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Suggestions for 12AU7 & 12AT7 Tubes - VTL 2.5

I have a VTL 2.5 Pre-amplifier. It has 2 x JJ 12AU7 and 2 x ARS 12AT7 tubes. The sound is flat, without a good soundstage / imaging and lacks bass and dynamics.

I would like to know changing which tubes make the most impact in VTL 2.5

(1) Change the 12AU7 / ECC82 tubes
(2) Change the 12AT7 tubes
(3) Change both 12AU7 and 12AT7 tubes

After doing some research on the web, I have come across the following tubes (open to other tubes and to your suggestions) :

12AU7 - Mullard CV4003; Mullard M8136 (NOS); Siemens E82CC
12AT7 - Mullard CV4024; Mullard 6201; Valvo 6201

I am looking for low noise tubes with extended highs (no HF rolloff) that can address the above mentioned issues and improve the sound of my pre-amplifier.
bssk
desmondjim
67 posts
 
I use Mullard CV4024 in the phono section of my VTL TL5.5 and they do exactly what you are looking for. They are anything but flat and and have solid bass.

I would also suggest Sylvania Gold Brand 6201s. I use them in my ST 150 amp and I like them even better than the Mullards. To my ears they are a little fuller in the midrange and have a touch more weight in the bass than the Mullards. But they are not that much better that I feel like I want to buy another pair and replace the Mullards I already have.

Sorry I can't make any informed recommendations for 12AU7s.

Cheers,
Jim
mofimadness's avatar
mofimadness
4,152 posts
 
I used a matched quad of the Mullard CV4003's, (from Upscale Audio) in my Belles preamp and was totally blown away. I had tried numerous others and found these to be excellent.
steve_g
9 posts
 
The VTL 2.5, in stock form, is anything but flat or lacking in dynamics. I would suggest getting a fresh set of stock tubes to use as a point of reference. They should be relatively inexpensive as they are current manufacture tubes.
steuspeed's avatar
steuspeed
501 posts
 
Try Andy at Vintage Tube Services. Not cheap, but the tubes I bought from him were exceptional (Telefunken 12AU7).

http://vintagetubeservices.com/page18a.html
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