Simple noise gate  [documentation]

Original effects with schematics, layouts and instructions, freely contributed by members or found in publications. Cannot be used for commercial purposes without the consent of the owners of the copyright.
User avatar
Matthes
Information
Posts: 11
Joined: 27 Aug 2022, 09:32
Has thanked: 5 times
Been thanked: 13 times

Post by Matthes »

Hi there!
I am new here and I would like to share a noise gate circuit that I have been working on.
One or two years ago I was playing around with the MXR noise gate circuit and I did a lot of trial and error modifications to it.
Then I forgot about it, until a few weeks ago I rediscovered this project and finially finished it.
It is using only cheap and standard components (and not many of them) and it could easily be added to overdrive circuits or similar.

I am really sorry, if there already exist similar circuits posted by other users - my intention is not to copy someone else's work.
And I have to say that I am not schooled in electronic circit builds and stuff like that.
So there may be some flaws in the design (however, for me it is working without any issues).

Regarding the circuit, I guess you could also use a dual opamp to add a buffer to the "key" output. But for me it works perfectly as it is.
Of course you can also try different cap values for the decay: larger ones for longer, smaller ones for faster decay.
If you do not what to use it in the FX loop, but in front of the amp, just connect "Key_out" and "Sig_in" (and go from "Sig_out" to amp input).

I build it into a pedal and I am using it with my amp (Mesa Mark V:25) for several weeks now - at rehearsals and live shows.
For my personal (!) needs it works perfectly and I am super happy with it (in fact it replaced my Fortin Zuul).
Maybe some of you might find it helpful as well.

Cheers,
Matthes
NoiseGate.png

User avatar
CheapPedalCollector
Resistor Ronker
Information
Posts: 399
Joined: 19 Oct 2020, 15:15
Has thanked: 452 times
Been thanked: 147 times

Post by CheapPedalCollector »

Is the 3904 inverted, seems the emitter should go to ground.

User avatar
Ichabod_Crane
Resistor Ronker
Information
Posts: 354
Joined: 26 Apr 2016, 15:11
Has thanked: 83 times
Been thanked: 36 times

Post by Ichabod_Crane »

Wait a minute! This replaced your Fortin Zuul? Do you mean you prefer this to the Fortin Zuul?
I built the Fortin Zuul for a friend and, thought I can't compare it to any other noise gate, I tested it and I was totally amazed by it. I found it really really good: transparent, no decay of the note, I could even get feedback with it on. And if I bypassed distortion the Zuul doesn't make anything wrong with the clean sound.

It will be nice if this works so fine because it's a very simple circuit.

User avatar
Matthes
Information
Posts: 11
Joined: 27 Aug 2022, 09:32
Has thanked: 5 times
Been thanked: 13 times

Post by Matthes »

CheapPedalCollector wrote: 13 Sep 2022, 21:41 Is the 3904 inverted, seems the emitter should go to ground.
Hi, I checked my build again and the schematic is correct (collector to ground).

User avatar
Matthes
Information
Posts: 11
Joined: 27 Aug 2022, 09:32
Has thanked: 5 times
Been thanked: 13 times

Post by Matthes »

Ichabod_Crane wrote: 14 Sep 2022, 08:02 Wait a minute! This replaced your Fortin Zuul? Do you mean you prefer this to the Fortin Zuul?
I built the Fortin Zuul for a friend and, thought I can't compare it to any other noise gate, I tested it and I was totally amazed by it. I found it really really good: transparent, no decay of the note, I could even get feedback with it on. And if I bypassed distortion the Zuul doesn't make anything wrong with the clean sound.

It will be nice if this works so fine because it's a very simple circuit.
That is correct (even though the Zuul is a great pedal, without doubt).
First I used it instead of the Zuul just to test it in a real band situation.
But now I still have it in my setup because I am not missing anything with it.
Compared to its simplicity I am amazed how well it performs (at least for my needs).
But again, I am not trying to bash the Zuul, it's a great pedal.

User avatar
Manfred
Tube Twister
Information
Posts: 1937
Joined: 04 Apr 2009, 23:42
Has thanked: 1671 times
Been thanked: 1344 times

Post by Manfred »

I miss the reference potential for switching the JFET, is there a resistor between souce and ground?
SimpleNoiseGateSwitch.jpg

User avatar
Ichabod_Crane
Resistor Ronker
Information
Posts: 354
Joined: 26 Apr 2016, 15:11
Has thanked: 83 times
Been thanked: 36 times

Post by Ichabod_Crane »

Is the KEY OUT optional or essential to makes it working?

(I tried to drawn a veroboard layout. Do someone want to see it?)

