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?
What amplifier you use?
It might be worthwhile trying 12AU7 in place of the 12AX7 . It has less Gain , but should smooth ot the Highs .
When I owned this model preamp, the highs were one of the best features so hopefully you get it sorted out.
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.
The amplifiers that I am using are a pair of custom, one of a kind McCormack DNA Mono Blocks upgraded to Ultra Platinum ++.
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.
Bside123, below is a recent ( 12/10 ) email from Steve regarding the VTL 5.5 mating with his DNA Amps.

Hello James -

Thank you very much for your kind words - I am very pleased to hear that you are enjoying your McCormack amplifiers!

The VTL 5.5 looks like an excellent preamp and should mate well with your DNA amps. It has both balanced XLR and single-ended RCA outputs so it will drive either amp, or both at the same time if you wish. Its output impedance is very low (under 200 Ohms) so it is a perfect match for both amps. The one potential problem I can see has to do with its high gain (20dB) and "conventional" volume control. In truth I am not certain exactly what volume control is in the 5.5, but it seems to be a rotary potentiometer (motor-driven for remote-control). If so, you may find your system volume going up quickly as you turn the volume knob. This is not a performance or sound quality issue, but you may find that you are only able to use the first 1/3 or 1/2 of the control's rotation, and it may not track perfectly at very low volume (the L-R balance could be off slightly). I mention this because of your comment about adjusting the volume with your Nuforce preamp. Still, the only way to be sure is to try it, and my guess is that it will work fine and sound great.

For future reference, if volume control is an important issue for you, try to find a preamp with a high-resolution volume control - one with 70 - 100 steps (or more) and .5dB (or less) of adjustment per step. This will solve the volume adjustment issue.


Happy Holidays,

Steve McCormack

I hope this helps in regards to the pre/amp synergy......
Jd_df: Thanks for forwarding the email from Steve McCormack.

I'd never really doubted that the McCormack amps would provide a synergy problem. The particular McCormack amps I am using are extremely revealing, so moreover, I've been wondering about the high frequencies in the preamp itself.

A few people have written to me suggesting RCA 12AX7 tubes. In light of all of the tube variations that have been suggested, I guess I'll have to continue to experiment until I find the right combo. The Brimar quad as well as the Mazda quad of tubes I've tried are renowned for being both airy and smooth.

Maybe this preamp is not be my cup of tea, but I am not throwing in the towel as of yet. My overall sense is that this is a fine preamp, so I'll keep working with it a bit longer. It is definitely way different sounding than a older Conrad Johnson PV-12 that I have in another system. I've rolled the tubes in that preamp, and it sounds very sweet, and than again it sounds very "Conrad Johnson."

Thanks to others for their responses.
Perhaps the sharp and edge treble that you hear may be coming from another component, maybe from your source. I've never felt the sound of VTL to be harsh. I've also owned Conrad Johnson preamp before, and I agree VTL is probably polar opposite of CJ. I found the sound of CJ to be rather dull and uninvolving, while VTL sounded bright and dynamic. If you liked CJ preamp trying to get VTL to sound like it may not be the best approach.
Jylee: Thanks for your thoughts. Those same thoughts haven't passed me by as well.

As far as the CJ goes, I simply like it... kind of a nostalgic or sentimental thing. I am very aware of its limitations, even after some upgrading. Still I like it.

No, I don't want to make the VTL sound like the CJ, and even though I said I like the CJ, I have actually been considering replacing it with the VTL in that particular system... if I can get the VTL to where I like the highs.

I've compared the VTL 5.5 to: Conrad Johnson PV-12, Eastern Electric Electric MiniMax Linestage modified & upgraded by Tom Tutay and McCormack MLD upgraded by SMc Audio to Ultra Platinum.

The sources have included: Nottingham TT w/Clearaudio Maestro Wood Cartridge, VPI HW-19 MKIV (modified) with Transfiguration Phoenix MC cartridge, Ayre CX7eMP CDP, Eastern Electric MiniMax CDP, finally Computer Based Music (Mac) through a dB Audio Labs Tranquility Signature Edition DAC.

Still I get the same results in the highend of the VTL... oh speakers have been: Dunlavy Towers, Acoustic Zen Adagio and DeVore Gibbon III (upgraded). Janis and Fritz Speakers Subwoofers.

What am I missing?

I do hope you find resolution to that which you seek!!!
I tried the 5.5 and gave up it. It was two grainy/noisey for my ears.

In regard to your DAC source (the Tranquility SE) and the treble trouble, have you solved that as yet, and if so, how?

When I read your posting and this thread, I wondered two things:

What USB cable were you using for the DAC? I've had excellent success with the Ridge Street Audio Alethias to conquer a similar situation (just my experience, no endorsement).

I also wondered what power cable you were using with the DAC. Again, my experience: I've found that different power cables affect treble troubles differently, some with greater success than others. These things are system dependent, for sure, so you'd have to experiment here. I've found that the Morrow Audio MAP3 to be excellent and a significant "runner-up" to the Morrow to be the Synergistic Research T3 power cord.

In addition, another variable affecting treble quality is whether the DAC power cord is run through a power conditioner or not. I've noticed this affects the performance of the DAC in the treble range very much.

My experience is with the basic Tranquility model, not the SE, so the variables I've listed here might apply more or less depending...!

Hope my experience helps,

:) listening,

Istanbulu Ed: Thanks for your suggestions. I've got great cables throughout my various systems. I know the sound of those cables very well. For the Tranquility SE DAC, I am using dB Audio's own Essential Cable, but I am certain that the cable and the DAC are NOT the source of my high frequency grudges. I've tried the VTL 5.5 in 3 different systems and have toggled between Analog, CDP as well as the DAC. I have changed configurations, etc. I am certain that I have narrowed down the sound of my complaint to the preamp itself. I am hoping to find a better tube combination and not to just "tame" the high-end with a cable. Anyway, sound is subjective. Many, I am sure, would disagree with me. Again, thanks for chiming in.
I currently use a VTL TL5.5 with a McCormack DNA 125 while my ST-150 is in for service :( I have had great results with the old American Made Tung Sol 12ax7s. The highs were extended and sparkly but not etched or forward. They integrated very well with the glorious mids these tubes had. I also have had good results with the new issue Mullard 12AX7. I didn't like Telefunkens I tried.

On I side note looking at Steve McCormack's email above I do have the gain issues he wrote of. It is especially apparent using the mc phono input that I feel has excessive gain.

Get a Classe CA200 or 300 - much smoother than DNA without giving up bass or resolution. Or just replace the 5.5 with a 2.5 which uses smoother 12AU7 tube.