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jim 30th June 2004 02:41 PM

OTL question.
Hi all,

I've some 6336A tubes and a couple of 190V transformers plus a beefy heater transformer.

Is it possible to adapt the schematic in the link to 6336's without to much trouble ?
Plate voltage will be lower and power also but I don't need that much power.


(schematic comes from A. Ciuffoli's site A. Ciuffoli


fdegrove 1st July 2004 12:37 AM



I've some 6336A tubes and a couple of 190V transformers plus a beefy heater transformer.
My experiences with NOS 6336As are nothing to write home about as far as reliability goes but if you must use them you can adapt the Ciuffoli circuit around them.
The main problem with tubes like this is that there are hardly (none I know of) tube testers that will take them and quite often half of the dual triode is gone without the user knowing it...

Many years ago a friend of mine buit the Taki OTL and I must say it did sound very good:


The 500K plate resistor for the EF86 should be 150K and the value of filter cap for the bias supply is missing. I suppose something around 220F/250V should do.
The value of volctrl on the input can be lowered (1M pots aren't easy to source) to 250K.

As for the Ciuffoli circuit, you'll find some advise in the OTL thread regarding this amp that you may want to consider.

Cheers, ;)

Sch3mat1c 1st July 2004 01:49 AM

1M pots are all over RadioSnack and Mouser. I'd be more afraid of it munching up HF response due to the high impedance. Although not much of a problem with a pentode input (Frank, what's happening to you!!?? :eek: ;) ).


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