DIY Noise Suppressors

[Steve Mavronis]

What 'classic vintage pedals' are the favorite DIY noise suppressor projects based on? For a 3rd project (after I finish my compressor clone) I'm looking for something again not too complicated circuit-wise if possible, that does noise filtering when not playing and doesn't have that annoying 'noise creep' while playing longer duration notes. I'm using a Boss NS2 which works as advertised, but the thing I really hate is that noise fizzle effect that creeps its way back to the tail end of notes while playing. Is there any way to also filter that out that noise creep without cutting off note duration in a DIY project? Can the noise frequencies be simultaneously 'split off' while notes are being played and discarded?

[Mark Hammer]

What 'classic vintage pedals' are the favorite DIY noise suppressor projects based on? For a 3rd project (after I finish my compressor clone) I'm looking for something again not too complicated circuit-wise if possible, that does noise filtering when not playing and doesn't have that annoying 'noise creep' while playing longer duration notes. I'm using a Boss NS2 which works as advertised, but the thing I really hate is that noise fizzle effect that creeps its way back to the tail end of notes while playing. Is there any way to also filter that out that noise creep without cutting off note duration in a DIY project? Can the noise frequencies be simultaneously 'split off' while notes are being played and discarded?

In general, the answer is "No", "Maybe", and "It depends".

Most users of noise gates and filters have a high degree of dissatisfaction with them, for precisely the same reasons that you note.  My own take on it is that this happens because use of a single noise-reduction pedal in one position requires it to do far too much.  Superior performance would occur if one used a pair of noise-reducers - one at the beginning and one at the end of a pedal chain - such that each could be used in a less heavy-handed, and more targetted, way.

The central problem is that "noise" covers a very broad range of phenomena and spectral content...and of course, sadly for us, so does the guitar signal.  The majority of noise-reduction devices rely on using the level of the overall signal (guitar + noise) to differentiate between wanted and unwanted.  And since there is often not much difference between the level of all accumulated noise, and the tail end of a soft note, it will cut the note tail as it chops out the noise.

In my view (and one I've posted here on many an occasion), a far better approach to noise-management of guitar signal paths is to use one noise-reduction device at the head of your signal chain, immediately after the guitar (or darn close to that position), which explicitly targets hum.  Early in the signal chain, there is precious little hiss, such that a device which exclusively targets that objectionable low-frequency hum and buzz can be quite effective without having to impact on the brunt of the signal.  One might experience a wee bit of bass loss, but the rest would come through ably.  Since that hum at source will not be magnified by passing through assorted gain stages, by the time your signal gets to the last cable to the amp, there should be precious little hum to contend with.

What does accumulate through your pedal chain is hiss, particularly in those pedals that apply large amount of gain.  If all you're forced to deal with, at the, end is hiss then it becomes easier to manage via a simple sliding low-pass filter.  Moreover, any side-chain used to drive the filter can focus pretty much exclusively on the envelope of content above, say, 3000hz or so to determine whether action needs to be taken.

Ultimately, when it comes to noise, divide and conquer.  If one plans to use a single pedal to manage noise, then it's plug in and grumble.

And, as I always do, I'll put in a little plug for the excellent noise-reduction properties of the SSM2166 chip.  It not only provides hiss-free compression, but can clean up the signal nicely for the rest of your pedals, requiring only very light gating at the end of the chain to manage cumulative hiss.

[amptramp]

One hobby of mine is to collect and restore antique radios.  One radio I have, an RCA A-33 has an interesting noise reduction scheme: it reduces the treble for low signal levels.  It does this by using a reactance tube as part of an audio filter and detecting the average signal level and using it to control the gain which in turn controls the effective capacitance and reduces the high-frequency rolloff for low signal levels to reduce noise.  There have been a number of similar "single-ended noise suppression" circuits (as opposed to double-ended circuits like Dolby that record the music in a predistorted format that is then corrected in the playback end).  A voltage-controlled filter is a standard building block for analog synthesizers and it may do what you want.

[Steve Mavronis]

Thanks guys for the above viewpoints. I'm curious of various strategies employed by companies like Boss and MXR to deal with noise. Boss having an effects loop built into their NS2, which for my meager setup of one dirt pedal doesn't seem to help much. Can anyone compare for me the diference between the 80's MXR Noise Gate and today's MXR Smart Gate? The newest MXR Smart Gate also has an extra filter switch for different ranges of noise (hiss, mid, full) but is it effective?

http://www.jimdunlop.com/index.php?page=products/pip&id=255

I was trying to explain the noise fade-in while playing issue to my father the electronics design guru. He thinks there could be a way to design a better noise reduction circuit to handle this problem but that may be wishful thinking until we experiment. That's why I'm curious if the extra MXR Smart Gate features works a little better than the Boss NS2 in this respect?

