SH-1oh1 noise/bleed issues

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    I’m having a couple of issues with my newly installed SH1oh1.

    First, it just seems generally noisy. I’m hearing a lot of “bleed” from the RANDOM waveform in the noise floor of the instrument. Is there anything that can be done about that? It sounds like computer “mouse hashing” or something.

    Also I can’t seem to get the “glide” function to work in the sequencer. Where should I start troubleshooting for that?


    PS: Does anybody know about any plans for software options to control the filter LFO and ENV, etc?



    did you buy your SH-101 recently or a while ago? If the latter, you might try to update the firmware:

    The 101 is pretty noisy as well, please keep that in mind. Does the noise floor change if you change the LFO speed? Does this only happen when RANDOM is selected?

    When correctly installed, glide should work same as in the original. Is the glide switch set to ‘auto’ ?


    OH! I didn’t realize I needed “auto” to be selected in order to get the glide function on the sequencer. Thanks!

    The bleed always sounds like it’s coming from the RANDOM waveform, but I can have the LFO set to any wave form and it will still occur.

    Here’s a link to a short passage. In the release of any of the notes you can clearly hear the “hashing” noise floor, which seems to be some kind of signal coming from the RANDOM waveform. It seems to be present only above 2.6k, so it’s mostly obvious on warm tones and bass tones. That just happens to be what I mostly use my SH101 for.

    (I also included a version of the recording with a 9db boosted high shelf at 2.6k to exaggerate the issues so you can better hear it) … tall-noise

    I’ve had issues with noise in the past, but I don’t recall it being so distracting. I’m pretty sure it wasn’t the random wave form that was bleeding before, though I’d have to re-install the original chip to be sure.

    I’m curious if there’s any options for taming or filtering the noise bleed based on the CPU, as it seems to be effected by which CPU is installed.

    Perhaps someone knows of a way to mod the SH101 to reduce the noise/bleed in general? I’d certainly be very interested in that, even before I got the 1OH1 mod.



    could not listen to your sound demo, it says: “This playlist has no tracks”

    Does the noise floor change if you change the LFO speed?

    did you buy your SH-101 recently or a while ago? If the latter, you might try to update the firmware:


    I purchased the kit this month, so I’m assuming it has the most recent firmware. Maybe I should do an upgrade just to be sure?

    I’ll e-mail you the mp3s of my examples.


    Hi thanks for sending me the samples.

    For me it is hard to tell if this noise is more prominent than with the original CPU. If you can, put the original CPU back in and make a direct comparison.
    Since firmware version 1.03 (which you have), the noise floor is actually lower with the SH-1oh1 CPU (at least on the units we tested).

    In order to get an idea what the source of this noise could be, I really need you to answer my question:

    Does the noise floor change if you change the LFO speed?


    I’ll try to find some time to do the CPU comparisons ASAP.

    To answer your question, no the volume of the noise does not change based on speed, but the characteristic does. Since it’s bleed from the RAND waveform, slowing down the LFO also slows that waveform.

    The noise goes away entirely when I clock the SH1oh1 to external midi and don’t play an external clock. This seems to deactivate the RAND, causing it not to bleed into the post filter path.

    If we can’t find any solution in the future, perhaps just a “mute/kill” option for the RAND would be a reasonable work around??

    I’ll get back to you on the comparison.


    Thanks a lot, this is already very helpful.

    Looking forward for the results of your comparison as this problem as never been reported before.


    Quick update:

    I’ve noticed that with or without the RAND waveform running, that my lowest G, lowest D# and highest G keys all create more noise than any other keys, though some seem to have a little bit of the noise, and some have almost no noise at all (lowest E, and second lowest F are very clean).

    The sound coming from the three most noisy keys almost sound as though I’m getting a high value from the RAND if it were running.


    I just sent you some waves that are comparisons of the original CPU verses the 1oh1.

    It appears that the original CPU also has the problem, and may have a slightly worse noise floor (and possibly also a bit more of the RANDOM waveform “hashing” bleed)

    Looks like the 1oh1 is not the problem. That being said I’d welcome any suggestions to investigate the problem I’m having.



    I did a test comparing my friend’s SH101 (unmodded) to mine, and it seems like the sh1OH1 has made my output signal hotter than his. This could be because I needed to calibrate mine, and his could be out of calibration. I also noticed that his had more post filter “hiss” than mine.

    BUT his doesn’t have the RAND waveform bleed that mine has. I’m looking to take it into a tech to get some opinions.


    and it seems like the sh1OH1 has made my output signal hotter than his.
    That is not possible.

    There are of course variations between different SH-101, some caused by age, other by tolerances.
    Some of these variations can be corrected via calibration, other not.

    btw. your rand waveform bleed could be caused by dirt or grease on the pcb below the sample and hold capacitors of the DAC.
    But no way to tell from here.


    Could the output volume difference be related to his filter not being properly calibrated? Seems like matched settings left his filter more closed than mine.

    I’ll look into the S+H and DAC sections of the board and cleaning it.

    The strangest thing is that the bleed is louder on some notes than others, and those notes are related to the pitch of the oscillator, not the key played.

    Thanks for your help! I love the mod.


    What power supply are you using? Try finding an original BOSS PSA-120 with a transformer.. not the new switching one. Also worth testing on batteries too.

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