Tempo changing on Meris LXV when I control volume to Strymon Iridum - MC8

I am controlling the volume of my Strymon Iridium with a dunlop expression pedal using the expression out 1 of the MC8. I am also using a Morningstar midi box with separate outs to each midi pedal.

I only have CC messages being sent to the Iridium midi channel, but for some reason the LVX is seeing a tempo change and making a weird tempo change zipper noise when I use the volume pedal. It’s distracting and I’d love help to fix this.


Regarding the zipper noise, it is due to a ground loop from the Iridium’s non-isolated MIDI Input. More info and some solutions here: There is MIDI Noise in my Audio signal

Regarding the tempo change, can you confirm that no CC messages are being sent on the LVX MIDI channel?

Hi James,

Thank you for your reply. I did some research and gathered some examples.

  • It looks like midi persist may be the issue. I always had this enabled (not sure if I needed to??).
  • When I disable midi persist I believe the issue has been resolved.
  • I previously removed the ground from the Iridium midi input to remove midi noise.

Video of Volume Expression impacting LVX midi clock (It did the same thing with my timeline)

Video of Reverb mix Expression impacting midi clock?

Screen Shots of Expression pages in Editor.

This expression pedal changes the Collider reverb mix and decay, but was also causing a tempo change on my LVX (ground is removed on LVX midi cable).

Please let me know If I am missing anything. Is it ok to have midi persist off? Will this cause a negative impact on my setup?

Thanks for the info. Ok I think I understand the issue. If you are using the omniport to send MIDI Clock, the timing may be affected when you are also sending a stream of CC messages out from the omniport. Documented in the manual here: MC8 User Manual (Firmware v3.10)

If you can connect everything out through the DIN MIDI Output then there shouldnt be this issue.

MIDI Clock persist simply disables the MIDI Clock once an event has taken place on the controller (i.e. switch press or expression pedal moving). This shouldnt be an issue to turn off once all your devices are synced to the new MIDI clock tempo, unless you want to constantly sync them to an external MIDI clock source.

Thank You James, I will try connecting the midi DIN to the LXV from the midi DIN out of the midibox.

To make sure we are on the same page, I’m not sure that I’m using the Omniport output for midi clock (that I know of)?? I was just using the Omni out to send CC messages to iridium and Collider.

To clarify, I am currently going MC8 midi DIN OUT to MIDIBOX DIN In, then I am sending 1/8 TRS midi out to my 8 midi pedals (some being converted to 1/4 TRS or DIN).

Can I go midi DIN Out of midi box into LVX to solve the issue?

Thanks for helping me with this one issues, I could not be happier with the MC8 overall. I love it.

Since you mentioned that turning MIDI Clock persist off resolved the issue, then I assumed that the MIDI Clock should be getting sent. Is the MIDI Clock BPM indicator on the MC8 screen blinking? If so then that is an indicator that MIDI clock is being sent. By default, MIDI messages are sent out to all outputs.

Now that you mentioned that you are not using the Omniports for MIDI Outputs, then my earlier post is not relevant. But it does seem like MIDI clock is affecting the tempo on the LVX though - I’m not sure if there’s any issue with it receiving MIDI clock + CC messages at the same time.

Yes, using both the TRS outputs or the DIN MIDI Output will work the same.