Posted by Damir [ 213.202.87.211 ] on August 17, 2006 at 08:45:35:

In Reply to: Re: SE 300B Project, Part 13 - The finished amp posted by horny on August 16, 2006 at 15:43:40:

There`re various red LEDs, and mostly the cheap and simple ones have lower internal resistance (about 4,3 Ohms with 10mA, and U~1,7V - "Valve amplifiers 3" source). This voltage drop depends a little with current through the LED - I suppose that you used CCS with ~11mA, like me? Specs for C3g are Ua=Ug2=220V max., and you are just fine...and probably you used right LEDs, too.
Try to "burn in" your amp a few hours more (a few tens or hundreds h even more desirable:-)) and then decide can you live with this sound like a final version. I`m out of ideas here...you can try various "boutique" cathode resistor(s) bypassed with other types of caps, say 4-5 pcs 22µF MKP in parallel...but for me, red LEDs bias sounds better, and I built the amp (finally) that way - CCS+anode out, g3 on anode, LEDs bias - as I said previously...
Did you try interstage version, too with LEDs bias? (Of course, B1+ must be different, about 200-210V + drop into Rw of ITT).
Of course, please - post us your findings...

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