Hi. Running GP5 on a Mac mini. Input is 5-pin MIDI from one 88- and one 61-key controller. Output is through two Focusrite 2i2 devices configured as an aggregate device, thence to conventional amplifiers.
Problem: On startup, there is a significant amount of hum in my audio, to the point it’s unusable. What’s a bit odd is that the noise level changes with what’s displayed on the monitor! (It’s mini-DP to VGA, for the record.) I have tried isolating all devices from each other and cables. I have completely disconnected the monitor. I have tried different audio output devices. I have checked for ground loops, as odd as that may sound. I have tried everything I can possibly imagine, and I’m a pretty imaginative guy.
Has anyone else ever experienced this type of thing? If you have I’d like to hear how you addressed it. Thanks!
Hope you don’t mind getting suggestions that sound too obvious.
Have you reduced the system down to minimum peripherals and one audio interface only? Have you completely unplugged the Keyboards (midi and power?) Have you tried different USB and audio cables? Can you plug the amps into a different outlet?
If all this didn’t help, it sounds like a typical situation when you need a DI box or some other sort of electrical separation of the audio signal, maybe also with ground lift.
To get you right: This is independent of whether Gig Performer is running or not, correct?
To answer your question, Gig Performer seems to be the only cause of the audio interference. On startup, the whole audio signal chain is quiet until I start an instance of GP5. What is, or isn’t plugged in or unplugged — whether it be a cable, something to or from the Mac mini, either or both 2i2 interfaces, or each other seems to have no effect on the problem. Different Mac ports, same issue (even though in a digital world, analog interference shouldn’t be a concern). In addition, I normally use the balanced outputs from the 2i2 boxes; changing to a powered or unpowered DI box from any of the Mac built-in audio (3,5mm), 2i2 headphone out, 2i2 balanced out, plugging the output audio amps (or standalone speakers; tried those too) into a completely different circuit … all have no effect.
My guess is it’s a ground loop hum from a source you didn’t know was possible before and can’t control now because it’s being enabled by something outside your control.
You can spend a lot of time trying to find the (sudden new) source of a ground loop hum, especially if:
any single component in your setup was not manufactured with proper 3-prong AC connectors, AND
assuming there is nothing else connected on the same side of the AC supply transformer causing that ground loop AND
assuming you can actually get control over it, AND
assuming it didn’t crop up as a result of a new venue you’ve just plugged in to, OR
you can hop over to a local PA shop or just order a passive isolation transformer(s) like this, (it’s cheap) and any additional cabling needed
And proceed to completely forget about ground loop hums forevermore since ground loop hums just won’t be able to make it through the isolation transformer in your setup any more.
These are good suggestions - I’d try them all.
I’d still like to have a look at the software side.
Drivers
I remember a similar problem from a couple of weeks ago here, also related to Focusrite. I’m that case it was the drivers that messed things up. Unfortunately, I cannot find the thread at the moment.
Clocking
The aggregate devices may not be properly clocked (sample rate) and synced. Does the problem exist if you select another audio interface directly in Gig Performer?
** Buffers**
What sample rate and buffer size have you set?
Is the noise also there with an empty gig or only with your gig file?
Can you “see” the noise in the input and output indicators on the bottom of the Gig Performer window?
Just another test: 1 focusrite, amplifiers not connected to the audiointerface or the computer (completely isolate them from the mac) and a headphone in the headphone output of the focusrite interface. Use an empty gig in gp.
Another one: same as the above, but also bypass the aggregate device setup and use the interface directly from gp
If that works as intended, connect (in gp) the input channels directly to the output channels and test again.
(This is just to try to diagnose the problem, of course).
GP just uses the default macOS to communicate with your audio driver. By itself it does not make any sound. Are you seeing anything in the output meters? In this image, if audio was being generated inside GP, the outputs would be indicating it, such as in this image.
A faulty driver, or some other misconfiguration, might cause such an issue.
I don’t suppose you’re directly connecting an audio input to an audio output via Gig Performer.
Many thanks to the hive mind — the problem is resolved!
Having tried all these suggestions and getting no obvious result, I dug even deeper and started disassembling component parts. When I opened the Mac mini case, I found a 1/4” long strand of wire that had somehow got between two ground points. Removed it, and no more godawful noise.
Ground loop indeed, in a strange place I’d not have thought to look. The varying nature and lack of 60Hz component threw me completely.
Moral of the story here is: Listen to your fellow users, and don’t discount anything.
. Any port in a storm!
