Background noise in compressor pedal

[neiltheseal]

Hi everyone.

I just put together an Aion FX Aurora (an MXR Dyna Comp clone). I've never used a compressor before but it seems to work properly, although with one issue.

When the pedal is engaged there is quite a lot of background noise, and when I turn the trimpot clockwise it becomes even louder.
Here is a video of what it sounds like.

https://www.youtube.com/shorts/afS-_c6K-Dg

Does anybody have any idea why I might be getting this background noise? Here's a pic of the PCB as well as a link to the build docs.

https://imgur.com/gallery/njahARB

https://aionfx.com/app/files/docs/aurora_documentation.pdf

[jimilee]

I'm only hearing white noise, is that what you're talking about?


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[neiltheseal]

Yes that's what I'm talking about.

I know compresssors can be noisy but this seems extreme. As you can see in the video, the pedal makes the white noise from the amp much louder. I wonder if there is a way to reduce this?

[mauman]

Try running guitar >> compressor >> amp.  If there's another pedal before the compressor, it will enhance that pedal's noise, compressors really like to be first in line.

Set the Input trimmer and Level pot for unity gain (meaning you get the same guitar level from the amp if you play softly, whether the compressor is on or off.) 

Then what happens when you play thru it?   

[jimilee]

White noise is typically from high gain, does t that one have an input pot?


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[neiltheseal]

Yes there is an input trimpot which is what I was adjusting with the screwdriver. Affects the noise a bit when turned to the left.

[neiltheseal]

Try running guitar >> compressor >> amp.  If there's another pedal before the compressor, it will enhance that pedal's noise, compressors really like to be first in line.

Set the Input trimmer and Level pot for unity gain (meaning you get the same guitar level from the amp if you play softly, whether the compressor is on or off.) 

Then what happens when you play thru it?

Thanks. I tried with no pedal in front with the pedal volume the same as the amp. The sound is still there especially when the sustain is at full and the trimpot turned fully to the right really increses it.

It does sound like it is essentially accentuating the amp's noise so maybe that is just a feature of a compressor.

Here are some videos of the pedal in action. I have a loop pedal in front of it. (Forgive the song choice, it was the first thing that came to mind). Does this sound normal?

https://youtube.com/shorts/EuaeoNVEd2w?feature=share

https://youtube.com/shorts/GFlobUpJ_Wk?feature=share

[mauman]

YouTube does it's own audio compression, so it's a little tricky to evaluate, but my impression is that your videos are in line with normal compressor operation.  Higher sensitivity (Input) and output  gain (Level) will result in increased noise when there's no signal.

[gordo]

It's hard to tell but a Dyna Comp will typically "pump" at high sensitivity levels.  You can hear it draw down the gain and then release it for a bit of an exaggerated compression.  Sometimes that's a cool thing, like tele chicken pickin stuff.  Sometimes it's annoying because it sounds too artificial or you get totally buried in a live setting.

Regardless, I'm really not hearing the pedal do any dynamics change and it should be pretty noticeable when that control is maxed.

[neiltheseal]

You are right. I was quite surprised how little this pedal actually did, other than create a bit more noise.

It does sound sound different live compared to recorded but it doesn't do a whole lot other than even out the sound so that loud and quiet playing is the same.

Do you think I did something wrong when putting this together?

[neiltheseal]

YouTube does it's own audio compression, so it's a little tricky to evaluate, but my impression is that your videos are in line with normal compressor operation.  Higher sensitivity (Input) and output  gain (Level) will result in increased noise when there's no signal.

Thanks again.

You have been a huge help for me in this and other posts. I really appreciate it.

[mauman]

You are right. I was quite surprised how little this pedal actually did, other than create a bit more noise.

It does sound sound different live compared to recorded but it doesn't do a whole lot other than even out the sound so that loud and quiet playing is the same.

That's a pretty good description of a compressor, it's subtle and mostly inaudible except at extreme settings.  The value is, as you say, bringing the loud and quiet sections closer together (compressing the signal peaks) so you can record or broadcast a signal with a higher average level, which gives you a better signal-to-noise ratio.  For performance, it can give your guitar more sustain by squashing the first (louder) part of a note and stretching the later (softer) part as it trails off.   It's kind of like riding the volume knob on your guitar to reduce the loud part and bring up the soft part of every note.

[gordo]

I'd post some close up shots and voltages.  The Dyna has a fairly distinct "puck" sound at full sustain, especially on single notes.

[neiltheseal]

Sorry if an obvious question. But where should I measure voltage?

IC, transistor? both?

[Aentons]

I'd post some close up shots and voltages.  The Dyna has a fairly distinct "puck" sound at full sustain, especially on single notes.

Right, I thought the dynacomp was the one for non-transparent "compressor as an effect" type sounds that are fairly noticable.

Like this:
https://youtu.be/JccW-mLdNe0