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fiddlefadel
08-17-2008, 02:01 PM
I bought the Blues Jr LTD from GC a couple of months ago and I really like it, however I would like to take some of the treble out of it.

I plugged it into the original P12R in my '59 Deluxe and it sounds pretty similar, considering it needs more breakin time.

I ordered some TAD el 84s from KCA along with a matched triode JJecc83s and tung sol 12ax7 and a ge12ay7. I had some matched JJ el84s already.

When I put the JJ or TAD el84s my amp starts stuturing and making a scratching noise,:( when I replace the original GT el84s everything is good.:AOK
I put the JJs and TAD in other amps and they work perfectly.

I am perplexed, are the replacement tubes that far out of biasing that this would cause the noise? The original GTs have the white lettering indicating medium gain. When I ordered the TADs form KCA I specified medium gain also.

Any Ideas?

thanks
Dave
merkaba22
08-17-2008, 04:55 PM
I put JJ EL84's in mine and it was very nice:)
jbltwin1
08-17-2008, 05:20 PM
Being that new takes worn out tube sockets out of the mix. I guess you could have loose ones though from changing the tubes. They don't exactly put good stuff in these days. I think that I'd ge the bias check with new AND old tubes for a reference and then start putting the tubes in one at a time to see what's changing first. Those are both too good of tubes to BOTH be bad. Mike sells quality stuff to so unless they were damaged in shipment, I would have to start looking elsewhere. Try re-tensioning the tube sockets then. Did you change the preamp tubes also?
fiddlefadel
08-17-2008, 08:24 PM
I have never seen this happen before and I have been dealing with tubes for 40 years. I put the new tubes in another amp and they worked fine so I'm pretty confident that they are ok. I have a reissue tung sol 12ax7 in v1 and it's woking just fine. I tried 2 different pairs of matched jj el84s and they both did the same.
Also the bias on these amps is not easily adjustable, you have to change a resister.
I don't understand why the original tubes work but none of the others don't!:puh
Dave