suspicious speaker hissing and jumping

[fleabag]

Its my Trace Elliot GP11 Mk 5 4x10 combo, and it only happens to the 1x15 extension speaker, not the 4 combo speakers

Power up with 1x15 TE extension cab attached and there's a big pop and at the same time the 1x15 jumps forward.
Doesn't make any difference if gain and master vol are zeroed or not

Its also very hissy, even with using the graphic, everything above 400hz turned to minus zero and all treble on the bass guitar turned off , still sounds like an angry snake. It seems like it's nothing to do with treble on the TE Graphic, or the bass guitar

The GP11 has a noise switch and i thought it might have stopped working, but when i switched it off the hiss got louder, so its working to some degree

The 1x15 TE cab works fine, but i'm seriously perturbed by the enormous jump ( and pop ) at power on, and the hiss

Maybe the TE 1x15 is just old and needs replacing ?

Edited June 26, 2017 by fleabag

[grandad]

I would have said it's the pop-suppression in the amp, a 10nF across the on/off switch or a NTC thermistor in line. But that would be heard whichever speaker cab is connected. Strange one that. I can't think what it could be. Logically if it only happens with the 15" then that points to the speaker being faulty but what sort of fault within the speaker would cause such a strange symptom I know not. There must be a bright-spark on BC who will know. I'm intigued.

Edited June 27, 2017 by grandad

[gary mac]

Maybe the combo is too heavy to jump forward

[gary mac]

Sorry, wish I had more to offer.

[Norris]

I had the capacitor across the power switch mod done by an amp tech on my old Peavey combo to kill the thump. It worked fine for years until I retired it from service. I can't help with the hiss though

[Phil Starr]

Speakers just don't do anything by themselves. They move because they have an electric signal of some sort. Pop when you turn on is usually a power supply issue and in old amps is often a result of ancient capacitors wandering off spec.though it could be something in their charging circuitry. Most components in amps can produce some sort of white noise which the amp will amplify as some sort of hiss. I can't think of any real reason why it would happen in one speaker and not the other. It may be that the 15 has more bass so the pop is simply louder and more obtrusive and may have a little speaker resonance that makes the hiss more obvious.

Most power supplies store a second or so's worth of energy in the supply caps. so they will go on making sound for a second or so after you turn them off. If you turn off the amp and get a few seconds of 'clean' sound then the power supply is the prime suspect, but it isn't likely to be user fixable unless your electronics is pretty good, there are simply too many possibilities to eliminate. It's off to a tech I'm afraid.

[Happy Jack]

I'd want to know why the speaker is suspicious.

Have you been up to something?

[Beedster]

Sounds like our current PM to be honest

[gary mac]

[quote name='Beedster' timestamp='1498551527' post='3325370']
Sounds like our current PM to be honest
[/quote]

If we must have politics, please keep it in OT Chris

[fleabag]

Ouch

I can try one of my MB New York 8 ohm cabs as an extension and see if that does the same

I sort of guessed it was the amp rather than the 1 x15 extension, but needed to ask

Thanks fellas

[Ghost_Bass]

Have you tried swapping the speakers output? connect the internal cab jack to the extension speaker out and vice versa. To me looks like the problem may be in that extension speaker out jack/filter.

[Norris]

When plugging in the extension cab did you then stand the rest of the rig on top, bringing it closer to your ear line?

[fleabag]

[quote name='Ghost_Bass' timestamp='1498579732' post='3325666']
Have you tried swapping the speakers output? connect the internal cab jack to the extension speaker out and vice versa. To me looks like the problem may be in that extension speaker out jack/filter.
[/quote]

Never thought of that
I'll swap the jacks round and see what happens

[fleabag]

[quote name='Norris' timestamp='1498584541' post='3325711']
When plugging in the extension cab did you then stand the rest of the rig on top, bringing it closer to your ear line?
[/quote]

Its not really feasible to stand a 4x10 combo onto the 1 x15

[fleabag]

I have now swapped the speaker sockets round and plugged the internal jack and extension cable jack in opposite sockets, and the 1x15 still leaps into the air with a loud pop accompanying

What i didnt notice before, presumably because the four 10" drivers are so much smaller, is that they also jump, obviously its no where near as much as the 1x15 and the loud pop is not there.

Also, i tried switching off and then back on again in a few seconds, and this really lessens the speaker jump.

So what is happening there ? I leave it over night and the speakers all jump forward, the 1x15 a lot more than the 4x10, and the 1x15 also pops loudly, where the 4x10 do not

Is there some build up overnight that discharges when turning the amp on ?

[bertbass]

[size=4]The 4x10 and 1x15 are both getting the same thump but the thump is divided between all four speakers in the 4x10 so they all move less.[/size]

[size=4][color=#333333]The cause may be that one side of the amplifier's (presumably) bipolar power supply is rising/falling before the other, causing DC offset at its output -- something like connecting a battery across the speaker's terminals. This is actually very common in solid-state amplifiers, even the more expensive ones. Some include circuitry to delay the connection of the speaker until the amplifier has stabilized.[/color][/size]


[size=4][color=#333333]Your amp doesn't charge up over night, [/color]in fact it's the opposite, the power supply caps discharge. [/size]

[fleabag]

Thanks Terry

So like the poster above , Norris, who had some mod done to his Peavey which was doing something similar , can i get someone
to add a mod to the amp somewhere ? A capacitor across the power switch according to mr Norris ?

[Ghost_Bass]

[quote name='fleabag' timestamp='1498744116' post='3326773']
Thanks Terry

So like the poster above , Norris, who had some mod done to his Peavey which was doing something similar , can i get someone
to add a mod to the amp somewhere ? A capacitor across the power switch according to mr Norris ?
[/quote]

I don't hink you need a mod, your amp should already have a filter to avoid this thump, what you need is to take the amp to a tech for a checkup. I'm not technical but i suspect you have one (or more) capacitors in the poweramp out aproaxing the end of their lifespan. Easy and cheap fix, get it done before you harm the speakers.

[bertbass]

+1

[fleabag]

Thanks guys - i'll see my local tech. He's damn good at this sort of thing