Hello Steinberg Support or anyone
I have found a reproducible MIDI SysEx transmission issue with my Steinberg UR44C on Windows.
Hardware / software:
- Steinberg UR44C
- UR44C firmware: V3.2.0
- Yamaha Steinberg USB Driver: latest version installed
- Windows
- Bome SendSX 1.40
- Korg M1 synthesizer
Original problem:
I am trying to send a Korg M1 Program SysEx dump through the UR44C MIDI OUT. The dump is 16,350 bytes. The Korg M1 does not receive/acknowledge this dump.
Smaller SysEx messages work correctly. For example:
- 170-byte Korg M1 Program Parameter Dump: works
- 991-byte Korg M1 Global Data Dump: works and the M1 replies with
F0 42 30 19 23 F7(Data Load Completed) - 1,749-byte Korg M1 Sequence Data Dump: works and the M1 replies with Data Load Completed
- 16,350-byte Korg M1 Program Dump: fails; no acknowledgement from the M1
I then removed the Korg M1 completely from the test and performed a physical MIDI loopback test:
UR44C MIDI OUT → standard 5-pin MIDI cable → UR44C MIDI IN
MIDI Thru was disabled. I generated complete single SysEx messages of different sizes and sent them with Bome SendSX while monitoring the UR44C MIDI input.
Results:
- 2,048 bytes: PASS
- 4,096 bytes: PASS
- 8,192 bytes: PASS
- 8,193 bytes: FAIL
- 9,216 bytes: FAIL
- 10,240 bytes: FAIL
- 11,264 bytes: FAIL
- 12,288 bytes: FAIL
- 16,350 bytes: FAIL
I repeated the test with different MIDI cables with the same result.
Most importantly, I tested 8,192 and 8,193 bytes directly against each other:
A single 8,192-byte SysEx message passes through the UR44C correctly. A single 8,193-byte SysEx message does not.
SendSX reports that the complete message was sent in both cases, but for messages above 8,192 bytes nothing is received at the UR44C MIDI IN during the physical loopback test.
I am aware that there was a previously documented UR-C firmware issue involving long (>1024-byte) MIDI/SysEx messages. My UR44C is already running firmware V3.2.0, and I have also updated the Yamaha Steinberg USB Driver, but the problem remains.
Could you please confirm:
- Is there a known 8192-byte maximum SysEx message size in the current UR44C Windows MIDI driver/firmware?
- Is this behaviour expected or a bug?
- Is there a driver/firmware setting or workaround that allows the UR44C to transmit a single SysEx message larger than 8192 bytes?
- If not, could this issue be investigated? Many vintage synthesizers require single SysEx dumps substantially larger than 8192 bytes and cannot accept the data split into independent SysEx messages.
I can provide the exact 8192-byte and 8193-byte SysEx test files if required.
Thank you.
Additional finding:
I also tested the original Korg M1 ALL DATA dump, which is a single 49,791-byte SysEx message.
The UR44C can successfully receive this large SysEx dump from the Korg M1 via its MIDI IN (SendSX receives the data in 1024-byte buffers).
However, when the same 49,791-byte SysEx file is sent in the opposite direction through the UR44C MIDI OUT, SendSX reports “Sent 49791 bytes”, but the Korg M1 does not acknowledge the dump at all.
Therefore the problem appears to be specifically related to long SysEx transmission through the UR44C MIDI OUT, rather than reception through MIDI IN. This is also consistent with my physical UR44C OUT→IN loopback test, where 8192 bytes succeeds but 8193 bytes fails.