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strange tube thang...

P

prof2915

After putting TAD EL84 (Z) in my combo-amp I started having problems with strange noices etc, and to make a rather long story short they eventually fried...

After some research my tech found that they reacted to magnet of my speaker!!??

Although great sounding, these tubes obviously "only" works in amp heads.

Strange:confused:
 

Wakarusa

Member
Messages
1,459
That's a new one. If they don't like the field from the speaker magnet, what's to keep them from suffering in the electromagnetic field of the transformers in a head?

I suspect that there's something else going on here. In order for the speaker to disturb the electron flow in the tube to the point of failure you've got to have one hell of a speaker magnet, the tube operating way out of spec, or a bad tube to start.
 

Reeek

Member
Messages
1,196
Right or wrong, I've had several vintage combos that after I installed a new speaker, one of the tubes would almost rest against the speaker magnet and I never had any issue with bad tone or noise or frying tubes . . .
 

TheAmpNerd

Member
Messages
1,056
Originally posted by prof2915
After putting TAD EL84 (Z) in my combo-amp I started having problems with strange noices etc, and to make a rather long story short they eventually fried...

After some research my tech found that they reacted to magnet of my speaker!!??

Although great sounding, these tubes obviously "only" works in amp heads.

Strange:confused:
I think they
all react in subtle ways. However in your case
I'm just not sure the speaker caused the failure.

If the innards were magnatized and the tubes
weren't built correctly to begin with that would
cause problems indeed.

If you just got the tubes, send em back.
Also, put your old tubes back for a double check.

AND

What else did your tech find?
 
P

prof2915

Originally posted by TheAmpNerd
I think they
all react in subtle ways. However in your case
I'm just not sure the speaker caused the failure.

If the innards were magnatized and the tubes
weren't built correctly to begin with that would
cause problems indeed.

If you just got the tubes, send em back.
Also, put your old tubes back for a double check.

AND

What else did your tech find?
My tech examined the amp and changed the tubes to Russian TAD EL84(M) without charging me anyting :D

He had recommended me the Jugoslavian ones (Z) and felt "guilty" for the failure. (He´s really a wonderful guy!!!)

He´ll get in touch with the TAD and inform the of this strange tube behaviour, and we´ll see what will happen.

He did not find any other strange things going on, and he was VERY puzzled by it all...

My amp - though only beeing played for a short while - now sounds better than ever!
 

TheAmpNerd

Member
Messages
1,056
Originally posted by prof2915
My amp - though only beeing played for a short while - now sounds better than ever!
Keep in mind
the bathtub curve regarding failures.

If something is to fail it typically is at the beginning
or the end of the product/item/cap/tube/resistor/(insert
name here) life cycle.

In my studio days, we just turned everything on
and never (rarely) turned it off. If anything failed
it was typically in the first 30 days.

BONUS

As your new amp breaks in, it will start sounding better and better. Which amp did you acquire by the way?

 
P

prof2915

Originally posted by TheAmpNerd
Which amp did you acquire by the way?

My amp is a Laney VC30.
No Bootheek stuff, but rather nice.
I have a Celestion Vintage 30 in it and use another 1x12 cab (Vintage 30) as well.

Nice tube tones at "not TOO loud" levels.
 




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