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Old 18th Jan 2019, 7:28 am   #65
Diabolical Artificer
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Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 7,632
Default Re: 120W PP EL34 amplifier re-born.

Don't know what my EL34's are, Langrex Premium whatever that means, they look well built inside. Another reason I'm reticent about using cathode bias is that I've bought 12 Welwyn 10r W21 resistors to use as sense R's, they cost quite a few bob. Although the amp can do 120w, it will hardly ever do so. as mentioned on recent threads about OP power. At normal listening level it's bunging out about a watt. So I'm a bit like yon numpty's who buy Ferrari's then sit in traffic all day. Still, I take on board your points, 40w per pair is pushing it somewhat.

Not using your OPT's on this amp Joe, using Hammond 1650TA's, 120w max UL, yours will be under run on next amp.


"This brings me to G3 or the suppressor grid....tie it to the raw negative bias voltage" That's an idea.

I know you don't like CCS joe but it gives you better balance, better BW, more OP swing and is adjustable. PS/driver stage at present is ECC99/6H6N paralleled LTP using said CCS, works well. Have ditched the cathode followers.

Havn't done any work on it for a few days, time out as you say is a good idea.

I'd understood about the 500v HT KT88 Andy and other points. the only fancy circuitry in the audio circuit is a CCS, which isn't in the scheme of things that fancy. Good luck with the building work, A.
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