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In Reply to: RE: 813 verses 4e27 who has tried both? posted by amnesiac on December 15, 2014 at 04:49:58
I have tried both, but only in triode-wired SE mode - in that setup, I preferred the 4E27.Based upon memory, op point was approx 750 vpk @ 125 mA into an 8k OPT.
Edits: 12/15/14Follow Ups:
Jim I think 120ma is to much dc for my trans.I just found these points that I think you posted on it in DIY audio. I am guessing my outputs being finemet 7k cores might be critical of bias currents. They are not the biggest cores. Below are the points that Member Ja2dhc modeled. What do you think?
Ep=700V
Ip=100mA
Vg=-110V
Rl=5KohmI dont need lots of power. I think I only have 3 4e27's so far. They are getting expensive. And the 813 are still cheap. I have 4 by 4-125's too.
Edits: 12/16/14
Beofre thinking you have three, test them. Wire them up as zero bias triodes, light the cathode and apply voltage. If you don't get 200 mA by about 310 volts they are tired. They also may be gassy. I think I threw out about 2 cubic feet of gassy or otherwise bad 4E27's while I was gathering up supplies for my amps.
Said amps are PP, U-L and run 590V on a and g2 with a 10k a-a load with 115 mA idle per tube. given the OP, it is easy to see that they are running full Class A.
The amps are currently running 813's and are awaiting upgrade of the front end to an LTP of EL84's. Balanced XLR inputs.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
Those are the curves I used - have fun.
Thanks
:)
Somebody did it. Not one to let you baby play with.
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