Same here, lots of noise when powered from rack. Also when connected to ethernet it seem to take too much from the supply. Now I run from external power supply and run into ground loops.

I am doing some more investigations with various grounding options. It seems that powering from USB is by far the quietest option so far (~90dB SNR when plugged into a (almost full on) mic preamp). Will get back with more details.

8 months later

Has there been any developments with this? I'm having terrible noise issues using the pepper in a rack.

Hi, my investigations didn't yield any promising result, unfortunately. We designed a rev2 board which is being manufactured right now where the output circuit from Salt is used for the audio outs, which gives much better performance (-5V to 5V outs, much less noise).

    5 days later

    Ah, that's frustrating. The noise at the moment makes it pretty unusable. I've been having some luck taking out the noise with an external EQ. Would it be possible to program an EQ into the running patch or does the noise come outputs themselves, after the patch?

    giuliomoro do you think we could some how 'hack' the rev 1 board to do something similar?
    perhaps cutting traces, and putting on extra circuit on a small 'daughter' pcb?

    Id be happy to get a rev 2 board, and I could theoretically pull off the main components which make up most of the cost (jacks, pots, display, button) . but its quite a lot of desoldering and subsequent cleaning.. and tricky to remount on new board (as legs are obviously cut/shorter).

    ... I'd have 2 peppers to do ... thats said, the one in my 'dev' case could probably stay 'as is'

      That's a neat idea, and probably not totally undoable, but there are all of these components to fit in there...

      alt text

      6 days later

      On Thursday, we placed the order for the PCB breakout. Once verified, we will ship it out to any Rev1 Pepper users who ask for it, free of charge.

        giuliomoro wow that’s awesome !
        Thanks to all for making this happen.

        Perhaps you can drop a couple of them ( 2 peppers 🙂 ) in with my Trills 🙂

        No rush, and I guess the trills will be going out soonish ?! ( excited for those to arrive !)

            thetechnobear No rush, and I guess the trills will be going out soonish ?! ( excited for those to arrive !)

            Soon hopefully, they should ship from the supplier next week, but these days you never know.

            thetechnobear Perhaps you can drop a couple of them ( 2 peppers 🙂 ) in with my Trills 🙂

            We'll keep that in mind, let's see if the timing works out.

                  I will write here the instructions needed when we find the best way to do it. It's going to take a couple of weeks before we receive the PCBs

                  a month later

                  Hey there, Have there been any developments with this?

                  Hi Neil,
                  parts came in a couple of weeks ago, assembled and tested 10 days ago, then last week just disappeared because of shipping Trill. We are just picking up loose threads now. See announcement below

                  EVERYONE who has bought a rev1 Pepper and wishes for a radical improvements of the poor signal-to-noise ratio of the audio outs, we now have a remedy:
                  a dedicated PCB breakout for the circuit above which can be installed between the Bela cape and Pepper.

                  We are happy to ship out free of charge. Just email robert [at] bela . io for further details.

                  @thetechnobear , yours are in the post with your Trills already.

                    10 days later

                    boards arrived with my Trill - yah 🙂 (thanks again)

                    a couple of questions:
                    (assuming above schematic is unchanged)

                    a) I assume all caps are non-polarised

                    b) C11 &C18 - what values - 1n?
                    if not do you have a pcb schematic - as the capacitors are hard/impossible to read 😉
                    but if they are all 1nF, then its no issue 🙂

                    c) voltage at top
                    it looks like (from top) -12v gnd + 12v, but there are 6 points...
                    so I use the ones with squares?
                    if so what are the holes without squares around for?

                    d) J1 pinout
                    I assume this is for L-/L+ R-/R+ in, and L-/L+ R-/R+ out... but I don't know which is which 🙂

                    e) fitting to Pepper...
                    how would you recommend to adapt pepper to use this board.

                    f) opamp
                    I don't have any NE5532N (I think thats what shown above)
                    but I have some TL072CP, that are the same pinout.

                    of course, happy to go buy some NE5532N, just means I'll have to wait a week or so for them to turn up 🙂

                    g) any other changes?
                    whilst I have Pepper taken apart, would you recommend any other changes?
                    e.g. you mentioned a different regulator, but from your graphs above that seem to have minimal impact
                    (if Im placing an order at mouser, may as well order other things i might need 🙂 )

                    thanks again for all your help
                    Mark

                      I think @bela_robert has a small build guide drafted, which should answer most of the questions.

                      thetechnobear e) fitting to Pepper...
                      how would you recommend to adapt pepper to use this board.

                      This is the hard part. There is a bit of desoldering involved. We tried with some reduced-height headers, which seems to be working fine. Robbie should have some pictures/descriptions.

                      thetechnobear f) opamp
                      I don't have any NE5532N (I think thats what shown above)
                      but I have some TL072CP, that are the same pinout.

                      I think it should be fine. Not sure there is enough vertical headroom for socketing your IC, though, so ... you are committing to one or the other!

                      thetechnobear e.g. you mentioned a different regulator,

                      We now recommend the R-785.0-1.0 . This is a bit quieter than the "E" version that we had in the BOM at the very beginning. I don't think there have been any other changes to the BOM @bela_robert?