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Loud noise from HD500 FX Loop.
by GTLazer on 2013-02-25 02:42:52

I've got a bit of a problem with my weird noise pedal; The Great Destroyer from Dwarfcraft.

I built the pedal from a kit and it's a crazy beast, making all sorts of weird noises but built around the basic premise of a fuzz pedal. One of the side effects of its weirdness is that it has a strange sputtering out noise when the signal level drops; ie after you sustain a note for a few seconds. I figured I could discourage this by putting the pedal in the FX loop of my HD500 at line level. However, the result was not what I expected.

I put the TGD in the loop, switched it on, then filled one of the empty spaces in my patch with the FX Loop. As soon as I did that, there was a constant loud noise from my monitors, even though the FX Loop was switched off. If I take the Loop out of the patch, the noise stops immediately, but with the Loop in the patch, regardless of whether or not it is switched on, the noise is there. If I turn the TGD off, the noise stops immediately.

I fetched my Dad round to have a look, as he's a retired electrical engineer, and we agree that it's not earth-related, as the HD500's ground lift makes no difference (and yes, I'm using XLRs) and there's nothing else plugged into the HD500 other than the TGD, so the whole system has a single earth reference through the TGD's power supply; a brand new Harley Benton Powerplant which currently only powers the TGD. And it can't be signal-related, as it makes the noise with the Loop disengaged.

My Dad reckons it sounds more like an overload kind of noise (he described it as sounding a bit like a chopped square wave), but I've tried the Loop on both Line and Stomp and, while the timbre of the noise changes, it's amplitude does not.

I realise this is (more than likely) a problem with the TGD and not the HD500, but do any of you more electonically-minded folk out there have any idea what process is creating the noise and how/why it is getting into the signal chain, even with the FX Loop switched off? I'm baffled.

Thanks.



Re: Loud noise from HD500 FX Loop.
by jimsreynolds on 2013-02-25 04:56:48

Two three things

First off, check your FX Loop is working ok by patching the FX Send to FX Return and turning the loop on.  If you hear untainted signal then you are probably OK there.


Second thing ....

... some fuzz pedals are very sensitive to the impedance of upstream devices.   They can have a very low input impedance and this can make them unstable.  I am a little surprised if this is the case with the HD Loop but you might eliminate this possibility by placing another pedal (that you know normally works OK in front of the Fuzzbox)  in the loop in front of the fuzzbox.  If this fixes the problem then Impedance may well be the culprit.  

Also, check your FX loop level switch is set to 'stomp' not 'line'.  Wiggle it ... the switch is a little flaky at times.



Re: Loud noise from HD500 FX Loop.
by PaulJam on 2013-02-25 10:39:16

Hi,

The reason you hear the niose even if the loop is off could be the TRAILS setting.

If you have the TRAILS setting in the setup menu set to ON then the return of the loop is always enabled even if the loop is off. This is to allow trails for effects in the loop.



Re: Loud noise from HD500 FX Loop.
by GTLazer on 2013-02-25 14:53:58

Hey Jim,

I've tried 1 and 3. They behave as expected.

Number 2 is definitely a good idea; I've no other pedals in the house at the minute but I'll try it round my mate's house on Friday night and report back. It'll also give me a chance to properly test the power supply as well, which, as such, I'm just assuming is ok as it's brand new and has only been used to power the TGD.

Thanks.



Re: Loud noise from HD500 FX Loop.
by GTLazer on 2013-02-25 14:56:55

Another excellent suggestion. I'll have a tinker with it tomorrow evening and see what happens.



Re: Loud noise from HD500 FX Loop.
by GTLazer on 2013-03-04 01:07:46

First off, +1 to PaulJam. It is the active FX Return that is allowing the noise into the signal chain; makes sense when you think about it, but I've never been a great user of FX Loops before, so it had never occurred to me. I'm pretty sure it's something to do with the HD500 being buffered, but it's the same noise as if I roll my guitar volume off to zero, which has me slightly baffled as I just assumed the volume control is basically just a voltage attenuator.

Anyway, another +1 to jimsreynolds. I tried the TGD behind various pedals at my mate's house with varying results, so it's definitely quite sensitive. Whether it should be or not is still open to debate, as I had some problems with my mate's dead cheap PSU, whereas it was much better behaved with my new PSU, so I'm thinking I might need to test the power filtering cap.

Having said that, the TGD was very noisy through my mate's little Peavey Royal 8; I couldn't get any kind of usably quiet operation. Could be a whole host of things as his living room is ram-packed with all sorts of electrical gear (lots of scope for interference).

So yeah, when I've got a bit of time I'll probably end up taking the TGD to bits again anyway. Either that or I might get a separate set of components and do a build on solderless breadboard so I can A/B between them and see what happens.

Gonna have to build an A/B switch as well. lol




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