User avatar
bmxguitarsbmx
Cap Cooler
Information
Posts: 510
Joined: 25 Mar 2010, 21:15
Has thanked: 704 times
Been thanked: 216 times

Post by bmxguitarsbmx »

The Key input/output allows the muting to happen in the effects loop, so that it silences the most noise. But, the sensing of signal/noise happens at the Key Input as it has the least processing and cleanest signal to trigger a gate.

The mute jFet is ground referenced through the "KEY OUT" ground connection, which then would be connected to the send and return grounds of the amplifiers effects loop (or through the input and output of your distortion box). Doing it this way prevents ground loops. The mute Jfet does need to be ground referenced to work, as Manfred points out. Switching jacks could be used to pass the input from the "KEY IN" to the "SIG IN" jack when not trying to key an amp or distortion box, like Ichabod is proposing.

User avatar
bmxguitarsbmx
Cap Cooler
Information
Posts: 510
Joined: 25 Mar 2010, 21:15
Has thanked: 704 times
Been thanked: 216 times

Post by bmxguitarsbmx »

This 2n3904 is still blowing my mind. It is setup like a diode/level shifter sort of deal. Anyone care to explain it or link reference?

User avatar
Manfred
Tube Twister
Information
Posts: 1937
Joined: 04 Apr 2009, 23:42
Has thanked: 1671 times
Been thanked: 1344 times

Post by Manfred »

In the schematic a N-Channel FET symbol is drawn but the J175 is a P-Channel type.

User avatar
Manfred
Tube Twister
Information
Posts: 1937
Joined: 04 Apr 2009, 23:42
Has thanked: 1671 times
Been thanked: 1344 times

Post by Manfred »

bmxguitarsbmx wrote: 19 Sep 2022, 15:46 This 2n3904 is still blowing my mind. It is setup like a diode/level shifter sort of deal. Anyone care to explain it or link reference?
I ran a simualation from C4 parallel to R5, there a sine signal was fed.
At the emitter of the 2N3904 still about half the AC level comes out,
but the peak of the sine wave always cuts the 0 volt line and is completely in the negative range.
There is no DC voltage generated that could drive a JFET, I also wonder how that works.

User avatar
Matthes
Information
Posts: 11
Joined: 27 Aug 2022, 09:32
Has thanked: 5 times
Been thanked: 13 times

Post by Matthes »

Hey guys, appologies for the delay!
As stated in my opening post, I am not educated in electronics or circuit design.
The basic circuit came out by chance and I optimized it by trial-and-error changing component values.

All I can say that it works for me - I breadboarded (daes that verb exist?) and build it exactly as shown in the shematic.
After reading your comments, I breadborded it again to ensure I did not miss anything: It still works, as my previous build.

Maybe someone can simply replicate it on a breadboard?
It is really not hard to build and all components are easy to get.
It would be super cool, if someone who is actually skilled in these things could help to improve it.
(if it helps I could also take some pictures or even record a short video, but that would need to wait until next week)

Cherrs,
Matthes

User avatar
Manfred
Tube Twister
Information
Posts: 1937
Joined: 04 Apr 2009, 23:42
Has thanked: 1671 times
Been thanked: 1344 times

Post by Manfred »

Hi Matthes,
did you use the J175 type?

User avatar
Matthes
Information
Posts: 11
Joined: 27 Aug 2022, 09:32
Has thanked: 5 times
Been thanked: 13 times

Post by Matthes »

Yes, it is a J175 transistor.

And I was able to record a short video, just to show that the gate it is working.
I do not have my real amp with me, but I do have an AXE FX 3 that I used instead:
I used its "OUT 4" and "IN 4" to simulate an actual FX loop.
Of course all internal noise gates are turned off and I used a ridiculous amout of gain, just for demo purpose.
I try to add some pictures of the breadboard asap, so you can see all details to compare with my schematic.
Here the link to the video: https://drive.google.com/file/d/1O7tniAWsO3YppKD-ipCSJw83VAKCKpzx/view?usp=sharing

User avatar
bmxguitarsbmx
Cap Cooler
Information
Posts: 510
Joined: 25 Mar 2010, 21:15
Has thanked: 704 times
Been thanked: 216 times

Post by bmxguitarsbmx »

Manfred wrote: 19 Sep 2022, 16:36
bmxguitarsbmx wrote: 19 Sep 2022, 15:46 This 2n3904 is still blowing my mind. It is setup like a diode/level shifter sort of deal. Anyone care to explain it or link reference?
I ran a simualation from C4 parallel to R5, there a sine signal was fed.
At the emitter of the 2N3904 still about half the AC level comes out,
but the peak of the sine wave always cuts the 0 volt line and is completely in the negative range.
There is no DC voltage generated that could drive a JFET, I also wonder how that works.
Did you mess with the 250k threshold control? It may be acting as a voltage divider with the string of R7, R6, R5 to ground to turn the J175 off. Then, when signal is present the 2n3904 is rectifying it in the right way to turn the J175 on...