[Scruffie]

Best I can manage is a list of possible projects that I know of :-
Tonepad MXR - Noise Gate V1 & 2 (as you already seem to know)
DOD - 230 Noise Gate
EHX - The Silencer
BOSS - SG-1 (Not a gate in the usual sense but It did work to cut out noise with the controls down so it didn't swell and it is a gate in design so i'll include it)

This thread might be of some use - http://www.diystompboxes.com/smfforum/index.php?topic=81918.0

[Steve Mavronis]

Thanks for that link and did you ever build a DOD 230 and if so how is it?

To further illustrate the problem I'm annoyed with watch this YouTube video of Yngwie Malmsteen giving a backstage dressing room lesson:

http://www.youtube.com/watch?v=hLa6iW7dRf4

At the end of some riff examples he plays you can hear the Boss NS2 noise sizzle enter the mix on the last note if it's held a bit longer. I'm not sure if the very first one when he goes "whoa" is this or not but if you listen closely to later examples you can subtly detect it at the end of passages.

[Scruffie]

I'm just waiting on the Opto to come in the post at the moment, but from all reviews - http://www.harmonycentral.com/products/93077
Seems like a good pedal, can't get much simpler and there's already a nice Onboard pot layout about for you 

Yeah alot of people like the NS-2... I am not one of those people... the 230 is a gate as opposed to a supressor so the shut off should mean it wont fizzle out slowly.

[slacker]

Simplest noise gate in the world and very effective is pinky and volume knob

Do you mean the noise effect at around 23 seconds? I don't think there's much you can do about that, that's caused because he's stopped playing and muted the strings so the noise gate does what it's supposed to and lowers the volume, so you hear a bit of the hiss and then it mutes it. You could speed up the decay time, but then you run the risk of cutting off the end of the notes. This goes back to what Mark said about the level of the signal being too close to the level of the noise.
What would be better in my opinion would be to not completely mute the noise just reduce it to an acceptable level, that way the effect wouldn't be so obvious.

[deadastronaut]

Simplest noise gate in the world and very effective is pinky and volume knob

+1 on that....or use a different gain pedal, that doesnt hiss like *#^"...

volume pedal is cool too...especially the ones with the level knob..

it can be set to be overdriven to full on gain for solo's depending on setting, no need for pinky's either.

[Steve Mavronis]

All dirt pedals add noise so that's a given. At least my DIY 250 clone is 'less' noisey than the YJM308 that I was using and without the excess treble too. I love the midrange overdrive tone however so I'm sticking with that. I think my standard Strat stock single coil pickups are causing most of the problem plus the AC outlet 60 cycle hum is a big factor too. The in-between pickup positions are quiet acting like a humbucker canceling guitar noise. The NS2 does a good job except for the noise fade-in at the end of notes. I'm just wondering how noise suppressor circuits could be improved somewhat through DIY pedal building. I'm trying to determine if I were to base a clone on a vintage noise gate/reduction type pedal if it would be worth it especially if the end result is the same as what I've got.

[Scruffie]

All dirt pedals add noise so that's a given. At least my DIY 250 clone is 'less' noisey than the YJM308 that I was using and without the excess treble too. I love the overdrive tone however so I'm sticking with that. I think my standard Strat stock single coil pickups are causing most of the problem plus the AC outlet 60 cycle hum is a big factor too. The in-between pickup positions are quiet acting like a humbucker canceling guitar noise. The NS2 does a good job except for the noise fade-in at the end of notes. I'm just wondering how noise suppressor circuits could be improved somewhat through DIY pedal building.

If it's your single coils I can't reccomend shielding your guitar enough, my shielded strat is completely silent, not a bit of hum on it.

[Steve Mavronis]

If it's your single coils I can't reccomend shielding your guitar enough, my shielded strat is completely silent, not a bit of hum on it.

I know it's a separate topic but how did you shield your strat better?

[Scruffie]

If it's your single coils I can't reccomend shielding your guitar enough, my shielded strat is completely silent, not a bit of hum on it.

I know it's a separate topic but how did you shield your strat better?

http://www.guitarnuts.com/wiring/shielding/shield3.php
Star grounding, copper shielding (aluminium will be fine, I just used it as you can solder it) and also, some very basic protection from tube amp failure which isn't usually offered 

[Joe Hart]

Simplest noise gate in the world and very effective is pinky and volume knob

+1 on that....or use a different gain pedal, that doesnt hiss like *#^"...
volume pedal is cool too...especially the ones with the level knob..
it can be set to be overdriven to full on gain for solo's depending on setting, no need for pinky's either.

