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Mysterious D180 effects loop issues

Posted: Sun Apr 27, 2014 11:28 pm
by morgan138
My trusty D180 has been doing a thing where low notes (Eb, D) at high volumes will sometimes make it crackle loudly. I'm thinking it's probably something a little loose somewhere, so I've been poking around.

Which leads me to: the rear effects loop. When I plug a patch cable into this, the amp stops crackling BUT the signal also gets quieter and much thinner - and that's with the effects loop theoretically turned down all the way. If I then turn the loop up (remember, there's nothing in the loop but a 3 inch patch cable), it gets even more quiet and kind of muffled.

It may also be worth mentioning that with nothing plugged into that loop, if I turn it up it the amp sounds more and more quiet and muffled, but never cuts out altogether.

Do any experienced D180-ers have any idea what may be going on? I've had this amp for a few years but have never used the loop before. Thanks!

Re: Mysterious D180 effects loop issues

Posted: Sat Oct 04, 2014 11:09 am
by soundguruman
morgan138 wrote:My trusty D180 has been doing a thing where low notes (Eb, D) at high volumes will sometimes make it crackle loudly. I'm thinking it's probably something a little loose somewhere, so I've been poking around.

Which leads me to: the rear effects loop. When I plug a patch cable into this, the amp stops crackling BUT the signal also gets quieter and much thinner - and that's with the effects loop theoretically turned down all the way. If I then turn the loop up (remember, there's nothing in the loop but a 3 inch patch cable), it gets even more quiet and kind of muffled.

It may also be worth mentioning that with nothing plugged into that loop, if I turn it up it the amp sounds more and more quiet and muffled, but never cuts out altogether.

Do any experienced D180-ers have any idea what may be going on? I've had this amp for a few years but have never used the loop before. Thanks!
The switch contacts at the effects loop jacks have failed. That's the crackle sound.
Replace the jacks or clean the switch contacts in the jacks.
That type of jack fails pretty often. So, I use CLIFF UK jacks instead.

Muffled Sound in the loop:
Typically it's a failed FET transistor.
The FET is used to mute the effects loop, at certain times.
Removing the FET solves the problem. Does not really need the FET to work, at all.
So, many people just cut the part out completely.

No schematic that I can find. So, you will just need to trace through and find the bad FET, usually.