Demeter Mighty Minnie TGA-1-180D

[sunshine_bassman]

My tech partner and I have been trying to get to the bottom of a speaker jack issue, wondering if anyone here had any helpful advice.
Whenever the speaker jack is touched with our bare hands, the sound cuts out with a small clicking sound. It doesn’t cut out when touched with tools.
Now, whenever we took the speaker jacks out of the chassis and let them float freely, the sound doesn’t cut out if touched with anything at all.
My partner thinks that it’s parasitic oscillation or a capacitance issue, not a grounding issue. Nothing seems to be touching or shorting the wires or jacks inside the chassis.

[alexradium]

is it a bridged output amp?
in that case the load is not grounded,you have 2 amp outputs connected to the jack,i guess if you ground it somehow a protection cuts out the whole thing.

[Jazz P Bass]

The output section is of the Class D type.

Why are you touching the jack?

[lowell]

Tech pardner chiming in.

It has the ICEPOWER module. The output goes into protection/shutdown when the SHIELD of the speaker cable plug is touched. This happens with speaker jacks IN AND OUT of the chassis.

You can hear the amp cycling if you leave your finger on it.

Yes we can tell the customer to stop reaching back there on gigs and fingering his plug while he's playing the solo to Beat It... but is there any mod or fix for this?

[Jazz P Bass]

If the amp is configured in bridge mode, that may explain the oddity.

The speaker shield is then half of the output.

If so, the amp is detecting a 'short'.

[g1]

This happens with speaker jacks IN AND OUT of the chassis.

In the first post, he said it did not happen if the jacks were floating from the chassis?

[lowell]

He misspoke

Happens in and out of chassis

[g1]

Thanks. Then I won't recommend insulating washers.

[lowell]

Yup thanks.. they're plastic jacks anyways

[The Dude]

If the amp is configured in bridge mode, that may explain the oddity.

The speaker shield is then half of the output.

If so, the amp is detecting a 'short'.

^^^^^^ That. If they are running the amp in bridge mode, neither speaker + or - is ground and neither will like being grounded.

[OlRokr]

I had the same problem, though the amp sounded fine. Repairman in Florida said it needed new board but he put in the wrong one, a 50w/50w stereo board. This amp takes a 170w mono board. In the process, he removed all the quick connects and soldered the connections. Do yourself a favor and send it directly to Demeter for repairs. I'm $350 in the hole for the "fix" in Florida and neither of the amps he worked on work properly. Both lawyers I spoke with said I'd wind up spendiing more than the trouble would be worth suing for damages. Demeter has mine now and should be done with it soon, I hope. Don't trust anyone with this amp unless they have prior experience with them and know exactly what they are doing! It's a great amp and I miss mine every time I gig. By the way, the board is $118.00 direct from Icepower in Denmark. I was charged $150 for the wrong board that had obviously been pulled from a used amp he had in the shop.

[J M Fahey]

Just curious, what would the "Repairman in Florida" name be?

[Tone Meister]

Call James Demeter and he'll advise best course of action.

[glebert]

I've found ICEPOWER modules to be somewhat sensitive to any load that looks like a capacitor.

[J M Fahey]

And in any case, speaker out jack "ground" is not ground at all but *hot 2", just out of phase with "hot 1" and just as dangerous or unadvisable to touch, like on any amp.

I touch the Hot line with my bare fingers while repairing an amp, it usually oscillates like crazy.

Not even need for a Class D type, humble Class AB ones also make happy oscillators.

Is this "broken" and needs "fixing"?

Well, yes, actual fix is to tell dumb Tech (me) to stop touching the speaker out hot wire, period.
And remembering bridged amps have TWO hot out wires.