Zakk Wylde ZW-44 Op-Amps and Gain Control

[kmc212]

Hello.

I have made a Zakk Wylde ZW-44 and have a couple peculiar things going on. The only op-amps that I have tested to be working are the OPA2134A and TL062. Has anyone been able to get other op-amps to work?

The other thing is the gain control doesn't adjust. The circuit only operates at full distortion all the time. I have the wire from the board where PIN 2 is to lug 1 on the pot then connecting to SW1A.  Should it be connected to SW1A first then to lug 1 on the pot? Or is it something else that would cause the gain control not to work? Thanks.


https://tagboardeffects.blogspot.com/2012/02/mxr-zw44-zakk-wylde.html

[Blackboarcult]

Any dual opamp with the same pinout (TL072, TL082, 4558, 1458 etc) should work, with more or less pleasant sounds. What opamps have you tried that don't work?

As for the gain, check the schematic: I'm far from an expert, but to my eyes both diodes and lugs connect to the same two pins in the IC. Order "shouldn't" matter as long as there is a direct connection between component lugs on each side. What the pot does is lower or increase resistance from the inverting input to the output, effectively increasing or decreasing dirt via the amount of signal passing through the diodes.

Make sure you don't have any bridge on your traces and that pots are not wired in reverse.

Hope this helps!

[kmc212]

Hello.

Thank you for the reply.

I have tried TL072, JRC4558D, MN1458, NE5532, LM308, LF353. None worked. It makes me believe there may be an issue with the circuit. I am using a 2N5088 transistor for Q1. Should the transistor have an effect? The distortion sounds very thick and fuzzy. It also cuts off quickly and does not sustain or feedback like a high gain pedal.  

I am going to check the pot to make certain the correct pot is being used. Sometimes I wire things incorrectly.

I did review the schematic and noticed the pot is after the diodes like any gain control. That's what made me question the wiring.
 
Thanks,

[ibanez48]

I think your main problem is the q1 you need the mpsa14 that it calls for. Mpsa14 is a darlington transistor. If u look at the data sheets on both the 5088 and the mpsa14 the hfe is way out of spec between the to the hfe is the dc current gain 5088 min is like 300 mpsa14 is like min 10000.

[kmc212]

I don't have the mpsa14. I have a mpsa13 and mpsa19. I'm checking the cross-reference list to see what else would be a good replacement. Thanks.

https://alltransistors.com/crsearch.php?mat=Si&struct=NPN&pc=0.31&ucb=30&uce=30&ueb=10&ic=0.3&tj=150&ft=125&cc=10&hfe=10&caps=TO92

[kmc212]

I have MPSA92 and not MPSA19.

[ibanez48]

Mpsa13 will work

[kmc212]

Thanks. I will give mpsa13 a try.

[LoriNagle]

Hello..I would never make my ZW-44 clone sound like the first. I had a unique gadget close to mine and I checked each damn section multiple times it actually sounds not the same as the first.

The significant contrast between the two is mine utilized uniquely through gap parts not at all like the first which is just SMDs. I utilized the first chip and info semiconductor even got the SMD diodes and stuff yet the sound is as yet extraordinary. It's working and sounds OK however dislike the first. I became ill of tweaking it and it's some place in a crate now.

printed circuit board