I really don't know. I tried swapping the 2n3904 for diodes and it killed the functionality. At least in the way I tried it.

It does work! I breadboarded it. Great job Matthes! I love a good mystery, especially when it works this well.

User avatar
Matthes
Information
Posts: 11
Joined: 27 Aug 2022, 09:32
Has thanked: 5 times
Been thanked: 13 times

Post by Matthes »

bmxguitarsbmx wrote: 20 Sep 2022, 17:15 It does work! I breadboarded it. Great job Matthes! I love a good mystery, especially when it works this well.
Thank you so much!
I wish I knew more about all the theory behind it.
So it is super interesting for me to read the comments by you guys who actually have the knowledge.

I already did some more builds: a modified SD1 overdrive, a remote switchable 3-band EQ, a 2nd order LP/HP filter pedal, ...
But I never really understood in detail what is going on (even though I do have some deeper knowledge in audio DSP).
I just kept tweeking until I got the results I was looking for.
Now I really want to get a better understanding of this stuff... It just makes the life of a passionate guitar player so much easier!

User avatar
EddieTavares
Breadboard Brother
Information
Posts: 126
Joined: 12 Jan 2010, 13:43
my favorite amplifier: marshall
Has thanked: 9 times
Been thanked: 26 times

Post by EddieTavares »

Hi

A friend of me did a similar circuit without jfet using a bjt transistor to shunt the signal to the ground, it is a very suitable add on to any high gain distortion circuit:

Image

User avatar
bmxguitarsbmx
Cap Cooler
Information
Posts: 510
Joined: 25 Mar 2010, 21:15
Has thanked: 704 times
Been thanked: 216 times

Post by bmxguitarsbmx »

Matthes wrote: 20 Sep 2022, 17:46
bmxguitarsbmx wrote: 20 Sep 2022, 17:15 It does work! I breadboarded it. Great job Matthes! I love a good mystery, especially when it works this well.
Thank you so much!
I wish I knew more about all the theory behind it.
So it is super interesting for me to read the comments by you guys who actually have the knowledge.

I already did some more builds: a modified SD1 overdrive, a remote switchable 3-band EQ, a 2nd order LP/HP filter pedal, ...
But I never really understood in detail what is going on (even though I do have some deeper knowledge in audio DSP).
I just kept tweeking until I got the results I was looking for.
Now I really want to get a better understanding of this stuff... It just makes the life of a passionate guitar player so much easier!
Yeah, well hopefully we don't have to wait around too long for someone smart enough to explain why the 3904 works as is... I'm a total noob in the DSP realm, so hopefully I can make something this good one of these days ;P

User avatar
Manfred
Tube Twister
Information
Posts: 1937
Joined: 04 Apr 2009, 23:42
Has thanked: 1671 times
Been thanked: 1344 times

Post by Manfred »

Did you mess with the 250k threshold control? It may be acting as a voltage divider with the string of R7, R6, R5 to ground to turn the J175 off. Then, when signal is present the 2n3904 is rectifying it in the right way to turn the J175 on...
Yes, I ran the first Simulation, with the 250k threshold control.
but the peak of the sine wave always cuts the 0 volt line and is completely in the negative range.
There is no DC voltage generated that could drive a JFET, I also wonder how that works.
I ran a new simulation with a threshold potentiometer setting of 50% and a sine wave input voltage of 3Vpp fed to the junction of C3, C4 and R5.
There I have to correct my statement in the post above.
Even if you do not see the generated DC voltage directly, it is the average value of the AC voltage completely shifted below the zero lines.
EmitterQ1.jpg
I create a PCB according the schematic above.
SimpleNoiseGateLayout.JPG
Ready-to-Print files:
SimpleNoiseGateComponentsSide.pdf
(13.99 KiB) Downloaded 250 times
SimpleNoiseGateSolderSide.pdf
(2.95 KiB) Downloaded 210 times
Sprint-Layout6.0 file:
SimpleNoiseGateLayout.zip
(14.69 KiB) Downloaded 177 times
Gerber files:
SimpleNoiseGateLayoutGerbers.zip
(11.07 KiB) Downloaded 142 times

User avatar
rcustoms
Resistor Ronker
Information
Posts: 426
Joined: 01 Oct 2009, 14:12
Location: COLOMBIA
Has thanked: 363 times
Been thanked: 520 times
Contact:

Post by rcustoms »

can work with any P-channel silicon field-effect transistors?
http://www.rcustomspedals.blogspot.com
guitars,pedals and amps.
@zuleta.rafael(Instagram)

Post Reply