Postcards from the Bleeding Edge
Friday, August 26, 2005

  Battling Hum...

If you got here from elsewhere, there's some updated information on this digital hash problem described here. Thanks for taking a look at this.

With an upgrade to the fabulous rme-audio multiface and ardour my studio has undergone a major facelift. I'm now trying to quiet all the instruments I have so to get a recording that can take advantage of 24 bits of 96Khz chocolately goodness.

I had some 60hz hum in my guitar interface, and ran a DI box on it to hopefully fix it. It didn't. I put my foot on the box while I'm playing - No more 60hz hum. Something about this guitar is interacting with itself, or I'm just an electrically charged individual, or my whole studio is a conductor or something....

OK, I can live with that fix for now, but the sound coming out of my XV-88 is driving me bats. At about -60db there's this unusual sound (depicted left with the gain boosted up to where you can see it - here's a sample of the sound: 96khz, 44khz) even when the device is idle, no processors on, etc. A balanced line output ought to be giving me -96db or so...



It's a weird sound, with peaks every 2 seconds per channel, each channel offset by a second.... It's not a 60hz hum at all, or even a harmonic of 60hz (I think)... it does have a harmonic on itself, too, with a cycle of about 24-26 seconds or so...

I long ago had just put a noise gate on it, and forgot about it, but I was trying to record a quiet passage without the noise gate late last night and I kept hearing it and I'm thinking that maybe something has given way within the XV-88 amp or processing module - or this is just a flaw of the XV-88's sound generation in general, or some sort of modulator was stuck...

I hear it on headphones if I listen closely, with nothing else plugged in.

I ran a new big fat wire to ground. No change.

I plugged in a electrical noise filtering box. No change.

I ran everything through a UPS. No change.

I unplugged the UPS from the wall. The whole circuit now floats - not connected to ANYTHING. No change!!.

What the heck is it? Now I turn the darn thing on and I'm painfully aware of the sound... help! I see that doc is talking about audiophilia - I'd love to be an audiophile if I can just get rid of my stinking hum... what to try next? running the ups to ground?
Gotta find a tool that will let me look closer at the frequencies than audacity...

Naturally I tried to contact Roland's tech support only to find that their support website was a push only system - no email contact and an email to supportatroland.com bounced... their website didn't have a tech support phone number listed - I finally found one on the back of the Roland manual and got to a support tech who asked the obvious questions and then forwarded the url of my blog to his manager.

I've got an update to where I'm at with debugging this problem here.

Monday I'm just going to take the unit into work and if it still has this noise and Roland tells me it's not normal - it's going into the shop.
 
Comments:
Dear Brenda:

Thank you for your thoughts!

It's not a hum per se' but a digital buzzing sound. I've heard similar noises before from poorly shielded sound cards in PCs, although never at such a constant (if low) volume. I put an parametric EQ at 800HZ with a 24db cut on it and that got rid of the sound nicely - at the expense of quite a lot of real sound...

All the cables in the chain are using gold balanced 1/4 I/O connectors with a couple XLRs as well.

Power to this building is on a long (100 foot or so) electric cable. I'd buy into ed skinner's antenna theory if I hadn't tried this with a standalone ups not tied to power at all. If there was some other device within a few feet that was radiating something but unless it's hidden under the house or being aimed at me by a soviet satelite (joke, joke) I don't know.

I'm otherwise a good 30 feet away from major power lines....

So, anyway, my big test is going to be moving all this gear to an entirely different location and that will be the kicker. In the meantime I'm going to try boosting the gain on this other sound module to see if I get the same noise out of it....

I'm thinking A) I might put some extra shielding inside the roland itself B) break out another device that generates sound to see what it does (I have but it's a -10 db, everything else is +4 - I think - I have to go through
 
Sounds like digital hash coming from the VX-88 itself. The electrolitic caps inside of it might be going south, there might be a broken shield on an internal jumper, etc.

Divide and conquer. Pull back the shield on the cable from the output, and SHORT IT, and see if the noise goes away.

--Mike--
 
Man, its been 3 years since your audiophile problem. You must have forgotten about it already!!
But if youre on the lookout for brands to namedrop, then it cant get better than these 5 big home audio.
audio cables guide
 
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David Täht writes about politics, space, copyright, the internet, audio software, operating systems and surfing.


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