Troubleshooting Noise Within a Eurorack System

I’ve been having a lot of trouble finding the cause of some irritating noises within my eurorack system. This definitely crosses over into a few other thread topics so I apologize if this is redundant.

I was sure that the route of my problems was power related. I was using all uZues power modules and was told that they are an old design and not that high in quality. I bought a 4ms Row 40 with their power supply today but nothing has changed.

One of the problems I have is with the standard hiss you find in all audio equipment. I’m generally fine with this although it could be a lot lower. The bigger problem I’m having is with a ringing/whining sound. This sound is coming directly out from behind two of my modules face plates and it’s in the audio signal path too. The two modules are the Morphagene and the Just Friends. The sound is also in the audio path of random modules both on and off of the same power supply as the Morphagene and Just Friends.

So far I have switched out my power module, unplugged all other equipment while listening for the sound to disappear, bypassed my USB hub, disconnected and rearranged modules, and tried different ins and outs.

I guess my question is, how can I definitively find out that this is still a problem caused by power so I don’t waste my money on really expensive (and confusing) PSU’s/noise filtering bus boards only to find out the noise persists?

Have you tried using a different outlet or power strip? Those are often sources of annoying noise.

I recently solved an issue like this by running my modular into a passive behringer direct box with a ground lift. It got rid of the whining I was experiencing entirely. It was really a combination of using the balanced xlr cables and the ground lift.

Oh yeah I forgot to mention I have everything plugged into a Furman Power conditioner. I tried plugging that Furman into a regular outlet in my bedroom and an air conditioner outlet. Getting noise in both. It’s a little more difficult for me to try another room but I might have to at some point.

I have a direct box and it helped a lot with my pedal noise. Unfortunately this problem is happening throughout my entire modular system. I’m wondering now if I should try a ground lift adapter before going into the Furman.

I’m not sure, I don’t have any experience with a ground lift like that. This is just one right in the side box.

https://www.sweetwater.com/store/detail/DI400P

I used to have pretty bad noise problems… first I switched to busboards (Intellijel FWIW) from a uZeus which helped lower the noise floor and some of the general errata but not nearly enough, then I got a nice~ish transformer-based DI with a ground lift which helped a lot (this), then eventually I ditched the switching Meanwell I was using and threw in a linear PSU which seemed to eliminate the same noise I was nuking with the DI after A/Bing with the ground lift (what that’s about I have no idea). I’m not an EE ha.

4ms is a great company but I will say that the 4ms busboard doesn’t look like much more than the equivalent of a glorified flying busboard in PCB form. I might suggest saving and get a linear PSU, better busboards and crossing your fingers…

I haven’t had any of the whining issues some people have with the Morphagene and JF, dunno.

edit: oh yeah if all you did was switch the inlet module and to another switching PSU… probably not going to help much unfortunately.

Thanks this is really helpful!

Where in your setup is the USB hub that you mentioned? I get an irritating high pitched noise when using my Qunexus keyboard as a CV source if the Qunexus is running on bus power.

You mentioned disconnecting and rearranging modules but have you disconnected and reconnected (and listened to) the modules one at a time?

I don’t know about Just Friends, but the Morphagene does make an “acoustic noise” as Make Noise worded it, which isn’t in the audio path, but IIRC is basically something in the circuit which vibrates and produces that noise.
Now you know why they are called Make Noise :smiley: but jokes apart, that should be just a thing you hear when you are in front of the modular and not something you get in the audio.

Not an EE either, but I’ve gotten a bit into “noise paranoia” recently and have started to check all my modules and the PSU for noise… just to find out that yes my PSU (TipTop Zeus) does produce a bit of noise, but it’s so low I can totally ignore it. Still I had some big problems in the past and I wish I had known some things I now know back then. So here’s a quick list that might help you:

  • usually the noise comes from the PSU (except if it’s EM-related) and propagates on the 0V bus (confusingly often called “ground”).
  • if you have noise problems 99% of the time it’s due to having a switching PSU, so if you can, get a linear one, or at least a good hybrid one.
  • if your PSU does not connect to protective earth (the third pin of your wall wart) it might also worsen things in certain situations.
  • ground lifts sometimes work, sometimes not. If you’re just using the modular at home/in the studio that might be doing the trick, but if you need to use the modular in different places, better solve the problem from the ground up.
  • first of all there’s modules that inject noise into the system, and there’s modules that are prone to receiving noise. So I would also ask: did you try to put the modules into the case one by one to see which ones were causing the problems? Sometimes this is a matter of having a wrong circuit design, sometimes it’s an inherent thing to the circuit. For example: overdrives, waveshapers, preamps and VCA that go beyond unity gain will apmplify the noise in the circuit. So if these produce the noise, you need to find out where it comes from, because it’s not a problem of the module’s circuit being done wrong.

Also, about “noise filtering busboards”: I’ve done some research into the matter and to me it seems there is no conclusive proof that these actuallty do much more than cost money. What seems to work is to have a busboard system with a very low-resistance 0V bus. I.e. things like Hinton’s busbars or busboards with thicker copper layers, but that will be expensive.
Before trying any of that I would first try to find out what is making the noise, isolate that from the system, and see if you still have problems. If not… well I guess you need to replace those modules with some that are better designed.

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Man this is so helpful thank you. Are there any linear PSU’s you could recommend?

