[Amps] Biasing a Class C modulated final

Roger (K8RI) k8ri at rogerhalstead.com
Tue Feb 17 21:13:31 EST 2015

Not sure the 6L6 would be a good choice due to price, unless you have 
some, or a good source.  The price on them is astronomical.  My guitar 
amp uses 6 of them.  I could purchase a nice, new amp for less than 
replacing those tubes.


Roger (K8RI)

On 2/17/2015 5:14 PM, KA4INM wrote:
>   On 02/17/2015 03:11 PM, Paul KW7Y Baldock wrote:
>> I am building a 2x813 class C final modulated by 2x813.
>> The typical way to bias the class C final is with a combination of fixed
>> bias applied to the control grid and bias derived from the rf drive
>> through a grid resistor.
>> Rather than fixed bias applied to the grid it seems that I could achieve
>> the same effect by using a pseudo zener in series with the cathode,
>> similar to what is used in cathode driven linears.
>> Any thoughts on this approach?
>   I am guessing common cathode RF amplifier, a more standard way to do 
> it would be an adjustable bias supply and a clamp tube on the screen 
> grid.  (6L6 or similar) look into any pre-1960 ARRL hand book.

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