#1
Hello,
I wonder if any of you learn-ed whizzos can help me out?

I recently purchased a 2nd hand Mesa Boogie Dual Rectifier and brand new matching 4 x 12 cab.

Every now and then, even without have a lead in the input socket, I have been getting a hissing sort of sound...(a bit like a taxi radio interference/ bleedover sound where it it picked up on the tv or a radio etc)...but there is no voice...it is just like a hiss/signal......the hiss is sporadic and doesnt follow any regular pattern or time sequence.....(it sounds a bit like someone frying chips!) ha ha ha
the noise last for sometimes 2-3 seconds...and other times it has lasted for approx 30 seconds!

I am sure it is not supposed to be making that kinda noise....

This is my 1st valve amp and am a bit new to this.....and I dont wanna look like a dumb turd by taking it back to the store...just incase it could be easily remedied! lol

I am in the UK and am running a 240v version Rec (not a 110v version with transformer)
I have tried using different extension leads and a different wall socket to see if the noise can be "rectified"...but no luck as yet!

The Rec originally came with 6L6's and I have recenlty had them changed for EL34's
but the noise has still been present with both types of valve.

Is it a pre-amp valve problem?

Could it be the 12AX7's?

I would welcome any help!

cheerz for your time!

Dal
#2
its a jack problem on the amp

if the noise happens lift the jack upwards pulling the cord tight

if that does stop it, its an easy fix u just have to tighten the inside part cause its just has came lose over time
#3
Hello!
cheerz for that...I shall give it a go!
tonight during band I have been picking up a radio station too!
am getting pretty miffed with it all now...but will check the input jack socket n let you know how I get on!
cheerz for the reply too!
regards
Dal
: )
#4
hmmm...didn't think of the input jack as being the culprit but I could see that happening.

While I was reading I thinking microphonic tubes perhaps or tubes picking up a radio signal or other interference (which does happen) but I see you've replaced them. Can you validate they were biased correctly and all of that?

Just throwin stuff out there.
#5
Quote by 311ZOSOVHJH
Can you validate they were biased correctly and all of that?

Mesas can't be biased, just flip a switch on the ones that have them


Sounds like preamp tubes to me, are you running your guitar straight into it?
Quote by Dave_Mc
I've had tube amps for a while now, but never actually had any go down on me
Quote by jj1565
maybe you're not saying the right things? an amp likes to know you care.





www.SanctityStudios.com
#6
Hello guys....cheerz for the responses......
okies...I have looked at the input jack socket...and all is tight and no loose wires in sight........i couldnt even get a slight turn on the surface mount nut ....so I am assuming all is good with that.

As for the biasing...yes, there is a toggle to set the bias for the 6L6's or EL34's.
This was set according to the valves that were in the amp.
The sound was still present with both sets of valves. I have now had the valves changed back to the original 6L6's and the sound is still present.

I have replaced/swapped over each of the pre-amp valves one at a time with a brand new 12ax7.....and the sound is still happening.........

It is more confusing when there is nothing plugged into the amp apart from the power lead and the two speaker leads to the cab...and it still makes the noises!!!: (

I have had nothing plugged into the amp....and it makes the noises......
I have run the guitar straight into the amp and it still does the same.......
I have unplugged all the leads one at a time and then plugged them back in again....
still the noise happens.....I have tried unplugging them all one at a time...them not plugging them in...the noise still happens.....

now...something else that is strange..........i usually run a pedal snake system from my amp to my boss floor pedal case using the send and return for effects and the others for power and the main signal.
when i touch the outside of the 'snake' or tap it...you can hear it throught the amp...(like tapping the end of a mic to see if its on)...and the same with a special-made guitar lead.........but when I use an older lead..(slightly cheaper quality)...it does not have that same noise when you swish the lead about or if you tap the lead....it is silent! how bizarre!?!?

I am kinda suspecting there may be an earthing problem with the amp???
does this sound about right?

The amp is still under warranty....but only really wanted to take it back once i was sure it wasnt a 'guitarist' error! ha ha ha

Soz to be a bit of a dingbat guys....but its my 1st valve amp...and I am sure that it isnt sposed to be making any noises apart from sparkly clean or mean n growly!
ha ha ha

cheerz again for all your replies...

it is much appreciated

regards

Dal
#7
Quote by Dal007

I am kinda suspecting there may be an earthing problem with the amp???
does this sound about right?
it is much appreciated

regards

Dal

That is very plausible. Have you tried a different power outlet as well?

On the older lead cable issue - that would make sense if the cable has been twisted a lot and a joint was severed or damaged.

Matrix- thanks for correcting me.
#8
I wonder if it could be some other electronic device near your amp that is causing it. If I keep my blackberry too close to my amp, I get a helicopter type noise right through my speakers when it searches out for signal. Very annoying....
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