Help with VTL TL 5.5 Preamp

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.

Enjoy!

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.