# That4305 issues



## Keith (Dec 9, 2021)

Has anyone built the muzzle with the new that4305 adapter board? Ive built 2 and both have the same issue , only gate when the threshold is maxed out , the key isnt working and it cuts off notes.. I have built about 10 to 15 of the regular 4301s and smds without any issues and just cant figure out whats going on.. I will prob it next to see if all passes signal. Thanks in advance


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## fig (Dec 9, 2021)

I don't think I've seen a build report on this configuration yet.
If your probe yields no obvious answers, I can populate and test mine. 
Also, decent pictures often lead to simple fixes.


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## Paradox916 (Dec 9, 2021)

I swapped out a 4301 for the retrofit module just to see if there was a difference and it actually preformed slightly better( not a ton, just marginally) Did you try swapping chips or put it in one you know works?


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## Keith (Dec 9, 2021)

When I had the switched tip going to the switched tip jack it would completely close the gate, I wired the switched tip to ground and it works as it should, . The only thing i did different was use a b20k as i didnt have any b25k so the sweep is slightly different but shouldnt be noticable..  I still think Im going to probe it


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## Keith (Dec 29, 2021)

Just an update for anyone interested,  I thought it was working after bridging the key however put in the enclosure and it was the same, the gate wouldnt close and the key does nothing.. I ordered a 4301 authentic chip for a ridiculous amount just to see if it still did it , popped it in and the pedal works as it should, the gate closes right away and the key works perfect.. I think both my retrofit modules of the 4305 have issues.


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## Robert (Dec 30, 2021)

That's very unusual.  I haven't heard of any other issues with the 4305 modules, two consecutive duds is even more puzzling.

Were these mounted with the component side facing up?


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## Keith (Dec 30, 2021)

Yes sir. I socketed 1 and hard mounted the other , both reacted the same way. If the knob was maxed it would gate but was muted notes and the key wouldnt open. Ive built many of these circuits without issue so I built a second one to see and it was the same,  swapped in a 4301 and it works fine. With the key plugged in I barely open the sweep for it to gate .


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## neequo (Jan 7, 2022)

I have similar issue with retrofit module - gate can not close, but only dim signal by some level. I have copy of Decimator and I know how good is it, so I see that Muzzle can't cope, something is very wrong with it.


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## Robert (Jan 7, 2022)

I'm not sure what's happening here, I've built two of these using the module and a few other folks have reported success as well.

If one of you wants to send the module back so I can check it out I'll give a refund (or replacement).


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## neequo (Jan 7, 2022)

In my case, the return shipment will be very expensive (I live in Poland)... Is there any simple way to influence the depth of gain reduction in this circuit? Changing the value of a specific component or some other way?


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## neequo (Jan 8, 2022)

Let me be more precise. The gate reduces the signal level satisfactorily deep only at the threshold setting in extreme regions, where we can only talk about a classic "tonesucker" (so we can forget about the intact articulation). However, when we set the threshold in the desired region (so the gate closes only when we are not playing, but soft or gentle excitation of the strings immediately opens the noise gate) then when we are not playing the gain reduction is very small, literally a few decibels. When we set the threshold a little higher, the soft playing is muffled by the gate but still quite audible, and a stronger strike of the strings opens the gate completely, so the action of Muzzle is more like an expander than a gate.
I checked twice, I have no soldering mistakes.


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## Keith (Jan 9, 2022)

The one I have socketed I can send to you if you want to check it out , I can also do a side by side video if youd like.


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## neequo (Jan 15, 2022)

Is there any chance to send me a properly working THAT4301 module? As I mentioned earlier, sending back the one I have is rather pointless, because the shipping cost from Poland is almost equal to the value of this module. Considering the costs I have incurred so far, it is quite an expensive disappointment (over $ 100 for my entire order and shipment, an additional 23% tax was imposed in my country). I ordered a few PCBs, but I cared about this noise gate the most. My order number is # 73866. I would appreciate your support.


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## Keith (Jan 15, 2022)

Theyre obsolete,  good luck finding a 4301


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## neequo (Jan 15, 2022)

I meant THAT4301 retrofit module: https://www.pedalpcb.com/product/ic-that4301p20-u/


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## Keith (Jan 15, 2022)

Its 4305 based and back to my original post about the issues im having with that module,  I ordered a 4301 for 40 bucks to rule out the chip being the issue but the 4301 worked perfectly so its clear to me I have 2 bad modules


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## neequo (Jan 15, 2022)

In my case, it looks similar. I checked my PCB work thoroughly, I did not make any mistakes, so only the said retrofit module remains the suspect  of malfunctioning.


