Muzzle (classic) only giving out the noise signal and mutes when guitar is played (works vice-versa)

[snoisiV]

Hello everyone!

I am trying to get the Muzzle working, but I am stuck at the moment on what to do next. I can only get the gated signal (the noise) out of the pedal. This means, if I play the guitar the pedal turns quiet and the lower the guitar signal gets, the more noise gets out. This even correlates with the knob. If I am turning it up, the noise gets louder and if the knob is all the way down, I can barely get a signal through. The PCB I use for the THAT 4301 is self-made but the same layout as the one on PedalPCB.

For troubleshooting I have bypassed the "switch" to ground in order to turn the LED on. When playing the guitar, the LED turns from red to green and the output signal from the Pedal gets silent. When the guitar signal fades, the LED turns back red and gives out the noisy signal. The threshhold loudness when the pedal turns on is correlating correctly with the potentiometer. So, everything works as intended but the output signal is the wrong way around. The pedal is tested using a test box. The test box has been tested with other boards that function properly inside the test box.

This is what I did so far:

- Tested all Transistors in a test device for proper function (no problems detected)
- Re-flowed some solder joints (no problems detected)
- Checked all resistor and capacitor values for correct values (should be correct)
- Cleaned and rinsed the whole board with isopropyl alcohol (no problems detected)
- Exchanged both ICs (not the THAT 4301) for new ones (no problems detected)


Something has to be "upside-down", but I can't see what it could be. Any help would be really appreciated.

 

[Paradox916]

The led should be indicating regardless of the pass through/key jacks, start by checking Q3 and Q4 is operating properly. And work your way back That’s my first suspicion there is really no reason you needed to socket the transistors in this application and there is a reasonable chance this isn’t your issue (or only issue)the sip sockets do remain suspect for a bad connection.

 

[jcpst]

Huh, that’s actually something I’ve been wanting to make!

My plan for doing it was to build a muzzle classic, splitting the input, inverting the side that isn’t going to the circuit and then combining them at the end to get the behavior you describe.

I wonder if that’s effectively what is happening here…

 

[snoisiV]

I have already checked if all 2N3904 are connected properly and they are. You are right, I should not have put them into sockets, but I assume it's harder to solder out the sockets now. I have also checked all transistors if they are working correctly and are not defect and all of them are working properly and give out the correct values.

Furthermore I have exchanged both ICs, the TL072 and the TC1044S, for new ones and the problem stays exactly the same. Unfortunately I do not have any further THAT4301 boards here to check if that one is working properly.

What really bugs me is that the pedal is working absolutely correct but just vice versa. It gives out the negative signal (= only the noise that should be gated) and mutes as soon as the signal gets stronger.

 

[Paradox916]

What a sec where did you get the tl072? that one in your pic is a fake…. Never mind looking at the wrong IC. I could be mistaken but I don’t know if the tc1044 is a good sub for the tc1054… and unfortunately there might be an issue with your retrofit module

 

[snoisiV]

I got mine from Tayda and did not observe any problems so far. Any way I can check them if they are legit?

 

[Paradox916]

You are probably good although I have received one or two 072s from tayda that weren’t necessarily counterfeit but you get a dud now and then.

 

[snoisiV]

The build documentation allows to exchange the TL1054 for the TC1044 in case the pads below the IC are soldered together (which I did).

 

[Paradox916]

The build documentation allows to exchange the TL1054 for the TC1044 in case the pads below the IC are soldered together (which I did).

sorry I forgot about that feature on the newer boards. You are correct

 

[snoisiV]

I currently have a suspicion that the main mistake lies somewhere at the point where the sidechain is normally connected and where I bridged the Tip and 3rd pad. However, in all pictures where the sidechain was left out, these 3 pads were connected and also the build document refers to that. Generally it feels like I am transferring the sidechain signal to the output but I really don't understand where this is happening.

 

[Paradox916]

I had a similar problem (if I remember correctly) with the newer board and there was a trace that wasn’t connected between Q3 and Q4 just for s and gigs check the board for continuity at these points.

 

[snoisiV]

I have fully checked all connections of Q3 and Q4. Nothing wrong over there, "unfortunately"
.

 

[Paradox916]

Well it was worth a shot… mine was probably a one off manufacturing error. Starting to look like something might be up with the module. This one is always a tough one to troubleshoot.

 

[snoisiV]

I can also confirm that the LED is working properly. I have now fully soldered the pins in and the LED turns green when it let's the signal through and goes red when the noise gate is activated. Basically the whole Effect works as itended, but the signal that is given out, is just the noise and not the signal without the noise.

 

[snoisiV]

Took some new, better pictures of the pedal and the solder joints and updated the initial post. Any idea what to check next or what to do would be really appreciated. Any idea, how to test if the THAT 4301 is functioning correctly?

 

[guitarbruno76]

Hi snoisiV, just an idea and especially for your request about Ic That4301 to check, at least the good signals towards it, could you check your signal circuit with an audio probe?
A record of your audible manifestation with the Muzzle could be useful....

 

[fibz]

Here‘s a shot of mine. The only difference I can spot is that you’re threshold switch is another type. Cannot see it but maybe it’s touching the 4305 IC?