This sounds like an electronic noise. A preamp with the gain way too hot or too cheap, a laptop powersupply, internal soundcard etc...

Please describe your setup in detail, it will help evaluate what's going on.

Many thanks for the response. So here we go -

The chain that specifically brought this to my attention yesterday was -

*Single coil bass guitar > Whirlwind DI > CAPI VP28 that is in a Radial Six Pack 500 chassis > via db25 into a Lynx Aurora which is connected via Thunderbolt to my PC.

*I find that the sound exists more in Presonus Studio 1.

*The sound lowers in pitch as I raise the buffer size.

*It also seems to want to follow my CAPI VP28 no matter where I place it in the chassis. It still appears on the other preamps, but seems to come more through the bass guitar or microphone signal that is plugged in as it changes in volume when I move the bass to and from the PC tower.

*The CAPI is the same exact sound even with no mic cable or DI plugged in and is steady.

*The sound also starts to diminish if I wiggle around the Radial six pack power cable end where it connects to the chassis.

*It also gets twice as loud if I disconnect the XLR that is on channel 8 input of the chassis, but not input 7.

*The sound also gets interrupted for a split second if I unplug or plug in a totally unrelated USB device. Hard drive, keyboard etc.

*Reaper exhibits close to none of this noise

*Pro Tools exhibits the noise but less of it - this makes me think the CPU activity or coding is involved.

I find all this a bit strange. So it seems that the noise is coming from the PC, but for some reason the radial is picking it up?

I would like to see if its the chassis itself but I will need to buy a db25 breakout(or borrow one) to bypass the Radial chassis altogether as it's my only way in and out of the Lynx currently.

Possible ground loop? In need of power conditioning? I may also try the Ebtech Hum X again - I used to have one for my old PC and it seemed to help.

achase4u, post: 451896, member: 37933 wrote: *The sound lowers in pitch as I raise the buffer size.

:eek:

achase4u, post: 451896, member: 37933 wrote: It still appears on the other preamps, but seems to come more through the bass guitar or microphone signal that is plugged in as it changes in volume when I move the bass to and from the PC tower.

That could be your bass pickup receiving RF interferences. I also have noises when I'm to close to my gear with one of my basses and electric guitar.
When I turn around and point the neck to a certain point (monitor woofer) the noise nearly disapeer.
I got the habit of recording guitars and bass away from my computer for that reason.

achase4u, post: 451896, member: 37933 wrote: *It also gets twice as loud if I disconnect the XLR that is on channel 8 input of the chassis, but not input 7.

:cautious: gotta wait for Boswell on this one...

Ugh - there is definitely a ground issue somewhere and I'll have to find it. Now I can't record a guitar amplifier. If I put the sm57 close to the amp, the hum is almost as loud as the amp speaker itself. Now what suddenly went awry? I suppose I should swap out the power strip that is on the same outlet as the recording equipment and see if a new one doesnt hum... then look at the furman m8x?

This is so odd. I suppose it could still be a fault in the Radial Chassis or its switching PSU(shudder) since that chassis is responsible for grounds, correct?

pcrecord, post: 451911, member: 46460 wrote: :eek:

That could be your bass pickup receiving RF interferences. I also have noises when I'm to close to my gear with one of my basses and electric guitar.
When I turn around and point the neck to a certain point (monitor woofer) the noise nearly disapeer.
I got the habit of recording guitars and bass away from my computer for that reason.

:cautious: gotta wait for Boswell on this one...

Well, in regards to the bass pickup interference, I indeed have dealt with that to a degree in a small room with the pc for years. It actually seems like a clue, because even with nothing plugged in I get that noise in the radial racked gear. So, it makes me think that it's susceptible to the interference in a way that it wasn't before. And furthermore, my monitoring path exhibits no noise on playback of older DAW material or websites, youtube etc - and it's going straight from the Lynx digital out to a Mytek DAC... not touching the radial rack. So this makes me think its the radial. Also, I had a reamp of theirs that did the same thing and have heard from others regarding some grounding issues. I would think if this were in the mains wiring or a power strip or something that it would shoot through even the audio I was playing back...

Hmmmmmm...

It sounds like EMI. Double check everything, unplug every device and plug it one by one and see when the EMI starts. It works this way believe me.

I'd guess that because it's consistent and harmonic rich, it's an oscillating switch mode power supply somewhere that's being propagated by the cabling. It could be generated internally in the computer and is using the USB cabling to get out into the real world. It is extremely low in level, but normalising it makes the whine very easy to hear. I'd personally discount RFI because of the consistency - RFI tends to change as people move and interact. In fact there are plenty of noise sources internally, but most exhibit the characteristic sound of data being transferred, this one doesn't. It's not any of the usual things - so something unstable and harmonic laden is the source.

This looks very much like conducted EMI. Apart from significant 60 and 180Hz, there is a peak at 1378Hz and then peaks at around 690Hz intervals above this. I suspect these are aliaised frequencies from a much higher frequency interference source being conducted through the ground connections.

A consistent variation with buffer size is unusual, and may point to the source of the problem being the PC.