another M60 bias question

Posted by ipaforme@gmail.com (A) on May 13, 2012 at 19:13:42

I'll admit I'm completely biased towards my M60 and MP3 audio. OK, now that that is out of the way, I have a question about bias adjustment with say half of the full tube compliment. I am running 6336 output tubes and other mods going back for over 12 years from the days of ASOG. Mark, Paul
and Ralph were always super helpful, along with more guys than I can list.
Lew, Bill, on and on.

My bias was too high with a 4.7k resistor to the bias adjustment POT so I changed it to 10k from Paul and Ralph's recommendation for the 6336's. Now that it is getting so hot I'm planning on running with 4 output tubes per amp, but my bias POT with the 10k resistor is still set all the way low.

Will my mV readings be forced up per plate if I pull half of my output tubes (and with no other adjustment possible at this point)? I'm thinking with no further 'downward' adjustment I'm going to have to up that R value some more to make this viable. Paul already wrote me and and said he added a switch there to be able to toggle between two different resistors to adjust output power on the fly,
so to speak (unless I completely misunderstood him). Pretty cool idea I thought.

Sorry to be so long winded, I've been away from the group for so long.

I told Ralph how I just pulled these amps out of the basement, basically
opened them up, blew them out with some canned air, washed my 6336's and the 12SX7 drivers and powered these guys back up without even the use of a variac and they resumed singing again just like old times.

I have no idea what I was thinking when I let the ex talk me into running
this Denon amp for the surround when we got the new big screen. Maybe that's why she's 'ex'? I couldn't believe the difference when I hooked back up the good stuff....

Absolutely gorgeous sound and the staging is just so much more dramatic it's like night and day.

Thanks for bearing with this overly long post.

Best regards to all the moms out there.

/Mike

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Topic - another M60 bias question - ipaforme@gmail.com 19:13:42 05/13/12 (2)

RE: another M60 bias question - Ralph 09:52:28 05/14/12 (1)

Excellent, thanks again, Ralph! (NT) - ipaforme@gmail.com 11:33:57 05/14/12 (0)

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