1. Home
  2. amps-preamps
  3. 1014990563

tube matching in groups or bias

I have a pair of tube monoblocs that take ten el34's for each amp. Each tube can be biased individually. I will soon be to the point that the power tubes need to be replaced. In this situation is buying matched sets of tubes important or will any new el34 tube within the same brand work buy simply adjusting the bias? These tubes are generally cheaper if the matching process is not required, and matching twenty tubes could be quite an expensive process.
bohemian7
albertporter's avatar
albertporter
4,927 posts
 
Almost forgot, I would not buy specially graded or matched tubes, especially new ones. New tubes will be sufficiently close to work fine in your amp.

For used ones, the trans conductance ratings on the advertisers notes should promise at least 80% of their original numbers. In this case as well, that is sufficient.
avguygeorge
2,300 posts
 
Hi, Albert. What 6922's? Is there much dif (beyond price) in the cca? I was tempted to pick up some Sylvania-cca's--Cheep at the price.
albertporter's avatar
albertporter
4,927 posts
 
The Sylvania tube is good from a reliability standpoint, and they are fairly free from microphonics. The reason they are cheap is because they typically do not sound good. This assuming that the Cca designation does not mean they are actually Siemens built for or relabeled by Sylvania.

The best sounding 6922 (6DJ8) is the Telefunken, second is a toss up between Mullard Gold Pin 6922 and the Siemens Cca. Other good choices in this category is the USA Amperex 7308 CEP. This is a military tube with very neutral tonal character and very low distortion.

The tube type sound that I find attractive is not really present in the Amperex. The warmest is the Mullard and Tele, which is probably why they are so sought after and expensive.
More to discover