I have a M1 with distorted audio. So if i take an initialized patch (could be the piano sample or any other pcm sample) with no effect or whatsoever, once a key is played a faint noise is heard in background beside the sample and when the sample reaches the sustain portion, it starts making wierd electronic sounds like ( pjjj, pzzzzz, wiiiii with rather high pitch but the volune is normal or slightly lower than the sample itself) and it goes away once the amp envelop closes.
When loading factory patches, i can almost hear the patches working properly in the background but the noise / distortion is more present and upfront due to the effects sustaining and elongating it.
to me, the distortion looks to be in the digital domain/side, not in the analog side(pre amps,…) , suspecting it’s the DAC…. Any Ideas ???
PS , once i had korg LE with bad pcm memory ROM, i was able to gldiagnose it by loading cutom samples to ram and they played absoultely fine. Also, whenplayjng the distorted pcm rom sample, the efects / filters,.. sounded natural meaning i can hear the impact on the samples being normal, just the source is not good ( like if using a delay on a blip, i can hear it repeated nice and clear). with this M1, i feel the distortion is after the effect because its all blurred and murky.
I used a pre amp to probe back the distortion from the output, the tailing distortion looks like a square wav. I traces it back all the way to the output of the first pre amp after the DAC. The dac op irself is very low so i cant hear it.
I found something very interesting while probing the DAC DIGITAL INPUTS, i was with pin 2 MSB, i was able to hear the actual M1 output audio signal and again after the wave finishes, i can hear and see the trailing square wave.
each of the DAC other Digital input have different variations of the patch audio and has a different distortion spectrum.
important thing to mention is that the training square wave pitch corresponds to the keyboard like a regular patch,
Concur with effects RAM chip - had exact same some years back with an older YAMAHA CLP-301 - crackling farting noise when note faded away - turned off reverb and all good. Replaced reverb RAM chip and all fixed.
With effects ON, i definitely get the squealing noise you’re referring to, that’s confirmed. However, even without effects (m1 initialized), i get the distortion mentioned in my original post. With that being said, bad RAM could definitely be a culprit. I suspect the the trailing distorted my be the looped portion cause i noticed it sounds different depending on the selected waveform
What would be the best way to check the ram chips in place ? Unfortunately i don’t have any chip testers but .
I just noticed the effect act like iir as in they get sustained until changing the patch. That increases the likely hood of the RAM chips being the issue
i captured the M1 output via an audio interface (attached link). captured the factory preloads, initialized patches without effects and initialized patches with effects. notice how the initialized have a buzzing trailing noise.
Note: everything you hear including the white noise is coming from the M1. There is no interference, bad audio cable.
funny thing, when i audio probe the RAM chip(yes😀) IC10 ( data lines DQ1-4), i can hear pretty much hear the M1 main output audio,lol. Same pins on other rams have more white noise but i can hear some audio there.
the keyboard is fixed. One of the 5 ram chips (the one in the middle) was bad. once replaced, the keyboard audio went back to normal.
I think these RAMs are dedicated for the FX IC. Based on the block diagram, the FX chip is the last thing the digital audio passes through before the arriving at the DAC and im assuming even if the FX isn’t applied, the chip had to operate to an extent in order to pass the data hence a corrupted RAM can distort the audio of a clean signal. When applying FX where the chip has to be further involved, the bad RAM impact becomes more announced which was exactly what happening in my case.
I’ve seen how bad PCMs and bad DACs sound. This was definitely different.
