Vox Ac15 unsual hiss. Pulling my hair out!!!

[elmington]

Hi Guys,

I'm new hear and in dire need of help so I ended up here after some google searching.

I have an issue with my AC15 CC1. Listen to the video, please

http://www.youtube.com/watch?v=beHEcD5pP3Q

There's some unusual hiss, all most sounds like a rattle snake or egg shaker.

It only appears after a few minutes when the amp heats up. One thing I have noticed you can hear some faint creaks like the metal or tubes expanding in heat, not sure if this is normal

Its only when I play on the bridge.

I've tried removing the speaker and chassis from the cab
tried swapping tubes
tried moving the output transformer wires around to see if it was parasitic

Some thing else I've noticed is when I turn the mix of the tremolo circuit up the volume pot is noisy when I move it but not when stationary.

Anyone any ideas,

Kind Regards

[Guus]

Hi Elmington.

listening to the video let me hear some wrong vibrating !!!
Also what you call 'snakerattle' but no realy a hiss?
Could be anything.

I would say a tube failure but you've mentioned you have already swapped the tubes by others, so that eliminates tube failure.

I would take the following steps:

1: first check your guitar. There could be something rattling. Also check at the head of the guitar (vibrating between bone and tuningkey sometimes brings problems);
The strings aren't fresh anymore??

2: Put another guitar in the input of your amp (Or low level radio or CD player) and check. If the problem stays check amp on loose/vibrating parts;

3: If the problem stays bring your amp to an amp techn and explain the problem and let him hear it.

Succes

Regards
Guus

[elmington]

Thanks for getting back,

I'm taking it to a tech tonight. I'd taken the speaker out of the cab and removed the chassis and it was still there. It was mostly happening when playing my jaguar in the bridge position but I'd tried that in my amp at my studio and it was fine, when switching to the neck there was no problem as you can see in the video so ruling out it being the guitar.

Taking it to a tech after work. Im done tinkering with it. Kinda losing with will to live with it lol.

PS I just changed the strings. Put 56-11's on it. You got me wondering about the behind the nut theory

[Phil_S]

Have you tried another speaker?

In the studio, are you saying same guitar, different amp rules out the guitar as the problem? Your statement isn't clear on that point. IOW, maybe you brought your amp to the studio and the amp was OK there. If the latter, it is the location, not the amp.

[elmington]

Sorry yeah I tried the same guitar in a different amp and the noise was not present. Even tried hooking the guitar up to my stereo and it wasn't there. No I haven't tried another speaker. I'm hoping its not the speaker. I bought it a celestion blue off ebay and I hope its not a dud.

I dont think its the speaker though cos the noise does not appear when playing on the bridge pickup and it only appears once the amp has been on a few for a few mintues which would suggest some thing more electrical?

I've put it into flynnamps.com in Glasgow, Scotland

These guys are the best in the country so hopefully should have it sorted. I'll report back with their findings chaps!!

[Phil_S]

It could even be something as simple as that particular guitar mated to that particular speaker. Even though there is nothing wrong with either one, they just don't get along. It happens and it can be very frequency specific. You've got two different coils in the mix -- one at each end of the signal chain. Did you demo the problem to the amp tech and did you leave your guitar at the amp tech? They may need it to duplicate the problem. Well, they would have asked if they wanted you to leave the guitar and chances are they did not want to take your guitar.

[elmington]

Hi Man,

No I didnt leave the guitar but it happens to all my guitars, telecaster(not as apparent), jazzmaster, jaguar and my casino, only in the bridge position.

I did send a link to the youtube video too

PS I'd thought they'd just hook it up to an oscilloscope to see the interference