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Best mellow sounding 12ax7 for Thor TA-1000 preamp

I just bought  Thor TA-1000 and am very impressed with the resolution but want it to be more mellow sounding... Darker and less treble emphasis. Can anyone recommend the most musical but mellow/organic 12ax7 for the Thor? When I bought it the unit has telefunkens. The outputs are already mullards so I am focused on the inputs.

It is feeding vtl mb-185 signature amps and quad esl63 with vandersteen 2wq subs.

Thanks!
montaldo
oddiofyl's avatar
oddiofyl
3,966 posts
 
For modern production jj ecc83s have a darker tone.  I have a pair of vintage RCA 12ax7a that are very smooth, they have good overall balance, not bright but still have good high frequency extention. ...    
hew's avatar
hew
159 posts
 
I have used Full Music 12ax7 in my TA-1000 for last three years and there is not a hint of brightness. They seem to pair well with a pair of cryoed Mullard 6201 that I also use in the unit.
truman
167 posts
 
(RCA "clear tops" generally refer to their 12AU7's, 6201's are a substitute for 12AT7's) ...since the Thor TA-1000 has plenty of gain, I use black plate 5751's with their lower gain in mine. Telefunkens are generally thought to be "brighter" and better for older vintage equipment.

-  As an aside, a knowledgeable friend compared black plate vs. grey plated tubes and could not hear much of a difference. 

noromance's avatar
noromance
9,898 posts
 
Ha. Knowledgeable friend he have cloth ears! All tubes have their own unique sound. E.g. Sylvania 5751 Gold with grey plates sound a world away from GE black plates. I second JJS for a warmer darker sound. You will lose detail over the Teles  though.
jbrrp1
423 posts
 
Yeah, I was a bit surprised by "no difference between black plate vs. grey plate", too.  I hear very clear differences between Sylvania black plates and grey plates; same thing for GE black plates and grey plates.

For the preamp adjustment the OP is addressing, I would think 5751 RCA Black Plate triple micas would be a nice fit.  I find them to be richer, but still have good enough detail and extension.
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