I wondered if I could swap the LED/LDR (or opto) for a FET, mosFET or 4049 gate (inspired by the PUP phaser series).

Here's the original:

I wanted to add a buffer, and that leaves me one opamp left on a quad, so I thought: What if I add dry non-inverted signal to the inverted filtered signal? The other frequencies should cancel out and the peaks should get peakier , right?

LTSpice kinda agrees:
( r being the resistance from point A and B to GND, where the opto is originally)

And a...

Just built a Foxx Tone Machine, and am having issues with the octave up being too harsh. It's basically useless other than single note playing

The normal fuzz sounds nice.

This build uses 3904 transistors and 1N34A Ge diodes.

Any suggestions on Q voltages, proper Q hFe, etc, would be appreciated.

Thanks in advance.

This is my first time posting here... I've been trying, for the better part of a year, to obtain this pedal. It beautifully replicates the sound of the Beatles - and much better than premium and expensive alternatives like Aclam's Dr. Robert or Jext Telez's White Pedal (no dis). Hear for yourself! Unfortunately the maker has gone completely AWOL... I was able to get a few replies from him last year but he disappeared. I think he's had enough with making pedals. His website and official social...

Hi,
I Have an MXR Analog Chorus that doesn't apply the effect:

- The original/dry sound passes trought the pedal, in both footswitch positions;
- Its a second hand Pedal;
- I don't have the diagram to troubleshoot;
- I disassembled the pedal and verified that the TP2 is missing, and instead, there is one resistor, with one leg in C16 and another led direct to one of the U3 pins;

I need some help trying to troubleshooting this. Sorry some english mistakes.

Hey all,
first of all I may be posting in the wrong section, so mods, feel free to move the thread wherever it should be.

So I've read here and there about DemonFX and how they might be copying the cosmetics of famous pedals but not necessarily their schematics. That seems a bit silly and I don't see what they would gain from only doing half of the job.
Also I have read on Reddit someone said that Josh @JHS had (reportedly) had a look at the AT-DS and said it was not the same as their AT+ and...

I’ve always liked phasers, in fact one of my first pedals I’ve ever built was a Phase 45 clone. Not only I liked how it sounded, another main reason for choosing it (other than the complexity) was that I only needed two matched JFETs instead of, for example, four for a four-stage phaser.
I’ve been sitting there, content with my box, for some years, until recently I’ve heard of the Project 447 phaser on an old ETI magazine. It wasn’t perfect by most accounts (the long string of 741 op-amps in...

Recently I posted my take on bazz-fussifying the Escobedo Push-Me-Pull-You . I've been so pleased with this little octave fuzz I thought it was worth playing with even more.

The PMPY is divided into two sections: A simple gain stage, followed by the push-pull circuit that cancels out the fundamental to give the octave. So, I got thinking, what happens if we add a second stage of fundamental cancellation? Well, it sounds pretty interesting, that's what.

So, building on my last circuit, I added...

Hello everybody, I was searching a sort of schematic for the concert bass mod , or at least some info on which component to change/add to realize it, starting from the classic double SHO design...
Anybody knows something about it?
Thank you!!
Gianmarco

Hi all.

After some trouble with my build i found a small piece of wire (with help of a magnifying glass and some patience) which was connecting the leads of two resistors. I also found a lead where the isolation was defective and one could see the bare wire. But i'm pretty sure the wire was not touching anything.
So far so good.
It is still not working. The Problem i Have now is that as soon there is a plug in the output Jack, the tip connection goes to ground. Tested with the beeper from the...

I'm trying to build a practice amp using an 8 Ohm speaker and a TDA 2822 IC that will run on 9v pedal power.

For a first attempt, I built the bridged example from the datasheet, shown here:

tda2822-bridged.png

It works, and it's a bit more volume than the usual LM386 amps I've built (ruby, noisy cricket, etc), but zooks its dirty. Like fuzz dirty. If I crank WAY back on the input volume it cleans up OK, but I'm just wondering if I can do anything to make that sample circuit play nicer...

