User Manual

68 Appendix B: Troubleshooting and Support Dave Smith Instruments
If there is a ground hum in the audio output:
• USB can cause ground loops, so try to resolve any grounding issues
between the computer and the OB-6. Or use MIDI, which is opto-isolated.
If the OB-6 is behaving erratically.
• This is almost always caused by a MIDI data loop. Make sure that any
MIDI Thru functionality is turned off on the MIDI interface/hardware
or in the MIDI software application. Disconnect all the OB-6’s MIDI
connections—MIDI and USB cables—and see if the problem persists.
You can also monitor the MIDI trafc with MIDI Monitor (Mac OS) or
MIDI-OX (Windows) to see if the OB-6 is being overrun with dupli-
cate messages.
If the OB-6 doesn’t seem to respond to its controls:
• Make sure Local Control is on in the Global settings.
If MIDI System Exclusive data is not transmitted/received:
• Make sure that the MIDI SysEx setting in the Global settings is set to
usb or midi depending on which you are using to transmit or receive
MIDI messages.
If the OB-6 plays out of tune:
• Check Transpose and Master Tune parameters in the Global settings. If
they seem correct, you may need to retune the oscillators. See “Cali-
brating the Prophet-6” on page 56. If this doesn’t help, recalibrate
the pitch and mod wheels. “Calibrating the Pitch and Mod Wheels” on
page 57.
If the pitch or mod wheel doesn’t go go full range:
• Recalibrate the pitch and mod wheels. See “Calibrating the Pitch and
Mod Wheels” on page 57.
If the lter sounds strange or out of tune:
• You may need to retune the lters. See “Calibrating the Prophet-6” on
page 56.
If the OS Fails to Load Correctly When You Update:
• The OB-6 is equipped with a MIDI bootloader, which will allow you
to reload the OS in the event the you accidentally “brick” your synth
(permanently freeze it) while updating its OS.