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Help with VTL TL 5.5 Preamp

I recently acquired a Vacuum Tube Logic TL 5.5 preamp. It utilizes 6 tubes: (2) x 12AX7 and (4) x 12AT7. In trying to get to know this preamp, I've rolled several different combinations of tubes, BUT I cannot get the highs to sound smooth and "sparkly."

The preamp images well, has air and texture, is great sounding in the mid-range, good bass slam, etc., but the highs are driving me a little nut... sharp, edgy and too much grain. The highs can get in your face and blow you back a bit.

I've used various combinations Mullard, Telefunken, Mazda and Brimar. Right now, my set up is: (2) Mullard 12AX7A and (4) Brimar 6060 (T-Logo). All the tubes I've tired have been matched.

Any thoughts, suggestions or experiences?
bside123
mitch2
3,906 posts
 
When I owned this model preamp, the highs were one of the best features so hopefully you get it sorted out.
vegasears
1,173 posts
 
Try the OEM tubes.
ryriken's avatar
ryriken
164 posts
 
Forget the 12au7, try some 5751 tubes in place of the 12ax7, lower gain, maybe you will like them. I own the same pre, use 2 12ax7 Telefunken Smooth Plates and 4 Mullard 12at7 from Upscale Audio. Call him, Kevin Deal, he may know of a tube that can mellow out the pre. Will be trying out some 5751 in place of the 12ax7, the 5751 is a replacement tube for the 12ax7, but YMMV.
bside123 OP
21 posts
 
The amplifiers that I am using are a pair of custom, one of a kind McCormack DNA Mono Blocks upgraded to Ultra Platinum ++.
jylee
306 posts
 
When I had TL-5.5 I did quite a bit of tube rolling. I tried the OEM JJ, Telefunken, Siemens, Philips Mini Watt, JAN GE 5751, and finally found RCA 12AX7. RCA was the most musical sounding tubes with smooth highs. I found Wurlitzer branded RCA tubes that worked wonders. I would look hard to find those RCA tubes. I sold the preamp since then, but still have all the 12AX7 tubes I used with it if you are interested.
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