Hi all,

This is my first post here so let me know whether I am posting in the wrong section, or anything!

I was wondering whether anyone had success building Tim Escobedo's Q&D VCF, or a variant of it (I understand that the topology is an active bridge-T filter, so variants might be published elsewhere).

simplevcf_252_119.gif

I put the second version on a breadboard with my guitar at the input and a digital cab simulation pedal at the output and all I am getting is a nasty metallic...

This post is mostly for documentation purposes and for future reference.
Maybe it can help someone fix their broken Holy Grail.

I recently got a used, older big box Holy Grail (pointer knob, Rev A, non true bypass)
Though advertised as 'in good working order', there was very little reverb.
Only with the reverb knob at around 4 o' clock (close to 100% wet) I could hear a faint reverb signal. At that point the dry signal had lost more than 90% of its volume.

Being familiar with the circuit I...

Hi.
I´m referencing the Abasi Pathos schematic from here:
I noticed every inverting opamp stage gets its own voltage divider + filter cap connected to the non-inverting input, and I´m asking myself if I could use a single voltage divider (instead of 6) like a plethora of other pedals, connect all Vrefs together and call it a day.
Does it mean anything to the sound or noise floor?
Is there any reason for dedicated voltage dividers at all?
I plan to route a PCB for this pedal and I can drop it...

Anybody ever mod an Arion Stereo Flanger? I could use any help I can get as all I can do is switch out parts, no real technical knowledge at this point. But I do like to take the stuff apart and put it back together, especially when it sounds so much better after changing a couple of parts. Anyway if anybody can give me some info thanks very much.

Looking for Dallas Rangemaster Enclosure with Graphics. I've checked with PigeonFx and they don't have any empty enclosures at the moment. Do you guys know of any other resources? Thanks!

Hi, Guys!

Some years ago my T-Rex Replica damaged due an issue with spike voltage. I tried to send my pedal to T-Rex, I didn't know what was the issue if it was Brazilian postoffice or IRS in Denmark, but the pedal returned to my home. I found a technician in my town that fixed SMD pedals, but this pedal according him it is complex, and he needs the schematic to try to fixed. I wrote to T-Rex, first its answer to change all the audio capacitors, but it quite difficult to him that wants to test...

I'm back to Exar pedals tracing, I was a bit busy during the last weeks, and it took me almost a month to finish HM-02 Heavy Metal tracing. According to the pots and warranty card dates, the unit I have seems to be produced and sold in 1999.

PXL_20230204_113433180.jpg
PXL_20230204_113459549.jpg

It was challenging to trace because of a lot of wiring with resistors in heat sinks attached to them. PCB itself is single-sided and transparent in light.

PXL_20230108_152117911.jpg

Because of...

I just built up a BB-1 using the V1 layout found here:

Everything works, voltages to the chip pins are all correct, diodes are 4148's showing .63v forward voltage when tested in circuit. The only change I made to the schem was to sub a 330K for the 220K for a little more gain. While everything technically works, I'm getting what I can only describe as too much clean signal on top of the distorted signal. The clipped signal is definitely there, but it just has a bit of this clean signal type...

I traced this one a few months ago and never got around to putting the schematic up here. The only thing that bothers me is how the 9v supply is hooked up to the cathode of the bypass LED. I still have the box but the owner is not willing to desolder the caps to find the values. Any way to measure them in circuit to get a rough idea of what the are? In my experience NP0/C0G caps are usually lighter in color....like a grey and the X7R caps are a darker brown so that's how I marked them on the...

Has anyone modded the GDI-21?
I think I'd like to add a mid control to it, True bypass, and fix the darn squealies the thing makes with EMG pickups.

I'm also considering using them as building blocks to build a 4 channel preamp.
I have a Tech 21 tri-ac that I love, and the Behringer GMX amp as a backup.
The gmx looks like two GDI-21 with a different input configuration on the jack.
The GDI just sounds like crap against the other two.