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Hum, digital noise


I’ve tested my unit within three cases, one with a synthrotek power supply adn the two others with Pulp Logic post linear rev A.
In all cases, i’ve got a small, but noticeable hum, a bit like a hard drive sound. It seems quite related to the intensity of the display, and seems to be noisier when the display is more used.
Switching the user/admin/eject produces distinctive noises, especially from eject to admin.
The unit is never completely quiet. It simply get louder or different depending on what’s on the screen.
I tested with the 5V switch in REG and BUS positions with the same result.

Hum noise when on sample operations menu, pedal buffer menu
Hum noise when on sample operations menu, pedal buffer menu

Update :
in all cases, i am using the output 1U tiles from PulpLogic. Plugin my headphones directly in the ER-301 out doesn’t produce those noises.
I have a Monorocket case with a Circuit Abbey Unify output module to make further tests.


Update again :
i encounter no problems with my Monorocket case.
Still, let’s admit that the PulpLogic Output module is faulty, it doesn’t explain why the ER-301 is the only module i own creating this noise.
Any help would be welcomed.


Hi, the same happened to me with the Pittsburgh Outs!


i just moved my 301 to a pulplogic lbz54 case with the post linear 1A psu & 1u output tile. i’ll have a listen tonight and report back.


sometimes digital modules don’t play nice with analog modules. for example my monome ansible & grid combo is quiet, but when i use it to control a voice that runs thru the pulplogic spring reverb, or the doepfer wasp filter, audible digital noise is present.


I’ve had various modules that didn’t get along. Manhattan Analog MA-35 doesn’t like being next to Ataraxic Transalatron. Had to move Xaoc Batumi away from Pittsburgh Mix-mult because the LEDs in Batumi were bleeding into the mix audio as a high-pitched whine.

Sometimes position on your distro chain can change things. Like Metropolis was definitely happier closer to the PSU on my Synthrotek case. Further down the line it was graying out. (Even though there ought have been plenty of juice.)

Modular is weird.


just had a listen. there is noise. not a ton of noise, it definitely gets lost in the mix when there’s a bunch of stuff going on. but it’s there. and i did observe it changing with different processes - ie. loading a large sample into memory kicks it up.

tested it thru the PL spring reverb tile and that brings it out a little more, but only if the patch cables hang near the side of the case where the spring tank is mounted.

this is with the 301 power set to regulated 12v.


I’ll be purchasing a Pittsburgh Out (seems easier to get a hold of then the Pulplogic Tiles) to see if I can reproduce the problem and then determine the cause. Nothing concrete can be said until then.


After purchasing a Pittsburgh Out (still waiting for it to arrive), I came across this:


Looks like things are going to get confusing with all the revisions and hot-fixes that have been done on the Outs…oh well.

@eremitalf Can you post a picture of the back of your Pittsburgh Outs please?
@chapelierfou You too for the Pulplogic module please.


This is above and beyond the call of duty!!

While I hear excellent reports of customer service, from, well, almost everywhere, I never heard of a module developer purchasing another manufacturers module to try and work out any compatibility issues that may be there - amazing!


Hi Brian. I’ll try to do that later today when I get back home.



thanks for looking into this @odevices


here it goes @odevices


My Pittsburgh Outs arrived today and I did a BUNCH of tests on various power supplies and different ways of routing signal and I could not get the digital noise. :disappointed_relieved:

Although both yours and mine have REV7 written on the board there are at least 3 resistors that are not populated on yours but populated on mine and at least another 3 resistors with completely different values between your board and my board.

Also notice that your OUTS uses A50k pots (i.e. log pots) and my OUTS uses B50k pots (i.e. linear pots). So it could be that all the differences in the resistors are just due to the need to add tapering resistors to the linear pots to get a log response (which is the typical curve used for audio volume).

So results are inconclusive. Need more data.


i wanted to buy a zissou pulplogic case extra for the er301. now i´m not so sure…
i would not take the output tile, as i have a erica pico OUT.

anyone also has the “out” and a pulplogic case and could try out if this makes problems?


i tried monitoring directly from the er-301 when it was in my PL case and i believe it was all good… didn’t try running it through other modules though so i can’t comment on that.


Thanks. Yes I read that you did not had any problems than. But running it through other modules which are also in the pulp case would be interesting.
But you don’t own the Pico out, right?:slight_smile:


It’s maybe not helpful but i realized that you can just attenuate the outputs inside the ER-301 and run it straight to the mixer.