My second Muzzle is worse than the first?

[Elijah-Baley]

Hello,
I built a few years ago the Muzzle for a friend. I was really impressed by it! After I built it I test it with my friend: I used its TU-2 to split the signal, used the Input key and put the pedal in the loop effect. The 4 cable method. I tried the distortion channel of the amp but even with a DIY Triple Wreck in front of the amp.
This noise gate was incredible: zero hum and no loss of sustain or attack, and it didn't cut the feedback. And bypassing the Triple Wreck the clean was totally intact. Indeed we thought that this noise gate can be always on with no problem.

(Now I'm using some different gear: tube amp, a DIY Revv G4 and a DIY buffered splitter.)
This second Muzzle (the only difference is the new triplet smd chip) is not fully convincing. If I rise up the threshold enough to decrease a bit of hum I start to lose sustain and attack. I lose volume to decay of the note, it blocks the feedback. And it ruins my clean sound when I bypass the distortion.
I have to choice between still much hum or too gated sound.
What's happen to this circuit?

 

[jwin615]

Could it be that your effects loop output is too hot?
Some tube amp fx loops can output multiple volts p2p of audio. Maybe it's overloading the chip and it's going into protect mode? What seems like gating is actually a protective shutdown.
If your amp has a gain and level control in the preamp(not master/power amp), try turning down the level and see if that helps.

 

[Elijah-Baley]

I tried the Muzzle in the loop effect of my Laney LC50 and with the DIY Tonemender by ROG used like preamp directly in a solid state Crate amp (I cabled the Muzzle between the preamp and the power amp). In both the case the volume preamps are clean and low volume, just to test it in my room. I tried at least a pair distortion pedals.
I feel the gate even without a distortion pedal, thing I couldn't notice with my other Muzzle with the THAT4301, the one I don't have with me.

With both the amps I got exactly the same issue, I hoped that is a coincidence, even if I can't say why it doesn't work fine. But Moltenmetalburn has the same issue (Muzzle gates noise AND signal), and it seems clear that the RetroFit PCB works bad where the old THAT4301 work fine.

Moltenmetalburn, what's your amp?