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A higher level than Mullard in tube quality?

I am just getting started in tube rolling which I find pretty exciting. Any thoughts or comments would be appreciated.

I have been upgrading the pre-amp tubes in a DK Design Mark II intergrated amp. My speakers are modded Magnepan 3.6's. My source is a Resolution Audio Opus 21. I listen to mostly acoustic jazz and vocals.

I went from a set of Electro-harmonix 6922 (like $20 each) to used 6dj8 Amprex "Bugle Boy" ($40 each) and that was a nice improvement -- well worth the cost. I just upgraded to Mullard 6922 NOS ($90 each) and WOW! I am amazed at the improvement. I could not have imagine that I could improve a $10,000 rig so much for so little. Now I am thinking ... what's next? Can I spend $300 and get another step up?

At this point, what is my next level up? Or is it more sideways to different type of sounds?

Question: used tubes of the same vintage are significantly less than NOS. Is there any down side to buying used (but tested) tubes? I can get 2 for the price of one NOS and probably get more hours from 2 combined. Also, it seems like a good way to lower the cost of testing different types of tubes ... or ... does the aging change the sound.

Question: I have Mullard Blackburn plant made 6922/E88CC gold pins in GE label from the 1960's. Would I get a different sound if I bought different Mullards, such as from a different time or a different plant? And do I just have to take the dealers word for the details -- it all seems so vague.

Right now I have $300 burning a hole in my pocket to try the next step up. But I fear I may hit the diminishing return ...

Thanks for your comments
mcmanus
whart's avatar
whart
1,930 posts
 
I had Mullard gold pins (NOS) in my Steelhead, but swapped them out for Telefunken 6922s (NOS). Sound went from warm and darkish to neutral and not edgy. A big improvement in my system, given my taste, although not inexpensive.
viiu
34 posts
 
I always thought that Philips SQ 7308 were the best of this bunch and they go for around $200-300 on eBay. I've had the best luck buying from sellers who use good testers and post the results.

Be sure to ask first that the tubes are not noisy or microphonic and what the return policy is.
mcfarland
356 posts
 
Different brands and vintages of tubes have a different (not necessarily better) sonic signature. Mullards are "warm", Telefunkens are "neutural", etc., etc. Obviously you like the warm sound of a NOS Mullard. Learn your tube codes (i.e., the Blackburn plant will have a "b" followed by a date code and usually an xf1 or xf2 on the tube). You do well to invest in a quality tube tester (find them through antique radio clubs, retired tv/radio guys, etc.). A warning though: KNOW who your buying from. I have purchased several "NOS" tubes that supposedly tested well only to find them with shorts, grid leaks, or nearly totally worn out. Usually when I present the seller with the test results they take them back or make good on the deal, but if I didn't have a tester, then what? Andy Bowman at Vintage Tube Services is reputable. Member JSautter is also reputable, as is Brent Jesse Recording, just to name a few. Good Luck and Happy Listening.
dekay's avatar
dekay
2,959 posts
 
Just a note...

XF1 & XF2 codes have nothing to do with Mullard 6922's.

XF1/XF2/XF3/XF4 codes were used on different versions of the EL34 tube (a portion of which were manufactured in the Mullard Blackburn plant, as well as plants in Holland/Japan & perhaps other locations).
jalapenos
81 posts
 
that $300 could go toward a pair of US made Amperex orange label 7308s, or even the white labels. Each will give you some of the midrange warmth of the Mullards, but with more air at the top end and a sharper soundstage.

I personally think it would be just fine to buy used tubes (especially 6DJ8 family tubes which have 10k hour life) as long as it was from a reputable seller as has been already mentioned here. You will certainly save a ton of money if nothing else.
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