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198.24.6.135
In Reply to: RE: WINGED CS BLOWING UP posted by rr1405 on May 13, 2008 at 12:13:11
I have a very strong suspicion that there's a 'whole lot' of bad power tubes circulating around. Put another way, basically factory 'duds' sold to un-suspecting retailers and ending up in our amps.
Nine years ago, I started to buy power tubes from several sources. I seemed to always have issues with tubes from Parts Express and MCM. But the funny thing was that all RAM Labs tubes 'always' worked flawlessly. From MCM or Parts Express either they were DOA, or develop red plates, popping sounds, etc.
After battling through some Winged-C 6550's and some Sovtek 6550's purchased from so called experts, I decided to buy a quad of tested Chinese KT88's from Upscale Audio.
I paid about $34 each for these Genalex Clones. What I got was a working set of burned-in and tested tubes that have performed flawlessly for the last 3 years . I still have them running in a pair of Dynaclone MK3 DIY Monoblocks at 70 ma each and about 490V on the plates, they don't even break a sweat!
My experience with Russian power tubes over the years has been mixed, especially EL34's. Most EL34's will never work in a real Mullard 5-20 amplifier. The standing bias current on the 5-20 amp is about 1 watt ove the rated limit of plate dissipation on an EL34. I have a complete cemetery of EL34's from the days when I used to play my Mullards and not realize that the great sound these amps gave me was the sound of my tubes dying. And no-one makes a real EL34 nowaday's. Not even close to the Genalex versions or original Tung Sol. My suspicion has to be in the chemicals used today versus 40 years ago. The modern tubes simply don't sound the same as the older NOS types. Modern tubes seem to work best when implemented into new circuitry optimized for their characteristics. I find that new production tubes and vintage electronics is a lottery.
Recently, we re-tubed some M60 MK3 OTL's with 6AS7's from and ebay Ukraine seller with stellar results, once again, by chance only as they were sold as tested. To this date I have not been able to get ANY Winged C 6550 tubes to work in my Dynaclone MK3 amps, but then again I did not buy them from Upscale, RAM or Jim McShane. The duds I have are from MCM and one of the web based "Tube Stores".
A quad of new and tested JJ 7591S tubes almost blew-up my Harman Kardon A700 amp the other day, I was lucky to be in the room at the time. To solve this I used my NOS 7591's sparinglyand some 6GM5's with an adapter.
Good power tubes are not as easy as one may think. And not all sellers test their tubes as thoroughly as others do.
Try a good quad of tested Siemens, etc.
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