need help on transparent sounding 12au7 tubes

Thanks for all the great recommendation, this is good information to know, will certainly use these recommendation down the line. I plan to clean the pins of the RCA's this weekend, should I use Silclear on it (silver enhancer)?

I just listened to my system tonight (well rested and everything)and it sounds amazing. This is my second night with the Eklipse and I'd have to say I'm very happy. This pre is very quiet, sweet, slightly forward in the midrange which bring out vocals perfectly for rock albums such as Dire Straits Brothers in Arms, SuperTramp, etc.

You can't go wrong with RAM Labs Super Low Noise grade. These are very quiet and transparent and only 2% of tested tubes are graded Super Low Noise. The 12AU7 is difficult to find with low microphonics, especially with NOS tubes. I use Super Low Noise RAM tubes in all of my input and power tubes on my VTL and CAT electronics. Here is the website tubeaudiostore.com and I am not affiliated with them other than as a consumer with 30 years in this hobby.

You will have NO problem finding low noise/non-microphonic NOS tubes. You just have to shop with sellers that know how to test for such things. Kevin Deal is one of those that is most fastidious with his testing and grading (http://www.upscaleaudio.com/view_category.asp?cat=44). If, by stating, "transparency", you are saying, "no colorations": then you don't want anything British. They will impart an unnatural warmth to your presentation. Siemens and Telefunken are the most transparent, of which the ECC802S would be the ultimate. They were ECC82's, specially selected for low microphonics/noise, linearity, and triode balance(and cost accordingly). There are no new production tubes that can come close to the reproduction accuracy of a properly selected pair of NOS tubes. The exception to that rule in 9 pin miniatures are the EAT tubes (http://www.musicdirect.com/product/73403). There again- You WILL pay for the quality. They don't manufacture a 12AU7 unfortunately.

I think it's helpful to write in terms of coloration and transparency when
describing characteristics of different tubes. I also believe it's less helpful to
write potentially pejorative statements like "unnatural warmth".
Who is to say what is natural and unnatural, and what one tube may do in one
persons circuit versus another person's circuit?

To describe a tube as being warm/colored in the mids, or rolled of in the
highs is enough to allow someone to make a decision about whether that
tube might be worth investigating.

I'll give an example that happened just yesterday. I acquired a tube preamp
model that I had owned several years ago. My system is completely different
than it was when I owned the preamp previously. The first go-around, I loved
Mullard Blackburn 6922 and 12AU7 tubes in the preamp. I had tried Siemens
CCA (early 60s grey riser) and found them to be too incisive, and frankly too
austere for my taste. Well, yesterday, I decided to install CCa tubes again
(Siemens early 60s grey riser) along with Mullard 12AU7 (early 60s, Blackburn
production). This time around, with my new system, the Siemens CCa were a
very nice change over the Mullard 6922 (early 60s, Mitcham production).

So, my point is that systems and preferences differ, and systems and
preferences change.

What's preferable now, may not be preferable down the road and vice versa.

I'm in favor of describing characteristics of tubes without adding negative
personal opinion that may dissuade someone from experimenting with a tube
that might actually provide the listener with enjoyable results. Transparency
varies by small or large amounts depending on who is evaluating the tube.

Now, I absolutely agree that if the OP seeks transparent 12AU7 tubes, then
Siemens or Telefunken are more transparent than other brands, and
especially the ECC802s model previously mentioned.

It's been my experience, over the years, that any equipment with nine pin Mullard or Brimar tubes installed had an added warmth, sugary glaze or "tubey sound"(as the originator of this thread put it) that simply does not exist in live music. Said coloration was easily eliminated when the tubes were replaced with those of German manufacture. What others may prefer/enjoy/seek in their sound does not concern me, as Scar972 asked about "transparent", "detailed" and "resolving" tubes. I replied based on what I know to be true. Scar972- Kevin Deal at Upscale has a great amount of experience with the tubes that he sells, in a wide variety of components. Call, and ask him for suggestions regarding the presentation you'e seeking.