The EctoVerb - a low-cost, Belton-brick-free lo-fi spacey reverb!

I love reverb effects, and I love building my own effects, but these two things aren't necessarily compatible as the only real option for DIY reverb, without going down the spring tank route, is the Belton (or Accutronics) brick.

They're a useful little brick, but not cheap, and instantly push your budget way up as they cost about £15. So I set about creating a reverb with multiple PT2399 chips, which apparently is all that's inside the BTDR-2H anyway.

My first design was based on two PT2399 chips set up in parallel, using an ultra basic configuration - using only LPF1 and OP2 to create a single repeat, and then a high-value resistor bridging pins 12 to 16 to induce the repeats (around 2M!) it's quick and dirty but it works!

I had 2 of these set up as below:

One with a short delay time and the other longer, with a 'balance' pot between them before ground for small adjustments. I also used a large pot (1M) with a 750K resistor instead of a 2M between pins 12 and 16 so I could dial in feedback amount.

It worked quite well, and I also used a series of jumpers (or a 3P4T switch, as above) to jumper the wet signal of chip 1 to the dry of pin 2, and vice versa, neither, or both, giving different reverb tones. 

It worked pretty well, but I struggled to hear the short delay tone when it came to the summing stage, it sounded a bit muddy, and I lost a lot of treble tone on the dry signal. So I went back to the drawing board.

Instead of running the chips in parallel, I ran the signal through the chips in series. This time I got a much better 'reverb' effect - a little delay before the effect came in which sounded much more convincing, and a more fluid, less choppy repeat sound. Very nice. Sound sample:

So as you can hear, some nice dwell (most of this clip is played with the delay mix quite low, straight into Ableton with a little saturation added) and it sounds a little bit like a spring reverb, but also strangely ghostly like an oil can delay or something. About half way into the clip I turn the mix up all the way to nearly 100% wet. It starts to oscillate a little bit and I've since increased resistance from the output of chip 1 into chip 2 to tame it a little bit.

 At some point in the late nights developing this, I used a JFET based buffer on the input with a wet blend to control wet/dry mix. The treble I lost on the input is now back and the mix works perfectly, from no reverb at 0 to complete drench at 10.

A video of it being played through an amp is here:


One thing I noticed is there's quite a lot of hiss, so that's something I'm still trying to iron out.  currently have very small capacitors across pins 15 and 16 so might tweak those for something larger. Otherwise, I'm pretty happy with it and have some boards on the way. It's a relatively low part count - around 20 capacitors and 12 resistors, one transistor and the usual 5v power management components for the PT2399s.

There are some kits available on eBay. The full build guide is available here.

EctoVerb!!!

Hyper Light 2 is ready

It's finished!

I made this handsome demonstration model and I have some more PCBs on for order. Let me know if you're interested in a fully built one.

A short demo video:

Hyper Light 2 Demonstration

Enjoy!
I noticed after uploading I mostly play this with the ring mod mix very low - I do turn it up at a few points though.

Boards are currently on their way to me and should be available soon.

Hyper Light 2: More Hyper, More Light.

Hyper Light 1 had a good response, so I've got the version 2 on its way to me!

New features:

• Modulation inputs for carrier frequency and time
• Almost no treble bleed!
• Improved feedback response (no lockup)
• Better mix knob (external this time)
• Onboard bypass indicator (I don't know about you but I think these are a godsend)
• Better solder pads (sorry the other ones were thin as a rake!)
• Optional SMD socket for the LMC567 as the DIP8 package is increasingly difficult to find

It's gonna be pretty! Oh and it's 1590BB now. It outgrew itself! If you're very clever it might go horizontally in a 1590B.

Shagpile envelope-controlled double tracking/chorus pedal

I've been designing this lately - the Shagpile - an envelope controlled double tracking/chorus pedal. Basically, instead of having an LFO control the clock speed of the second voice, it's controlled by a very wobbly envelope follower, so modulates in unpredictable ways rather than the smooth in-out of a chorus.

Two controls - flutter controls the gain of the envelope follower, taking it from barely a ripple to Clari-Not style huge wobbling. Tracking controls the delay time of the second voice, from barely-even-there to nearly a second later. When you strum chords with the tracking quite close and the flutter about halfway, it sounds a bit like a very wobbly chorus.

The single switch makes the second voice slide up in pitch or down in pitch.

Pics!

Just sent off for the second version of this in a prototype run, and they'll be for sale in the usual way and maybe even in a limited, full pedal version. Decal needs a little work, other than that I'm very happy with this oddball circuit.

No sound samples but you can hear it being played on all guitar parts in this tune:

HyperLight schematic

Sold a few kits now, time to post the schematic!  There's also a full build doc with BOM here. Enjoy. Welcoming any feedback on this schematic - suggestions always welcome.

Vero Layout: The Gristleizer

Here's a really ugly vero layout I did for the classic 'Gristleizer' circuit, the first circuit I ever took a probe to and figured out how it worked. I learned a lot from the circuit, as it provides elements of electronics present in both guitar effects and synthesizers.

It certainly hasn't aged well, the filtering is pretty terrible and some settings are borderline inaudible, with some knobs not doing anything in 70% of their settings, and using 5 LM741s seems ridiculous, so this one uses a TL074 and a TL072, with the voltage doubler hidden off-board (I had this in console style case that I never finished). A lot of fiddly parts chained together.

I've built several of these now and they've all come off really well. FuzzDog does a great PCB if you're in the UK too: https://shop.pedalparts.co.uk/Gristleizer_-_Mad_Modulations!/p847124_15740439.aspx

Anyway, the layout:

I told you it was ugly!

I often wondered why nobody had produced a vero layout for this, and then as soon as I put pen to paper, I realised why. Too many jumpers, too many cuts and too many specific parts needed to commit to making this unless you really want to.

The schematic I made this from was a beautifully neat Eagle schematic which now seems to have been expunged from the internet. I have a copy but shan't post it here as I cannot remember where it was from and wouldn't want to host it without asking permission first. But if you fancy it, have fun building this.

Self-verified, as I had this working for a while, and it sounded near identical to the three I bought from Fuzzdog.