Amp Head produces Crackles when FX loop pedals on

[keepy]

Hi there,

My HT-20H FX loop when engaged is causing crackles in the sound

This is more evident when driving the amp.

What i've tried:

turning off the pedels in the FX loop - Crackles stop
tried different cables (that I know are ok) Send & Return - Crackles still there (when pedal turned on)
tried different pedels - Crackels still there (when pedal turned on)

This is only an issue when the FX loop has an activated pedal through it, obviously doesnt happen when nothing is even plugged into the Send/Return

anyone got any ideas? or anything else I can try to find the problem?

FX is also set to the +4db.. and I'm driving a 2x12 cab with V30s at 8ohm for the cab - using the 8ohm output on the Head.

Praying for something I can fix myself... but its looking like an AMP tech job at the minute, and I have a recording session on Sunday looks like ther'll be no FX being layed down

I've had the amp a couple of years, power tubes and pre amp tubes replaced last year.

[Dizzyg12]

since it seems to be only when your fx loop is active, my first thought is that you have some dirt/dust in the socket. Get some of that canned air they use for keyboards and blow the gunk out of it.

I just got my HT-60 back from a tech working out some volume/power drops and he fixed the gain selector (voicing) switch on OD2,which was the main problem, but he also found a shorted wiring issue on the fx loop. Mine was evident with our without the loop in play though, so probably not the same issue you're having.

[Markystang]

Have you tried it on the -10db setting? Does it make a difference at all?
I'm with Dizzy. My first thought is dirty jacks too.

[keepy]

Hmm we'll. quick update on this one after a full days recording today..

I blew out the sockets with compressed gas and I thought it had done the job.. Until we ran it to the desk and you could hear clear as day the crackles in the playback. Even in the DI straight to the desk. Even more evident when punching the amp harder.

Less noticeable on the clean channel on more melodic stuff, but still there.

Even tried it without anything running or connected to the effects loop, and you could still hear it So obviously not the effects loop..

Also tried another guitar through it.. Same deal.

Loose tubes perhaps?

Luckily the trusty HT-5, that I had chucked in the car 'just in case' came to the rescue. Just meant I had to DI only instead of DI with a cab mic as well.

HT-5 sounded epic. Such a solid amp. Just at a loss as to what to do with the HT-20, might be time to pay a visit to the amp doctor.

[Hedgehog]

If the crackling only happens when the pedals are turned on then I don't reckon it's an amp problem (at least not directly, like a dodgy socket or effects loop problem - that would cause noise whether the pedals were on or not). I've had a "sizzling/bacon frying" noise (I initially thought was a dodgy power valve) that turned out to be a dirty connection on an effects loop cable, but that happened all the time, regardless of whether a pedal is on or off.

Most pedals are designed to work at instrument signal level (-10dB) rather than line level (+4dB), so if you're running the effects loop at +4 it's probably worth changing it to -10 (although some pedals don't care).

Rob

EDIT:
I've just re-read your last post and noticed you say it's doing it with nothing in the loop now - so all the above may be useless! I'll leave it there though just in case.
One other thing I've had causing noise with my HT20 is power line networking. I've got a couple of "speedplug" network things in my house and the Blackstar seems very prone to picking up noise from those if people are using the web while I'm playing - that makes a similar sort of popping noise. Never noticed it with other amps I've had so it seems to be something that amp is sensitive to.
On the other hand, it could still be a valve problem - pulling them out and reseating them (or even just wiggling them around a bit) wouldn't do any harm and might help if the problem is just a dodgy connection in one of the valve sockets.