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## jjmh83 (Jan 28, 2022)

Keith said:


> Has anyone built the muzzle with the new that4305 adapter board? Ive built 2 and both have the same issue , only gate when the threshold is maxed out , the key isnt working and it cuts off notes.. I have built about 10 to 15 of the regular 4301s and smds without any issues and just cant figure out whats going on.. I will prob it next to see if all passes signal. Thanks in advance


When did you order your module(s)? I'm wondering if there was a bad batch or something.

I'm having almost the exact same issue with mine. I've tried it with and without the key input, before the rack preamp I'm using it on, and after. If I set it high enough to kill the hum, it kills notes (especially pinch harmonics) prematurely, and also acts more like a volume control, like when I turn up the threshold pot, the volume goes down. If I set it low enough so it doesn't do that, it's not gating. If it's gated (as indicated by the bicolor LED) and I run my hand along the strings, I can still hear it at a much lower volume.

Using the key input performance is actually worse.


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## Robert (Jan 28, 2022)

There's only been one batch, but this is too many reports to be coincidence.   

I'm waiting to receive one of the defects back so I can try to determine what is happening.    I've tested several here and can't find one with a problem so it's puzzling.


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## fig (Jan 28, 2022)

I think I checked all mine, but I'll circle back because I seem to recall some noise but I haven't boxed it yet so that didn't really register at the time.


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## Keith (Dec 9, 2021)

Has anyone built the muzzle with the new that4305 adapter board? Ive built 2 and both have the same issue , only gate when the threshold is maxed out , the key isnt working and it cuts off notes.. I have built about 10 to 15 of the regular 4301s and smds without any issues and just cant figure out whats going on.. I will prob it next to see if all passes signal. Thanks in advance


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## Robert (Jan 28, 2022)

I'm going to dig out one of my Muzzle prototypes today so I can try to _hopefully_ make some sense out of what is happening here.


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## fig (Jan 28, 2022)

Robert said:


> I'm going to dig out one of my Muzzle prototypes today so I can try to _hopefully_ make some sense out of what is happening here.


I'll hire the bongo players and bribe the local constabulary


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## Coop (Jan 28, 2022)

I just got mine put together and I am in the same boat with it not completely gating and just making the string noise and such a lot quieter when it gates.  This is using the retrofit module in front of the amp only.  I don't have the key jack wired up so I have a jumper running between the pads.

Guitar > Greengage OD > Front of amp.


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## Robert (Jan 28, 2022)

I'm going to have to get one of the defective modules back so I can see / hear what you're hearing.

I've just tried two more retrofit modules (randomly selected out of the parts bin), the original hand-assembled prototype, as well as an original THAT4301 IC.   All four of these behave exactly the same.

I put a noisy fuzz cranked wide open in front of the gate then dialed up the threshold until the noise disappears.   I can still hear string noise if I drag my finger across the strings or gently drag the string across the fretboard like the intro to "Foxey Lady" by Hendrix, but the buzz and noise from the fuzz is gone completely, and there is no reduction in volume when I start actually playing.

The Muzzle doesn't behave like a lot of gates, the Threshold knob controls the threshold where gating happens, but it does also affect how fast/hard the gate closes.   It's not a matter of signal dropping below the threshold and the gate instantly clamps to dead silence, that's not exactly how it works.   According to the Fortin Zuul owners manual: "The ZUUL's threshold knob also controls the dynamics of the gate circuit."

I'm not saying that you _aren't_ experiencing abnormal behavior, but so far I have been unable to replicate anything out of the ordinary for the circuit.


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## Paradox916 (Jan 28, 2022)

Robert said:


> I'm going to have to get one of the defective modules back so I can see / hear what you're hearing.
> 
> I've just tried two more retrofit modules (randomly selected out of the parts bin), the original hand-assembled prototype, as well as an original THAT4301 IC.   All four of these behave exactly the same.
> 
> ...


can confirm the one module I got operates almost identical to the 4301 and the muzzle/Zuul buy design is atypical in operation in regards to others noise gates… that’s just my limited experience


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## jjmh83 (Jan 28, 2022)

I wish I knew someone with a Zuul to compare to. For me there's no balance between killing hum and not cutting off pinch harmonics early.

