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In Reply to: How about using EL519's instead of EL509's? posted by CometCKO on June 13, 2005 at 16:27:03:
I've used my original EL 509's since 1999 with no problems. I use them today and have never replaced any. I've had to switch the tubes side to side on occasion.
These amps are sensitive to bias adjustment. Some are rock steady as to bias and some are not. My amps' bias drifts frequently. If the bias is a small bit off you can hear it. I've added (as have many others) a twenty turn pot with a dial lock to the bias adjustment. If you have frequent bias drift this mod will help keep the bias steady and make the bias easier to adjust. Keeping you bias adjustment within factory spec. will be more beneficial and much cheaper than changing the output tubes.
The deal with the Trancendent Amps is that they are so transparent any deficiency in your system upstream from the amp will be revealed in abject detail downstream.
If you are going to use Transcendent equipment you must unlearn everything you might know about audio reproduction. That is, source is most important and everything downstream from there is of progressively less importance as far as sound quality is concerned. The only exception is since you don't have a load matching transformer between the amps and speakers be sure your speakers don't take any severe impedance dips. (Below 4 ohms.) 16 ohms speakers with OTL's (if you can) are the way to go.
Take the money you were going to spend on output tubes and modifications to the amps to make them work and buy the best sources you can. If you are using weird interconnects and speaker wire sell them too. Spend that money on sources or speakers that maintain impedance. The T8's just don't need modifications. It's not an Atma-Boogie.
Follow Ups:
Oops! I ment ten turn pot and forget the Atma-Boogie comment. It's much too late for me to be on the Internet
The good news is that my bias has been quite stable. But I'm wondering what wandering bias sounds like? I'm not so anal that I'll check the bias frequently, but what are the audible clues that I should look at it?I'm still looking for the ideal speaker match. I've got a set of moderately efficient MTM monitors from North Creek Audio that are nominally 12 ohm speakers and don't dip below 8. What speakers are you using Bob?
Thanks for your advice!
I use the Joseph Audio RM30si with the T8's. Minimum 7 ohms impedance. The brickwall crossover works very well but is somewhat inefficient. I use the RM7si with my SEOTL's and they sound great. Joseph's take forever to break in. (SEAS drivers)
most of what Bob has said is correct. I would only add that if you decide to go with EL519s, you must replace all the EL509s with EL519s. You can't run the two types side-by-side in the same amp.As for difference in sound, I can't comment, since I've never run EL509s. The Ei-branded EL519s certainly sound fine in my system. They are generally reliable--I've only had (1) go bad in the lot of (32) that I bought from Billington in the U.K. over a year ago.
The sound of drifted bias is quite obvious--usually added distortion in the form of a raspy "edge" to the transients in the treble. One of my amps had drited over 1 volt off center last week, but re-centering it cleared it up. BTW, I installed the twenty-turn pots that Bob mentions--can't imagine trying to adjust bias with a typical 270 degree pot!
I reset bias last night with the stock pots, and it's very much hit-or-miss going by the sweet spot in a small fraction of a turn. I'll have to do this soon... but I can't bear to stop listening long enough to do the mod.Thanks for the advice!
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