[Amps] Why Heathkit and others floated the grids

[R L Measures]

On Jul 21, 2006, at 8:33 PM, Tom W8JI wrote:

>>            One thread that I have taken from this bilious
>> discussion is
>> that some of you do not realize that most of the
>> commercially built Amateur
>> triode linear amplifiers throughout the 70's, 80's, and
>> 90's have floating
>> grids, of one sort, or another.  It is time to pull the
>> heads out of the
>> sand and realize this.
>
> Being involved in the design process for Heath and others I
> can tell you exactly why Heath and others floated the grids.

Mr. Rauch -- Were you part of Heath's SB-220 design team?
>
> They did so because Bill Orr placed huge amounts of pressure
> on manufacturers to include what he called "negative
> feedback".  If you look at his Handbooks, you'll find a
> circuit called a "super cathode driven amplifier".
>
> The entire concept was seriously flawed,

Indeed.  After spending much time discussing amplifiers with Orr and  
asking questions, an amplifier-builder friend concluded that Orr was  
not very savvy about the subject.

... ...

R L MEASURES, AG6K. 805-386-3734
r at somis.org