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Oh and another thing I just realized is that the power brick that came with my 4MS Row 40 is ringing and buzzing like crazy! I think it actually introduced more noise. I’m going to test each individual module for sure but I think I also need to return this Row 40 and get a nice linear PSU and good quality bus board. It’s not a good sign that the power supply itself is emitting a very loud noise. I also considered going to go with the Intellijel Triple Power Supply until I noticed it was switching. It does claim to be low impedance and low noise though.

It might at this point help to understand how a switching PSU works (hoping I’m not telling you things you already know, but from what you write it seems that you do not have a full understanding of these things).
Here’s my layman explanation, that does help me to imagine how these things work internally:
Switching PSUs lower the voltage by quickly switching the power on and off and then modulating the duty cycle of the on period. That’s why they are sometimes also called “digital”, since they work by using 1 (current flows) and 0 (no current is flowing) states. To me this is misleading and somehow silly, so I stick to “switching”. Anyway, the noise you get from these PSUs can be both in the audio signal and can be an acoustic noise from the brick vibrating. Both are common and both can be very annoying. Nearly 99% of all bricks that you get with electronic devices are switching, and I have a bunch of them here that do white and buzz in all sorts of ways. What brand of brick did they give you with the PSU, and does it have a “protective earth” connection?
Anyway, if it does make noises it might be normal, or it might be that the one you have is malfunctioning a bit, so better ask. I have both the Cincon brick that is used with the TipTop Zeus boards, and the very common Meanwell brick that many hybrid PSUs use, and neither of those does make any noticeable noise.

The Intellijel is – as far as I know – a hybrid design. This means that it uses a switching brick (in their case the Meanwell one) that does the heavy lifting to take the voltage from 220VAC (or 110VAC) down to 15VDC, and then they have a linear stage that produces all the voltages your modular needs from there.
The busboard is arranged using a “star” design, which IIRC means that all the connectors go directly to a central point and are not connected in series as in most Doepfer-style busboards, which lowers the resistance and makes the system less prone to noise.
Of course every PSU is being marketed as being low noise and all that. Only very few will give you actual specs. Intellijel does better than most in that they at least state the stability (which is rated +/-1%). I don’t know how to actually read these numbers, but I’d say it might mean that the voltages can oscillate for example between 1,88V and 12,12V, but that spec might be a “worst case scenario” as well as just the “typical” value.
1% is worse than a some good quality linear PSUs but seems good to me for a hybrid one. You can do some some comparing here if you want: https://docs.google.com/spreadsheets/d/17qu-PkyJnjZf9YzhNYy7X7-d-lmZqhahyUW0YM1b2N0/edit#gid=0

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There are two things I would do before putting more money into this issue.

First:

This is not standard. Unless have everything turned up 95% or something, you really shouldn’t have any noticeable hiss in your audio equipment. Perhaps investigate the cause of this and see if it’s related in some way to your modular issues. I have a memory of reading something years back where somebody had hiss issues in their audio system. The issue turned out to be that the property they lived in was older and did not have proper grounding. Not necessarily saying that’s what your problem is but it’s those sorts of things that might be worth looking into.

Second:

I see you’re in New York. You are lucky as you have access to at least one modular dealer there. Maybe take your problematic modules round to them and ask their advice. See if you can try them in one of their systems and find out if the ringing issue is still present. If it isn’t, then you can see what’s different between their setup and yours - it may give you somewhere to start.

Most busboards, like the Intellijel units, market a specific PSU but you can use whatever (e.g. subbing a linear unit) as long as the output is correct. Be aware that there can be a modest amount of wiring. Generally nothing excessively complex.

This seems like a good spot to bring up something I encountered while installing/testing modules in my brand new Intellijel 7u case last night.

One of the modules I installed is the Intellijel 1u Noise Tools. Curiously, noise from that module seems to bleed on through to the right outputs of the Cold Mac only, audibly following the rate of the clock or the random pulse depending on what’s selected. The path is simply any output from Cold Mac (with no inputs) to the Intellijel i/o tile and then from the balanced 1/4" outputs on the back to my mixer.

If I take an output from the Linix instead of Cold Mac to the i/o tile, that bleed from the Noise Tools seems to disappear. Any ideas around further debugging what seems to be a bleed problem between two specific modules?

my guess is that Cold Mac is more susceptible to noise pickup than other modules.

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Yeah, I figured that might just be the case. I was also monitoring with headphones, which I’m sure accentuated the problem last night. Testing this morning, it wasn’t so so bad.

It’s really unfortunate given how expensive all this stuff is but I’ve come to the conclusion that these noise issues are sometimes completely unavoidable. After I splurged on the Intellijel Triple Power Supply my noise leakage issues stopped but it didn’t solve any noise problems within individual modules. The Morphagene is still the worst offender. So after buying an expensive PSU and a Furman I’m still having noise problems. Next step is to buy Izotope RX and use it when things get really bad.

Noise problems are usually only really a problem in certain limited cases. If you’re making really quiet music, do lots of amplifying etc. I also have a module here which creates an audible noise and is being picked up by any mixer/VCA I have tried to far. It’s fortunately not being amplified by Ears, which would be a bit of a problem.
I did have a lot more issues with noise with my previous mixer but since adding the WMD performance mixer to the system that seems to be a lot better. The noise floor is so low I can’t hear it even with the headphones and the volume relatively loud.

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