Eliminating mic hum with balanced cables

[Frink]

I'm just starting to bring my old 'bedroom' studio up to scratch - starting with eliminating as much buzz and hum as I can from the mic chain.

I have this chain for vocals and mic'd up instruments:
Mic (Rode NT3 or Shure SM58) into JoeMeek Pre-Amp with an XLR
JoeMeek into an Alesis EQ
EQ into DBX Compressor
Compressor into PC

I was a bit of a newbie/clueless hobbyist when I started, so I used a Normalled Unbalanced Patchbay connected with basic TS 1/4in jack cables.
I got a lot of buzz, but as my hobby was quite low-key, I managed to eliminate it using some VST plug-ins on my DAW.

Now that I'm getting a new PC and some new equipment, I've replaced the patchbay with a balanced unit and have replaced all the cables with sturdy TRS 1/4in balanced cables.
This, perhaps not unexpectedly, has made a big difference to the mic hum/interference.

The problem is now that I'm becoming obsessed with using unbalanced gear - so I have a couple of questions:

My new PC will use a MOTU M2 interface which IS balanced, so I have no problem there.
But I also have another PC that I use for regular work so I will route this into the main amp for everything.
This other PC has a simple single mini-jack stereo output, so to connect it to the patchbay and amp, I would use a splitter that converts the stereo mini-jack into two 1/4in jack outputs into which I can put regular cables.
The splitter/adaptor takes the stereo line and splits into 2 mono lines which means that the connector does not have TRS connections so, I guess, that makes it unbalanced.

Question: Will this matter? i.e. if I have this unbalanced device connected to my amp, will it create interference on the mic even though its not in the recording chain?
If not, then problem solved - I'll carry on as is.
But if this unbalanced section of my setup does cause interference, how would I convert a stereo mini-output into two single TRS balanced outputs to the amp?

Thanks for listening and maybe for answering - it's much appreciated.

Frink.

 

[rob aylestone]

Connecting a computer 3.5mm stereo out to two jacks is almost guaranteed to be trouble free on a mac, and likely to hum and buzz on a PC - just the way it seems to work with PC audio. Unbalancing a balanced input rarely makes much difference, but people spend lots of time making latops buzz free - A DI box is a great way of providing isolation, but you can buy. This gizmo solves the problem. It's British, but I am sure you can find similar in your location.

adaptor

 

[Frink]

Connecting a computer 3.5mm stereo out to two jacks is almost guaranteed to be trouble free on a mac, and likely to hum and buzz on a PC - just the way it seems to work with PC audio. Unbalancing a balanced input rarely makes much difference, but people spend lots of time making latops buzz free - A DI box is a great way of providing isolation, but you can buy. This gizmo solves the problem. It's British, but I am sure you can find similar in your location.

adaptor

Many thanks Rob - I am based in the UK so if you have a particular gizmo in mind, I'm all ears

 

[PitchTempoAndriy]

The work PC can introduce a ground-loop path through the amp/patchbay even though you are not recording its audio, but an unbalanced connection does not automatically mean a noisy recording.

Before buying anything, compare the same short mic recording with the work PC's audio cable connected and then disconnected at the amp/patchbay. Keep the mic gain, routing and other connections unchanged, with noise-removal plugins bypassed for the comparison. Turn playback down before reconnecting. If the recorded hum does not change, that cable is not presently causing the mic problem.

The mini-jack's TRS carries left/right/common; splitting it to two TS plugs is the normal stereo breakout. Swapping those plugs for TRS cannot create two balanced outputs. If that particular connection is the culprit, the audio isolation approach Rob suggested addresses the ground path. His word "adaptor" above is already a clickable link.

Sound Devices explains why this depends on the complete connection path:

https://support.sounddevices.com/hc/en-us/articles/44134251967259-Tackling-Ground-Loop-Audio-Noise