Post by sparepart on May 12, 2018 23:27:06 GMT
So I'm trying to eliminate a (very) faint 60Hz hum leaking into the audio....
I finally tracked it down to the 1/8" trs connection on the PC sound card. There is measurable differential between the shields on the TRS connector and jack. Ended up using a scope to see it, but its there and was audible during quiet recording.
Off to the junk box and pulled out a pair of Bogen WMT-1 transformers, and the soldering iron. 30 minutes later, the hum is gone, and the sound card even seems to sound better (might be that it's now working into the correct load Z, and the desk is seeing 600 Ω )
Even if you buy the Bogen WMT-1 new, they are less than 1/2 the cost of the comparable commercial kit. Next step it to mount them on a blank 1U rack panel and add a few mix 43 ferrites for RF/EMI suppression.
I finally tracked it down to the 1/8" trs connection on the PC sound card. There is measurable differential between the shields on the TRS connector and jack. Ended up using a scope to see it, but its there and was audible during quiet recording.
Off to the junk box and pulled out a pair of Bogen WMT-1 transformers, and the soldering iron. 30 minutes later, the hum is gone, and the sound card even seems to sound better (might be that it's now working into the correct load Z, and the desk is seeing 600 Ω )
Even if you buy the Bogen WMT-1 new, they are less than 1/2 the cost of the comparable commercial kit. Next step it to mount them on a blank 1U rack panel and add a few mix 43 ferrites for RF/EMI suppression.
