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Old 1st June 2007, 01:24 PM   #1
JandG is offline JandG  United States
diyAudio Member
Join Date: Jan 2005
Location: Washington State
Default op-points for 27 pre...?

I am asking for help in playing w/ differant op-points on my 27 pre. Mine has external PS slightly differant than schematic, but still retaining OA3's & running @ about 90v on plates. I have other glow reg tubes & parts to change things. The signal section is exactly as schematic except for running .47uf cap for now. I would like to try differant op-points & also wonder how to figure the battery bias for the changes. I am running 2 -AA NiMH's per 27 now. Also is it correct to run + to K & - to ground..? The Tung-Sol spec sheet shows a max of 275v plate & 90v Heater/Cathode voltage. I have a Lab grad dual output DC VIX supply that goes from 0-20v @ 2amps, & all variable if needed for anything. I bought that to experiment with DHT's, 26 & so on. Also the Tung=SOL spec sheet shows nothing higher than 11k plate resistance for the 27, why is there a 22k resistor on the plate..?Thanks for your help..

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