Hi -
All this input is excellent, thanks so much! I'm clobbered with work during the week, and it's going to take some time, studying these responses. But a couple comments. My cpu with on-board ALC1150 is not horrible, with 110db S/N on front channels, etc. For my ears, it might be sufficient, if I could remove the hum. I HAVE tried many of the things mentioned... but I will try more... The voltage level of the hum signal seems to correspond with the voltage level of the power supply signal needed for the "processor ON" input. Like, .2v. I think there may be some Siemens computers with a new approach, where this signal is not used (and these Siemens MOBO's use ZERO volts to keep the computer OFF, and thus consume no current at all when turned off.) But anyway... I really don't want to have to buy another MOBO. Maybe a pro-sumer audio card would be nice; like everybody, I enjoy buying neat new stuff. :) I like the idea of using the PCIE bus, to minimize latency for my digital piano. But an external (USB) audio interface would introduce less than 1ms latency, and might be a good practical solution.
I will work thru this and let you know the progress... Thanks again!
John
On Mon, Mar 6, 2017 at 11:28 AM, Len Ovens <len@xxxxxxxxxxxxx> wrote:
On Mon, 6 Mar 2017, Bill Purvis wrote:
Not strictly Linux Audio: I've had problems with ground loops in our church PA system.
Been there done that :)
That amp is powered by from a mains socket in the adjacent room and we had very significant
mains hum with it until I interposed an audio transformer. Thus no direct ground connection
between the amp and the rest of the kit.
I have just made it my policy to use an isolation transformer between any two units with power. I have 6 for outputs (board to FOH and monitor) and 3 for inputs (guitar, bass, kb). This is a small setup. The hall has two power entrances and the grounds seems to be at odds. I have made sure the board and the stage use the same power (so a mic holding performer doesn't get buzzed when touching an amp) but one of the FOH speaker/amp units is not... we had one blow before I isolated it. I think it has a transformerless PS so I am not sure if it is related or not... it went back for repair at no cost.
The idea with USB is to have power included, this is great for USB memory sticks and things, but for audio, a USB port that has no power and is optical would be wonderful.
--
Len Ovens
www.ovenwerks.net
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