Diagnosing USB Host issues when connecting to the Expert SleepersFH-2

Prefacing this with that I am not sure if this is an issue with the HAPAX or the FH-2

For simplicity sake, I had been connecting my FH-2 to the HAPAX directly via the USB host connection on the HAPAX (so USB-C on the FH-2 to USB-A on the HAPAX). My FH-2 is set up with expanders to handle a number of midi channels (multiple monophonic converters, CC->CV, drum triggers, etc).
For the most part it has worked fine, but at a certain point, depending on the “load” of the USB midi connection, I start seeing/hearing dropped gates/triggers (i.e. stuck notes).
I was able to switch the FH-2 to use a standard DIN connection to the HAPAX instead, and that appears to have resolved the issue. I can work with this if needed, but I am hoping to root out the underlying problem.
I don’t think its a loopback issue, as looking at the midi monitor on the HAPAX, there was nothing incoming to it.
Anyone have thoughts/things to try? or anyone else experience this issue themselves?

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I am using it with FH-2 and a few expanders as well, but I set it up differently, USB-B from HAPAX to FH-2’s USB-A. I didn’t detect any issue with dropped messages.
Also (if I understood that correctly) MIDI via USB is supposed to have a much larger bandwidth than via DIN, so it does not seem that your problem comes from data overload.

FH2 was a great companion to the pyramid and seems to be an even better one to hapax. A s someone else mentioned with this particular setup it may be best to go out hapax device into FH2 USBa. It’s always worked well for me and it also gets midi into your eurorack setup for a disting or two. Not to mention your USBc is free to connect to a DAW or configure your FH2.

i’m getting a very similar issue now w/ stuck notes using the FH2 and Hapax. It seems to be worse when I’m connecting USB B on the Hapax to USB A on the FH2. It loses notes of all types somewhat randomly. even with ‘interrupt gate’ set on two midi to CV, i’m getting “dropped” notes. when i connect from USB-C on the FH2 to USB-A on the Hapax(as a host), the problem improves but doesn’t go away. when i toggle the sequence back to the setup with USB-B from Hapax to USB-A on FH2, notes are ‘randomly’ dropped much more again.

this is on a very simple single monophonic sequence using a new ‘blank’ configuration on the FH2 with no MIDI note forwarding of any kind. FH2 is setup relatively simply with only 3 midi to CV converters on base channels 1,3,5. this happens with or without expanders connected to the FH2. i’m stuck right now. cv/gate out on the Hapax is just fine. a Keystep into the FH2 over USB playing back a sequence won’t make it happen.


I’ve experienced similar behavior between the hapax and fh-2. I’m running from hapax usb-a to fh-2 usb-b as well and will get sporadic dropped notes/gates while running a sequence. I haven’t tried running via usb-c, but will give that a shot tomorrow.

I did some more testing of this and I think its something specifically between Hapax and FH2 over USB. I thought the issue had gone away in my case but I can reproduce it with a poly setup. If I send a simple sequence of a few chords, seemingly randomly, a gate get gets held until the next notes play. I’m sending very short notes from Hapax to FH2, so they aren’t overlapping. Here is the part I don’t get: I recorded the same pattern from the Hapax over USB into Ableton and everything looks fine, no held gates. Also when I play the recorded sequence back from Ableton over USB to FH2, there are no held notes. I see the same behavior using USB host or device. Another thing, this doesnt happen if I go Hapax → din midi → usb midi interface → fh2. So something specifically with the USB connection between Hapax and FH2.

Os from expert sleepers said there was a similar issue with the Aruturia Keystep and it turned out to be a bug on the keystep side and they were able to resolve it. I’m wondering if this is something similar.

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My issue ended up being an issue with sending too many CC’s from the Hapax. I was able to reproduce/work around it by adding CCs and reducing their resolution. This was happening over DIN midi as well, but was worse over USB. I filed a bug report with Squarp to see if there is something they can do on the Hapax, to which they replied that they were looking into it.


Thanks for the reply. I can reproduce with no cc, clock, and only 3 pitch cvs and a gate.

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