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...

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.

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...

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...

Does anyone have a schematic for this, or know how it differs from the Distortron i.e. just bigger caps for ins/out and feedback loop?

Pretty surprised to find this official Honey Bee schematic along with a DIY kit:

Might be old news to some, but I wanted to upload the schematic before it disappears.

Wasn't sure if I should bump the old BJF Honey Bee thread from 2009, the values all match up but I guess it is technically a different version. The old thread is a nice time capsule, pretty funny to see comments like I hear Honey Bee's are vapour wear and may perhaps not exist other than in cyberspace;)

I added all the...

Has anyone dissected one of the XTS iridium Fuzz pedals? Love the sound demos on youtube.
I have read that it has Red Llama DNA.

I want to build or purchase an affordable EL34 power amp, either 2x rack unit or small head format. Absolute maximum 50W, ideal 10-20W, as it is just for playing and eventually recording at home. Only power amp & phase inverter, no preamp, as i have a gazillion preamps either made or in the making for it, and a valve head already.

Any recommendations on DIY kits or ready-made products that have a good quality-price ratio?

Thanks in advance!

I was lucky to get Exar OD-1 in good condition for a reasonable price, so I thought I must trace it. Many legends are around that pedal, and pricing on the used market went too far, significantly after JHS added it as one of the modes in Bonsai pedal. I hope my trace will help reduce insane prices on those, sometimes higher than vintage TS ones.

original_5bb4449c-5f0c-4b62-84fb-47712bc87d1f_PXL_20230104_103012686.jpg

I got my unit with a box and price tag on it that says 370,000 PLN, and...

Davoli DTE 1051T.jpeg Davoli DTE 1051 T.jpeg Davoli 1051T 02.jpeg

The schematic is not complete, what are the stages to the right? And where's the ECL86 pentode stage?
Still the schematic lists the tubes as:
V1 ECC83
V2 ECC83
V3 6AV6
V4 ECL86

Is very much like the little pink amp a restored a few years back. That one was sold off, I just had too many amps around the house, and too little time to play them all. Little Pinkie was very wanted, just because of the color. But it also meant that I had to spend about 275 euro to wrestle it from the hands of some Flemish hipster soccer milf. It needed new tubes, a whole bunch of rewiring, filter caps and a new speaker. Then the guy who bought it haggle down to 350 euro, though I wanted 375....

Have some spill over on channel b and boost not working on one side and led light stays on on boost

Hello

I have been looking for a schematic for the ADA MP1 channel pedal, but no luck. This is the tube pedal. I looked at the VAULT ( and contacted MarshallJMP who sells parts for the old ADA devices.

I also looked to purchase one the pedals, but I do not see them for sale.

Please let me know if you have a schematic you could share, or maybe someone that has one and would be willing to take pictures.

Thanks
Rob

Internal view at 6m7s:

Another Exar pedals tracing, this time it is not one but two effects at once - MT-02 Metal and BM-02 Bad Metal. I traced both at once, as it appeared that they shared a single PCB.

PXL_20221231_150236846.MP.jpg
PXL_20221231_151241700.jpg

Both units seem to be manufactured same year - 1995 according to dates on potentiometers. I have boxes for both of them, but Bad Metal has a user manual, an Exar products catalog, and even a receipt from the store. It was old in 1997 in Warsaw for 77...

Hi, just reporting a repair on my 2006 MXR Dynacomp (rev E. with CA3080).

Problem was a frying bacon sound. I removed the socketed IC and audioprobed it. The noise was at both pin 2 and 3, so it was before the IC. Noise was also at the base of the first transistor, and up to the positive end of C2 (tantalum capacitor).

I replaced C2 with a good electrolytic, and noise is gone. Easy one, just make sure you add some leaded solder to the RoHS one before desoldering, makes it easier to desolder...

Many kilobytes have been spilled attempting to recreate the legendary Harmonic Percolator, and there are some that enjoy going to great lengths to find just the right transistors to recapture its classic sound. I'm more the type that wants to just shove any old BJTs in there and then jank with the rest of the circuit until it goes BRRRRRR...

I started with the Escobedo Harmonic Jerkulator:

Harmonic_Jerkulator.gif

Tim already did the work of finding sane values for a 2n390x transistor...

Hello all.

I recent spent a Whopping $10 for a UT-300 Ultra Tremolo.

Great sounding tremolo, but does anyone know how to modify it to make the LED flash at the tremolo rate?

Thanks

These TC Electronics pedals from the 1980s are tricky to work on and I'm posting this information for the benefit of all brave souls that take on repair of these iconic FX!

The potentiometer knobs are *NOT* a push fit, so the often-seen advice for using string or ribbon to pull them off will certainly not work.

If you gently remove the blue top by lifting/prising your fingernail or similar blunt instrument, this will reveal a screw which releases the knob. Lift the knob off gently as there's...

I traced Exar FL-1 Flanger from my collection 🎉. The unit should have been made in 1989 or later due to the dates on the pots (09-89). I even have the box 😅.

PXL_20221219_211836112.jpg

This trace was quite challenging due to amount of components on the small single-sided PCB.

PXL_20221217_195623135.jpg
PXL_20221217_191615264.jpg

As I started, I immediately realized that it was based on... Boss BF-2. But when I went to the LFO section, it was completely different. So it is definitely...

Hi all!

Just got this wah for cheap as the switch was dead.

Inside is a nice wah pedal! I replaced the switch with a qualitu TPDT, now it rocks!

(pics are on my instagram)
Rocktron - Classic Wah.JPG

I'm continuing to trace Exar pedals from my collection. This time it's FL-1 Enveloper filter. I have 2 of them, both made in 1993. I traced the one with the worse cosmetical condition because its paint was very fragile. The nicer one is on photos, with the box, warranty card, and instructions.
PXL_20221206_135104506.jpg
PXL_20221206_135123013.jpg
PXL_20221206_135143814.jpg

The PCB is a small single-sided; I traced it pretty quickly. It has two HEF4069UBP by Philips and one Motorola...

If a moderator wants to delete this thread for not being stompbox related then I totally understand.
Could you please let me know your specific reasons though?
Why am I posting this here?
[] I don't think that posting this to a computer-related forum would succeed - business interests would prevent it from seeing the light of day.
[] This forum supports the free exchange of information AFAIK.
[] It might benefit some forum members that use Windows Media Player.
[] Tenuous link - When you listen...

Hi all,

I picked up a faulty EBS Octabass pedal. It works, but when you are not playing, there are constant blips/bops. Essentially, if you even touch a string, you get some signal being generated. Sounds as if the issue I have is very similar to the one described in

I've done a fair amount of reading, and recall somewhere that it could be a pull down resistor (which seems logical to me). Is there an easy way to find which resistor it is from a schematic (the schematic is on the forum)?...

I needed an expression pedal and boy, this one is cheap!

M-audio - EXP pedal.JPG