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Tube Rolling Woes

I recently took delivery of my first tube preamp. Schiit Freya+. It came with new production Tung Sol 6SN7GTBs. I'm running fully balanced from my source components right through to the power amp. My first impression was wow! What an improved soundstage with width and a 3D quality that I've read about. What surprised me is how quiet the system is. I had expected tubes to be noisy. But the Freya+ running with the new Tung Sols is dead quiet. The openness and air in the presentation is tremendous. However, from a voicing perspective, the top end is bright, and the mids and bass are very thin. I have about 75 hours on the system. Ive read and listened to almost every review on this model and no one has complained about the tonal balance. I left an email with Schiit just to make sure that I haven't done something wrong, but haven't heard back yet. 

I thought I'd experiment with some NOS and used vintage tubes. I've purchased from established, well respected vendors as well as folks with excellent feedback ratings on eBay. Of the 8 tubes I've purchased - claimed as tested matched quads (1) or pairs (2) - all but 2 have been either prohibitively noisy, or just didn't pass a clean signal. From my (admittedly small) sample, there has been no quality differences between the well-respected companies selling NOS tubes vs. people selling used stuff on eBay. The good tubes I've received were used tubes (RCA) sold by an eBay vendor. 

So I'm running out of patience. If I go with new production tubes that a vendor will have tested, matched and stand behind the quality, how do I know what to buy? Note that this is a $900 preamp. So, there are limits to what is practical in terms of price point. I can't justify spending more than $200 on replacement tubes. My concern is that even if I spend this kind of money, how do I know what the results will be? 

Any advice is appreciated.

Glen 

128x128spacecadet65
avanti1960
1,500 posts
 
recently swapping tubes on a 6SN7 based preamp, my first one.  i ran into some similar noise and quality issues and have learned some lessons.  
*the older tubes have had the most issues regardless of noise testing or where purchased.  the oldest tubes i buy now are late 50s.  
*brent jessee has a "bang it" procedure that is supposed to help by shaking loose internal debris.  it worked on one out of 4 tubes but might be worth trying,  the procedure is on his site.  
*always buy from someone with a clear return policy.  there are some very reputable sellers on ebay fyi that i have had great luck with.  


lowrider57's avatar
lowrider57
5,417 posts
 
Noise testing is a must. I have many 1940’s WWII 6SN7GT/VT-231. These are cream of the crop tubes with no noise, they present a black background. They were purchased from Vintage Tube Services and from Brent Jessee.
Andy has told me he tests many tubes to find one that is quiet.

spacecadet65's avatar
spacecadet65 OP
58 posts
 
Thanks for the tips on the contact cleaner and alcohol. It's alway interesting to find that old technologies like WWII tubes have survived the test of time! I'll check out the Bang It method from Jessee and see how that works. I have nothing to lose from these noisy tubes at this point.

G
wolf_garcia
6,726 posts
 
I also have a first gen Freya and a fave feature with this preamp (and the "+" version) is the fact than you can instantly check the "honesty" of your tubes...I often switch the thing to the passive or FET settings (adjusting for the large gain drop relative to the tube setting) to compare to the tube sound, which instantly tells me what I need to know. The micro detail, punch, and general tonal "rightness" of the tubes always wins, but if the tubes were funky somehow (microphonic, exploding, dead) or wearing out I'd hear it. Note I prefer NOS GEs but have Sylvania Chrome Domes, new Tung Sols, JJs,  and others in reserve. None are noisy.
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