Forum to discuss all matters relating to the MPC1000 and MPC2500 operating systems created by 'JJ' (all versions).
By DustParticle Fri Sep 05, 2025 6:24 pm
I'm currently running JJOS 128XL. I was playing around with the Rhodes samples (e.g. pgm name: Vintage) from the MPC Multisample sample pack from MPC-Stuff.com and noticed MPC's HPF is distorting the Rhodes sample playback, esp. when the note I play is within HPF's transition band. For example:
- When I play the note A2, I can get it to distort badly if I increase HPF's FRQ value to 10 or above, before the note itself being highpassed.
- When I play the note A3, I need to raise HPF's FRQ value to 24 to cause distortion.
That's the reason why I think it might have something to do with the HPF's transition band.
Anyone experiencing similar behaviors?

Also, do you know how to map FRQ (0-100) value to actual cutoff frequencies for MPC1000 / MPC 2500 / JJOS?
By Moot Sun Sep 07, 2025 3:01 am
I've honestly never used the HPF as far as I can remember, the BPF has always been sufficient for cutting the higher end frequencies for me - I sometimes may use the EQ setting to lower the high end a little more though. Worth a try, you may still get the sound required without the distortion!
By DustParticle Mon Sep 08, 2025 4:05 pm
Quick update! I emailed JJOS and exchanged a few emails with Murai-san.
Root cause: some samples with full scale amplitude or normalized to 100% may clip the HPF.
Remedy: Normalize the problematic samples to 50%, or less than 100% in the TRIM page.

Make sure you reduce the amplitude of your samples in the TRIM page (not in the SAMPLE / OUT / TrMIXER page) or it won't work!
By DustParticle Mon Sep 08, 2025 4:10 pm
Moot wrote:I've honestly never used the HPF as far as I can remember, the BPF has always been sufficient for cutting the higher end frequencies for me - I sometimes may use the EQ setting to lower the high end a little more though. Worth a try, you may still get the sound required without the distortion!

I use HPF to manage low freq content and clean up mixes. I've been using EQL in place of HPF.
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By hyena Sun Sep 14, 2025 6:14 pm
really valuable infos. a full on gain staging signal flow diagram would help a lot in understanding how to optimize audio performance in jjos based machines! can you perhaps ask him if he can contribute something like that? thanks!