This is driving me mental! It's only noticeable on higher gain settings at a loud-ish volume...

My guitar is picking up a beeping sound not unlike an ECG machine in a hospital!

I've determined the culprit lead is from my Pod XT Pro's Unbalanced Mono Out going in to my Tascam FW-1884 so I pulled it out and plugged it back in making sure that the audio lead is no way near any other cables but it's still doing it. It definitely seems the beeps coincide with the red HD activity LED on my computer. Would unplugging it do much though? A simple tiny LED surely can't emit that much interference to a quality shielded guitar lead which is a good 3 or 4 feet away from it?

Any ideas please?

* Just a thought... Would there be any disadvantages using an S/PDIF lead? Would that be likely to help? Surely I'm better off keeping everything in the digital domain anyway in my case? I assume my Digital I/O on my Tascam is for S/PDIF? It doesn't say.

Edited by Rhys Llewellyn (12/10/11 02:14 AM)

Hi Rhys!

Once again this sounds suspiciously like a ground loop problem, whose classic symptoms include digital noises that coincide with mouse, hard drive or graphics activity.

Have a read of my sticky thread on the subject and see if it helps:

www.soundonsound.com/forum/showflat.php?Cat=&Number=222392

Fingers crossed!


Martin

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YewTreeMagic

I have a different model from that same general range and the RCA jack is S/PDIF on my unit and works well with a TC M300 effects unit.

If that is your one open input it will cause the problem to go away. If you have other inputs open it may not since you still have the earth connection.

You need to make sure both units sync up. You should be able to set sync on the Tascam to be the S/PDIF input. Make sure your clock rates are set the same. I find if I mismatch 44.1 and 48Khz on my unit it very nearly works! Unless you were listening carefully you could miss the occasional glitch. Then when you play back free running everything is suddenly at a weird pitch. Other than that I have never had a sync problem and I actually sync to ADAT in with the M300 synced to the Tascam's S/PDIF out.

Thanks for the replies.

I first thought it could be a ground loop issue, but I thought those issues only resulted in a general low frequency rumble type sound and it only really applied to laptops.

I've managed to get the Tascam and Pod to sync via S/PDIF but it seems a little unreliable. I still get the occasional glitch so I think I'm just gonna stick to with my original set-up. It could be that I'm just using a Phono lead perhaps?

Anyway, it seems that moving my computer to the other side of my desk has solved the problem... Since I sit at my desk when recording, my guitar was in very close proximity to my computer (about 1 1/2 feet away) which seemed to be causing the interference

Thanks again.

Quote Rhys Llewellyn:

---

Thanks for the replies.

I first thought it could be a ground loop issue, but I thought those issues only resulted in a general low frequency rumble type sound and it only really applied to laptops.

I've managed to get the Tascam and Pod to sync via S/PDIF but it seems a little unreliable. I still get the occasional glitch so I think I'm just gonna stick to with my original set-up. It could be that I'm just using a Phono lead perhaps?

Anyway, it seems that moving my computer to the other side of my desk has solved the problem... Since I sit at my desk when recording, my guitar was in very close proximity to my computer (about 1 1/2 feet away) which seemed to be causing the interference

Thanks again.

---

Phew!

1. In the good old days of analogue only, ground loops generally resulted in mains hum and a little grunge, but now that digital devices are connected you may hear anything from whistles, modem-like noises, hum and other digital noises. For me the clue was that your noises tied in with other digital device activity such as mouse movements, hard drive accesses, graphic redraws and the like, which is fairly typical for a digital ground loop problem.

2. If you're using an S/PDIF connection then you should make sure your phono to phono cable is of the 75 ohm digital variety rather than an audio one, since the latter can result in all sorts of problems ranging from occasional dropouts to no signal getting through at all. Nothing too specialist is required - I've used a £5 video cable from Tandy for years!

3. Airborne interference is a different issue again, characterised by proximity - in other words, if the device picking up the interference is moved further away the problem diminishes, as you've just found. As their name implies, humbucker pickups are far better at rejecting such interference than single coil pickups.

Glad you're sorted though


Martin

--------------------
YewTreeMagic

I thought I'd solved it, but apparently not!

Through my "rigorous" testing, I've since realised that it was my guitar sound, or more specifically, my noise gate "solving" the problem!!

So I'm back to square one, but it now seems it's my Pod XT Pro which is the problem.

Basically, I've recently started getting in to guitar software modelling inside the box and using Cab Impulses since I just can't seem to get a decent tone direct from the Pod.

Anyway, my current configuration is:

Pod XT L Mono Out (Unbalanced) in to channel 1 of my Tascam
Pod XT Unprocessed Out (Unbalanced) in to channel 2 in to the Tascam for re-amping.

It is this Unprocessed Out which seems to be incredibly noisy when I add a high gain amp modeller insert. I usually track with the "wet" Input 1 and record the dry signal in 2.

If I remove the Pod from the equation and plug my guitar directly in to the Tascam and load up an amp modeller, the phantom beeping is not there.

I'm mainly using a PRS Custom 24 w/humbuckers, so I'd like to think it's not the quality of the guitar's electrics.

Hi again Rhys!

Based on that more detailed analysis I think we’re back to digital ground loops

If your Pod XT Pro and Tascam FW-1884 both have earthed power supplies, you’ve certainly got one ground loop by connecting two unbalanced outputs from the Pod to inputs on the Tascam. However, you’ve also said that you only get noise when adding a high gain amp modeller insert, so perhaps that’s the culprit rather than a ground loop (you can check by unplugging the Pod XT L Mono Out - if the noise from the Pod XT unprocessed out then disappears it’s a ground loop issue that you can cure either with a custom lead or a lin-level DI box).


Martin

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YewTreeMagic

Hello Rhys,

Not sure if you've fixed this yet, but I was having a spookily similar issue http://www.soundonsound.com/forum/showflat.php?Cat=&Number=952643& page=0&view=collapsed&sb=5&o=365&fpart=&vc=1#Post952643

I've now fixed this by disabling C1E in my bios. I obviously can't say it'll work for you but if you are as desperate for a fix as I was it's worth a crack.

Aparently lots of Gigabyte boards these days have this issue (it's a feature apparently ) but my board is an Asus and it was the cause....

Good luck

Gary