I agree with the volume knob thing -- I use it ALL the time (mostly to kill feedback and string noise).  I also do the volume pedal thing.  I use it a lot for cutting out noise (and silent tuning).  But I totally disagree with the "use a different gain pedal" comment.  I have a humbucker equipped guitar that is pretty dang quiet, into (among other things) a wah and a DOD 250 clone and LOVE my tone!  I've tried different distortion pedals and nothing really gets me the sound I want.  And with the wah and 250 on, it's noisy, but I deal with it.

I think Steve may be simply looking for something that will fix a problem he (and many others) is having.  Nothing wrong with that.
-Joe Hart

[Steve Mavronis]

I totally disagree with the "use a different gain pedal" comment.  I have a humbucker equipped guitar that is pretty dang quiet, into (among other things) a wah and a DOD 250 clone and LOVE my tone!  I've tried different distortion pedals and nothing really gets me the sound I want.  And with the wah and 250 on, it's noisy, but I deal with it. I think Steve may be simply looking for something that will fix a problem he (and many others) is having.  Nothing wrong with that.

Yeah, in loving your dirt pedal of choice (gray spec 250 Overdrive in our case) you accept the added noise it brings and the NS2 noise gating part is fine. I'm just trying to see if it's possible to filter out as much 60 hertz noise amplification fading back in while you're playing when it's not being gated.

[petemoore]

  Kindly spoken, I can see where a noise suppressor could be useful.
  For these situations I use a bypass switch.
  If high gain / compression is used, by definition any input [including noise] is boosted to 'max' or close enough that noise is suffieciently ugly to consider Supressor circuit.
  Transition between 'closed' and 'play', when noise is 'maxxy' will tend to confuse the threshold detector if any playing dynamics include low-volume passages as signal volume you want to hear is less than the noise.
  A 'blip' of noise of course will get through as it 'turns on', I've heard this used in a musical-modern-metal way or as added unwanted punctuations to the music.
  Another approach is: get rid of noise and keep dynamics [eliminate ground loops, continue to peel the onion layers of noise reduction, cry between each layer],
  Perhaps a sound from a circuit that 'naturally gates' can be found, exhibiting the ability to have its gate stage rammed with enough input that when played, it is driven 'open' predictably. 
 
 

[deadastronaut]

wrong post, thought you wanted a noise gate...nevermind

btw arent 741's inherently noisey?...i read that on a few sites..,

[Steve Mavronis]

Yes they are noisey in that they gain amplify everything going through them, your guitar signal and any 60 cycle hum and pickups or anything else before them, etc. The point is the noise "fades" back into the signal from the NS2 with a sizzle effect. Before that, for a moment, it's a nice "noise reduced" 741 overdrive sound. The 741 is amplifying the noise not being filtered out going into it. I know there are many who say the 741 has been around too long and there are better modern op amps. So why clone vintage pedals at all? Because with all its issues the modern stuff just doesn't capture the so-called grail tone based on days of old that we are after. Do you know any distortion pedal (or amp?) that doesn't amplify noise as you increase the gain? I get the same noise suppressor annoyance with other dirt pedals like the DOD YJM308, Boss DS1, and the old Ross R50 Distortion - none of them use a 741 op amp. So it's not purely a "741 issue" or let's all play clean amp tones or acoustic guitar and not use any noise suppressor at all. I find it interesting though that even the 70's/80's MXR Noise Gate used two 741's in it's circuit.

[anchovie]

I find it interesting though that even the 70's/80's MXR Noise Gate used two 741's in it's circuit.

The clue is in the name - it's a gate, so it mutes the output when the input signal falls below the threshold setting. Doesn't matter so much if the 741 adds a tiny bit of hiss to your full-whack overdrive sound!

Steve - I'm guessing that you've played around with your NS-2's threshold, decay and mode controls and you find that you either get the sizzle or get cut off too abruptly. There is a point on note fade-out where your vibrating string becomes roughly the same amplitude as the buzz from your single coils. I don't think the NS-2 (or most noise gate/suppression pedals) is clever enough to know which is which. I think your choices may well be to take the sizzle, take the abrupt cut, try out a Decimator/other fancy rack unit in a shop or look into shielding your Strat and/or replace the pickups with noiseless single coils or stacked humbuckers. I appreciate that my own personal approach of playing with so much distortion and volume that held notes will feed back until I switch off the dirt box isn't for everyone.

At least you can take it as a consolation that you have video evidence of the problem happening to Yngwie!

[Steve Mavronis]

Yep. That's why I'm also interested in the new MXR Smart Gate with the selectable 3 band hum/mid/full noise filtering added feature. Maybe having the addition of that extra filtering would help out for this kind of issue as a DIY project.