Before this, I was using my Axe FX Ultra (the old old one) with the gate block after my preamps in the loop, set to track the input (like the key input baically), and I never had any issues with it cutting off pinch harmonics or anything.


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## Robert (Jan 29, 2022)

Pay attention to this clip of the original ZUUL at the 2:12 time stamp.   You can see when the gate closes the signal is reduced (how much depends on the Threshold control setting), but it doesn't completely clamp to dead silence, you can still hear the guitar.   

This is normal behavior.


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## jjmh83 (Jan 29, 2022)

Okay, so I think this might be working (sort of) as expected.

So, first things first, the side chain drastically reduces performance for a noisy setup, at least mine. So first thing to do is get rid of that.

Second thing, I was getting a lot of hum, so I had to turn the threshold knob up to be quite aggressive. Turns out there's an EMI vortex or something on my floor where I had the pedal sitting.

So how I have it set up right now, I have my splitter which goes to my 2 boosts in parallel, a TC Pre and a TS clone I had from years ago, think Deadweald Duality. They run to the same output jack, then goes to my preamp (VHT GP3), then the preamp out runs to the Muzzle, then out to my power amp.

Things I notice when using the key input: unless I turned it up a fair amount, say maybe 30% of the threshold knobs adjustment, it just was not gating. I could hear the hum be reduced that I was getting through my cab, but the LED was not changing color. This was okay, it's better than nothing, but didn't really get me the chuggy staccato like palm muting chugs. If I turned it up a lot more, it was great for that... but nothing else. I attempted to just adjust it to where the red light came on while not playing with the guitar's volume turned up, but it still wasn't performing good at all. All dynamics were gone. I know I've probably said "pinch harmonic" like 20 times in this thread, but it's just kind of a litmus test for me. If I hit one, it would ring out for maybe a second then die.

Removing the key input from it, and turning it up maybe half way so it's gating based on my preamp output now, I can set it with the guitar's strings muted so it's just barely gating, and it doesn't kill dynamics.

Maybe I'm just not a fan of one knob noise gates, I'm not sure as I've never used one before this. Performance is acceptable now, but it seems odd to me that the "key" feature (pun quite intended) reduces performance for me. This is the selling point in what has become the gold standard for noise gates. Like I don't think there's any errors on the board that I've made, it's technically working, it's just not what I was expecting. I have a friend that also got a Muzzle and it's working well for him but I'm guessing my setup is quite a bit noisier. He's going to come over when he gets a chance so we can compare, maybe I'll see if he'll let me bang a key input on his for testing (he has it jumpered at the moment) and see if it's the same deal.


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## tetora 3786 (Feb 12, 2022)

I have zuul and muzzle. I have the same problem. I think the key input is an impedance issue. I plugged the buffered splitter  after the guitar to improve sustain and performance. Next, I switched from a single coil(HS-3)guitar to a humbucker guitar and plugged it in. The sustain is better and this seems to be no problem. The slide switch is on the right. As a result, buffered splitters and powerful pickups, especially buffered splitters, seem to be the answer. Because they sell a buffered splitter called Fortin roach. I'm sorry for my poor English, do you understand? I would like to try 4301 instead of 4305 with zuul. I wish I could get good results with any guitar, without a buffered splitter.


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## Dreez (Mar 12, 2022)

I had a problem with a cap in the feedback path not working. Exchanging the cap solved my issue.


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## Keith (Oct 15, 2022)

Robert said:


> There's only been one batch, but this is too many reports to be coincidence.
> 
> I'm waiting to receive one of the defects back so I can try to determine what is happening.    I've tested several here and can't find one with a problem so it's puzzling.


Did you ever look over the chip I sent back? I oredered a new one from the second batch with the same results , no gating but when I put in a 4301 the circuit works fine. Im stumped with the new adapters.


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## Keith (Oct 15, 2022)

Robert said:


> There's only been one batch, but this is too many reports to be coincidence.
> 
> I'm waiting to receive one of the defects back so I can try to determine what is happening.    I've tested several here and can't find one with a problem so it's puzzling.


I accidentally threw the old one in and thats the one that didnt work. The new one from the second batch works perfect. Sorry for the confusion.. thanks


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