Method to cut Hermod CPU noise in cv + audio path

Hi Forum and Squarp Team,
I’ve been trying a few options to reduce a noticeable high freq processor noise coming from the Hermod CPU that is insidious and hard to cut out of the final mix… i’ve tried switching power supplies (Frap Silta, then 4ms Row Power, the Malekko power) also moving to different skiffs that have no submixers passing audio to the main mix…but so far it’s not possible to cut out the processor whine. It seems to transfer even through any cv signals as well (transferring into the filter or VCO or VCA that’s receiving the pitch cv or modulation cv.
I’m looking for any suggestions how best to cut or reduce this particular frequency without totally cutting it from the final mix (with loss of much other high frequency content)… any tips or tricks how to isolate or remove would be much appreciated.

I was having a hideous high pitched sound when connecting two different cases together using Hermod.
It took me a minute to track down the problem, and it turned out to be the stock power supply which ships with the Intellijel 4U cases.

MeanWell GSM60A15-P1J
15v - 4A - 60W

When I disconnect from the main case, the noise was gone.

I posted a series to Instagram about this:
https:// www. instagram. com/p/BiaXjcRAJsc/

I corrected this swapping the GSM60A with a second PSU

MeanWell GSM90A15-P1M
15V - 6A - 90W

I happened to have a second for the main case around because of the grounding issues with a René which needed a different grounding scheme. When I use the GSM90 with both the main case and the 4U case the noise is completely gone (as shown in the instagram series.)

I’m relieved that for me it didn’t turn out to be the Hermod at all.

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Hi Sunshine,
This is invaluable intel!
Much obliged for sharing.
I’ll track down a different brick this week and give it a shot.
Loving the Hermod more and more so very happy to hear of potential easy resolve.

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I have exactly the same issues here.
@Tanzforsyth : Have you solved your noises and cracks in the cv + audio path ?
@Sunshine : Sorry but your instagram link doesn’t work. I’ve looked at the power supplies references, they have 2 differences, 60W versus 90W, and also the jack for plugging the power in the system. The 90W have more than 2 electrical points. It is the case, please ?
Mine is ever 90W, exactly same specs.
I have tried so many different configurations.
With SynthRotek deluxe power / 4ms Row Power, same problems.
I hear a sort of CPU noise in all my system outputs.
And the cv path is not clean at all ( 1v/oct swag a lot, causes a sort of chorus effect in mu 1v/oct MI Clouds input ) .
Many thanks for your help,
Hope I’ll can benefit of all the Hermod’s power :wink:

Got the GSM 90 brick and did the trick thanks again

The link is sanitized by this board. Sorry about that.
Take a look in the address bar and remove the 20% business and it’ll take you there.

I’m having a similar issue, hearing a faint CPU whine from the Hermod. While it’s minimal, it can still come forward in the mix after EQ and compression.

Knowing embarrassingly little about power, would I be able to use the MeanWell GSM90A15-P1M on something like a Make Noise case?

Answered my own question above (yes the Meanwell PSU works), but unfortunately I’m still hearing the whine. For what it’s worth I was also experiencing the whine with a Doepfer PSU3.

Wondering if this is something every experiences (and deals with) or if my unit is particularly loud for some reason or another. Do the rest of y’all hear it when the system is cranked?

Eh, was hoping find any solutions, and find friends in misfortune)))

My experience is 60 and 90w meanwell supply’s + doepfer, motovillo and L1, and in any combination noise is horrible, friend use separate power for hermod, but it not fully fix problem, if something from hermod connected to VCA, hiss comes back(

Is anybody speak with Squarp team about that issue? I’m in a step before sell it…

Hello guys,

We found a software fix that will be in the next hermodOS version, soon to be released, improving a lot the noise amount!

To provide full transparency, we never experienced by ourself this problem with Hermod (unless with a cheap power supply) and according to users, it seems quite rare. But thanks to some users of this forum we were able to find and fix the issue.

We know that ground problems can be really tricky to troubleshoot. I take advantage of this message to list here some advices, helping you to reduce the noise of a module:

  • try to change the module position in your eurorack case
  • do not screw the module to see if it reduces the noise, or maybe use plastic screws
  • try an other 15V power supply adapter
  • try an other case (or an other 12V/-12V/5V power board)
  • try an other power outlet in your studio, without using outlet power strip
  • use a linear power supply (the best way to get rid of noises)
  • if the problem appears only when you use the USB HOST, use a special Y usb cable that power your usb device with a separated supply

Have a nice day, and stay safe!

Is this fix added to latest version of firmware? I’m using 1.61 and Hermod is still making a lot of CPU hum.

yes, firmware updates are incremental.

as stated above, other modules and PSUs can cause issues, so this is worth investigating, as detailed by squarpadmin’s post.
if you continue to have problems you should contact squarp via their contact form

I mean I know that the firmware updates are incremental :slight_smile: I just wondering because I found no mentions in hermod firmware updates changelog, so I asked if this fix was ever added to firmware updates.

given timing of @squarpadmin posts, saying it was in next release (soon), I believe it was in 1.50.
no specific items, as just general improvements, I think it was just put under ‘code optimisations’ , and also the new feature to be able to reduce the led intensity (which can cause noise in some systems)

I’d recommend you review the above checklist, and the contact Squarp if your problems persist so that can hopefully help you directly.

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this is a tough topic… I work in industrial instrumentation and ground loops and noise is a common issue.

definitely think the quality of those switch mode PSU that people use are a factor and if interconnected racks with multiple psu rails, will cause issues also.

i would suggest ensuring all power comes from the same power board as the audio output system (speakers amps) but really the earthing system gets complicated and it isn’t safe to mess around with power.

I’ll see if I can come up with some more solid solutions

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