III vero properly (with the frustration that came with it fresh in mind) I was a bit reluctant to go straight to that one. Rather I wanted to try the DOD440 circuit first. I got it working, but not in a satisfactory manner.

In the end I decided to sit down, read and understand the relevant circuit blocks in more detail and put an effect together piece by piece. R.G.Keen’s “Technology of…” article on the auto-wah was of course spot on, but I also found this article by Elliott Sound Products to be a great resource. Along with the schematics for R.G.Keen’s Neutron project and the Lovetone Meatball I ended up with a State Variable Filter I was quite happy with, getting rid of most of the controls only keeping a potmeter for “Q” and only using the band-pass output.

Next up was the envelope detection circuit which was a lot harder to get right (it’s probably still not right, mind you). Again I ended up with a derivative of several circuits, keeping pots for “sensitivity”, “attack” and “decay”. I also somehow made it work with a standard TL072 and not the LM1458 that the Meatball uses, but had little luck with any current limiting adjustments for the LEDs and nothing worked as I wanted it to. In the end I was inspired by the Tremulus Lune LFO and put in a trim pot set up as a voltage divider to control the LEDs off-ness. This actually worked surprisingly well and I was able to use all of the optocouplers I had at hand (VTL5C4s, NSL32s and two flavors of home-made ones).

My first take on a vero layout used 2n2 caps for C2 and C3 which I found a tad bit too trebly and switched them for 4n7 ones. R9 and R11 (both 220k) sets the lower limit for the filter sweep, and R10/R12 sets the upper. I tried using 330 ohm resistors for the upper limit, but that made the sweep way too high and I changed it to 10k.

I’ve now built this successfully using cheap LDRs from smallbear (the 9203 variant) and 3mm high-brightness clear red LEDs (5mm LEDs may not fit on this layout since the optocouplers are so close) and I’m very pleased with how it sounds! Tuned the trimmer to where the LEDs were just barely off with no signal.

Final build images coming as soon as I get around to boxing this…

Update (08.12.2012): Build complete and I’m pretty happy with how it came out in the end. And it quacks nicely too 🙂

It was a snug fit and I had to cut off one of the corners of the board to pull it off, which annoyed me somewhat.

Also, I’ve updated the schematic. I had left an extra trimmer in there that I never ended up using.

Update (24.01.2013): Layout rev. 1: I forgot to update C6 on the layout which should be 470n (like the schematic). Fixed now.

Updated: 24 January, 2013 — 23:39

LoFi Telephone Noise, take two

I did a layout for R.G.Keen’s LoFi Telephone Noise already, but with Mark Hammer mods and the noise part removed. I wanted to revisit the effect and keep the noise part as an option this time around.

After having built it I had problem getting any noise out of it at all and ended up tacking on a different “white noise” circuit snippet instead.

I don’t think the white noise blended with the signal sounds entirely convincing, but it’s an interesting effect none the less. And there’s a lot of noise on tap if you’d want it 😉

I was able to single out a single 2N2222A transistor for the noise source that was acting a lot noisier than the rest of the lot.

Updated: 21 December, 2012 — 22:39

Request: Lovetone Meatball

This is, I believe, basically a Mu-Tron III with lots of extras added. Probably a really cool build, but good luck with the wiring 😉 It probably pays to also keep the schematic close at hand (I based this one on a schematic found in the relevant thread over at FSB).


Update (18.12.2012): Layout has been verified as working, thanks to Roland for this!

Updated: 21 December, 2012 — 22:37

Escobedo’s Jawari

For no particular reason I just thought this one seemed interesting. Supposedly it emulates the sound of a sitar. Though I’m not expecting anything profound it’ll be fun to try it out.

I’m hoping the transformer will fit (looks like the same size as the one for the Octavia).

Update (25.05.2012): Now verified as working, thanks to zottel.

Updated: 21 December, 2012 — 22:32

Request: Variable bandpass filter

This is based on R. G. Keen’s LoFi telephone noise maker/emulator modified as a variable bandpass filter with the noise component removed (a mod suggested by M. Hammer). I updated the original schematic (by Keen) with the mods.

And I did a quick vero layout as well. I’ve already built this and it works, so this is verified.

Updated: 21 December, 2012 — 22:29
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