arco Posted January 17, 2002 Author Share Posted January 17, 2002 Mobile, You cannot find the link because thesite has since changed its contents. But I discovered I had kept this text in my files. Here it is: Short Question -------------- What is the best biasing for KR 2A3s? Long Version ------------ I have built a pair of Paraglows with KR2A3s. They were built with the "snubbers" circuit either side of the rectifiers and had an extra LC stage (7H & 470uF) to the PSU. The result was a low supply of 380V, 372V at the 2A3s anode and a poor sound (IMHO). I then changed the 2.5k cathode resistor for the 3K one that comes with the kit for use with the standard 2A3s and shorted the additional PSU choke, keeping the additional C. The result was a higher supply of 395V, 377 at the anode, 235V anode-cathode, -39V grid-cathode on the 2A3 and a waay better sound. I am now wondering if by increasing the supply even more the KR 2A3s could be better biased and if so what I should be aiming to get. I have gathered that the "classic" 2A3 bias point is 250V anode-cathode and -45V grid-cathode but as the kit supplies a lower cathode resistor for the KR2A3s (2.5k instead of 3k) I'm presuming the biasing for the KR valves is different, in which case what is it? TIA, Neil (J Mackie). Aristidis www.aca.gr/pop_coumpas.htm Quote Link to comment Share on other sites More sharing options...
JohnR Posted January 17, 2002 Share Posted January 17, 2002 Hi arco, email Gintaras at http://kwtubes.s5.com/, he's a very nice guy. Is there such a thing as a "factory second" tube? I didn't think so... I don't where the above are from, my assumption was from military surplus. Anyway, you can ask him. I have 40 (which I bought before Rozenblit announced his amp, Victor Khomenko favorably suggested this tube for SETs and OTLs on AudioAsylum some time ago and was even kind enough to fax me the data sheet) -- but I haven't tested them yet. The listed price on http://www.tubes.ru is $5.90. ($US?). I thought their's was lower. Anyway, 100 tubes is not too difficult to buy if you can get a group of people interested. I bought, tested, and sorted 120 EL509s for the other OTL. All the best, JohnR Quote Link to comment Share on other sites More sharing options...
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