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In Reply to: RE: Here's what I found so far posted by airtime on April 18, 2014 at 16:11:18
LOL
Those tubes should last a 100 years.Call me when you can.
Honest amplification is better than excessive 2nd order distortion anytime.
Follow Ups:
Since airtime seems to have solved the problem, I'll risk hijacking this thread with a question:
I'm measuring -18.5 volts at the grid of OP tubes, pin 2. This is after raising the value (resistance) of the bias supply R from 4.7Kohm to 5.6Kohm. Seems like I should be around -15V?
Also what current in mA should each 7189 draw? Can this be measured (the pair) at the 12ohm cathode resistors?
Peter
(as you can see, i made a little circuit board for the bias supply and phono filament circuit.)
Pete
You did a very nice job and I like your bias supply.I usually keep it at minus 16.5 to minis 18v..Minus 15 is way too low for this amp and the 7189s would be on fire.. Vg2 is higher due to the ultra linear transformer where as wired in pentode, Vg2 would be lowered to about 300v.
Leave it where you have it..This amp will produce about 22wpc with 7189s.
Honest amplification is better than excessive 2nd order distortion anytime.
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