Last year I switched over from using an older Mackie 32 bus mixer board to a desktop Mackie MCU Pro and a Scarlett 6i6. This allowed a smaller footprint mixing console and enough audio inputs to accommodate two keyboards and a microphone. I wanted to downsize the and modernize the music technology.

Well… shit. The MCU Pro developed this horrible high pitch whine internally. It does not bleed into any internal audio recordings but will definitely be heard if I used my microphone to record acoustic sounds like voice.

I tore it apart and have determined the MIDI input / power supply board is the culprit. Unfortunately the ICA 0726 transformer component I suspect is bad is also an obsolete part. I can’t find the part anywhere.

My only path to fix this annoyance is to purchase a complete board assembly. I’m willing to do this if it is a reasonable cost. The reality is I’m wearing headphones when doing most of my recordings and the whine will not be heard. The issue becomes apparent when I will try to use the microphone and record voice.

I contacted Mackie through email. Hopefully the support team will have a board assembly for sell.

UPDATE: after several attempts of reducing the sound without replacing the transformer I ended up purchasing the entire power supply board. I know for certain the whine noise is coming from this board since I disconnected all other connected PCB’s. The board will be shipped soon.