Re: Cathode Bias PushPull

On Wed, 23 Apr 2008 12:10:45 +0100, Eeyore
<rabbitsfriendsandrelations@[EMAIL PROTECTED]
> wrote:

>
>
>flipper wrote:
>
>> Eeyore wrote:
>> >flipper wrote:
>> >> Robert Casey wrote:
>> >> >>
>> >> >> Rk = Vbias/(2 x idle)
>> >> >>
>> >> >> Where Vbias is the desired bias voltage and idle is the per tube
idle
>> >> >> current at that bias voltage, with the 2x because there are two
tubes.
>> >> >>
>> >> >
>> >> >A problem is that if one of the pair of the tubes hogs most of the
>> >> >current, which can lead to red plates.
>> >>
>> >> True, but I wonder how often that happens because a single Rk was
>> >> quite commonplace.
>> >
>> >I've seen it in a VOX AC30 for example. FOUR EL84s sharing a single
Rk. I
>> >modified it to use 2 resistors.
>>
>> Well, that's interesting because the original comment was about one
>> per two tubes and that's what you changed it to.
>
>I rather imagined that comment referred to an output stage using 2 tubes
rather
>than four.

Yes, that's what I said and what you changed the 4 to: a pair of
deuces on a common Rk.

>
>Graham