[SteveFord]

A little while ago I took delivery of a new (to me) AVAStar preamp.
I plugged it into the 20.7 system and the results weren't too stellar. 
It just did not sound right at all but perhaps it would fare better with Magnepan 1.7s.
It sounded better but there was just too much bass for me and it sounded "off" compared to my Sonic Frontiers SFL-2 which it had replaced.
An anonymous donor (AVNerdguy) sent out a pair of RCA black plates to try and they showed up today. 
After work I let everything warm up, put Zappa's Apostrophe on the turntable and listened for a few minutes. 
Ugh!  Not good at all.  It sounded recessed, bass heavy and fuzzy.
I shut off the preamp, stuck in the RCAs, gave them a few minutes and success!!!
This preamp now has the great dynamics and soundstage plus the tonal balance is perfect from top to bottom.
Those ElectroHarmonix tubes made it sound like I had a wet towel wrapped around my head but no longer.
As a torture test, I put on Fripp and Eno's No Pussyfooting as there's one bass note on Stormtroopers in Stillettos which can drill a hole in your head if the bass is off.
It passed splendidly.
If you own one of these preamps, track down some NOS (not used and beat) RCAs and give them a whirl. 
I wasn't sure how much tube rolling would do for this piece but it made a world of difference.
Frank and his team have designed a tremendous preamp which is just waiting for the right tubes to come along.
Two tubes later and this preamp is as good as anything I've ever heard, no fooling.

[medium jim]

Steve:

Nice, I have a pair of RCA Cleartop 6FQ7's in my Pre as well, and they're great sounding tubes!

Jim

[SteveFord]

That they are, I'm very impressed. 
The 1.7s never sounded better.

[medium jim]

The EH must have been very dark and veiled.

Jim

[SteveFord]

In my systems and to my ears that's an accurate assessment. 
I was all set to get some adaptors and go with 6SN7s but the search is over which is always a good thing.

[medium jim]

In my systems and to my ears that's an accurate assessment. 
I was all set to get some adaptors and go with 6SN7s but the search is over which is always a good thing.

Steve:

Get a spare pair while the prices are still reasonable on them.  I bought a quad of them a few years ago for $60.00!

Jim

[SteveFord]

AVNerdguy surmised that my EH tubes may have been beat but I think it's I just stumbled across the winning combination with all of the crap upstairs, it all just came together. 
I have to think of the preamp thread that was on this Circle a while back and the preamp really is the heart of the system. 
Mr. Van Alstine built a winner.

[SteveFord]

A little more experimentation was in order.
Some GEs showed up today along with some Sylvanias.
The GEs were okay, the RCA clear tops were okay, the Sylvanias are keepers.
Less bass, great mids and highs and a taller soundstage. 
Perseverance pays off.

[Freo-1]

Sylvania made some fine tubes, and are under appreciated in the audio community.  Just as well, because NOS tubes are already too costly.   

[medium jim]

Sylvania made some fine tubes, and are under appreciated in the audio community.  Just as well, because NOS tubes are already too costly.   

Some are and some are still under the radar....The biggest payoff tone wise is to me the front end tubes, especially in the preamplification stages.  Heck, I've had the same Vintage tubes in my CDP for about 5 years and they haven't checked lower on my tube tester.  They made them to last in the day.

It really is a case of cost and enjoyment factor...however, sometimes the NOS can actually be less when you factor the expected life span.  A typical NOS tube will last 2 to 3 times longer than current production tubes....this is a generalization and your actual mileage may vary!

Jim

[trackball02]

I got a pair of GE NOS on ebay over a year ago, they sounded fine in my AVAstar,  but over several months, I noticed increasing background noise (hiss). I replaced with RCA NOS Clear Tops, the noise when away and they sound great.

I guess it is buyer beware. Are there any tube tests which would indicate a low noise tube?

I would like to try the Sylvanias. What is a reliable source for these tubes?

[SteveFord]

I just ordered a spare set from this fellow:

http://stores.ebay.com/VIVA-TUBES/_i.html?_nkw=6cg7&submit=Search&_sid=30442602

[medium jim]

I just ordered a spare set from this fellow:

http://stores.ebay.com/VIVA-TUBES/_i.html?_nkw=6cg7&submit=Search&_sid=30442602

I just bought a quad of NIB/NOS RCA's from 1960.  Here's the mystery, the seller only photo'd the box flaps to show the production date and not the tubes.  1960 is right on the cusp of being either Black Plate Chrome Tops or Grey Plate Clear Tops.

I'm hoping for the Black Plates.  Either way, I will keep a pair and sell the other pair.  I will need to get them in hand before I know what the pair I'm selling will be priced at.

Jim

[trackball02]

Steve, Thanks for the tip on VIVA Tubes on ebay. I think I'll pick up a pair of the Sylvanias.

[medium jim]

Steve, Thanks for the tip on VIVA Tubes on ebay. I think I'll pick up a pair of the Sylvanias.

Agreed, always good to have another go to tube person on the short list.   

Jim

[trebejo]

I got a pair of GE NOS on ebay over a year ago, they sounded fine in my AVAstar,  but over several months, I noticed increasing background noise (hiss). I replaced with RCA NOS Clear Tops, the noise when away and they sound great.

I guess it is buyer beware. Are there any tube tests which would indicate a low noise tube?

I noticed the same thing with the NOS 6cg7 RCA's that I tried. One was hissy right from the start, others got hissy after a few months. The Mazdas and EHs did not have that problem. There was something I liked about the RCA's sound but not nearly enough to compensate for the noise.

Maybe on another system it wouldn't be so obvious, but with high-sensitivity speakers...