[BC] Gatesway board stuff

[Phil Alexander]

On 27 Oct 2005 at 19:05, Powell E Way III wrote:

> 
> 
> HMMM!
> 
> The Gatesway we had at WKDK had 6BQ5's not 6AQ5's. Getting 10 watts out of a
> pair of 6AQ5s would require a cherry red plate!
> 

Nope! I think the Gates did use 6BQ5's, but I had a PP 6AQ5 circuit that
used about 275 - 325V on the plates with 470 ohm cathode resistors. 
Screens were usually tied to B+ but could get better performance with a 
tapped primary and screens connected to taps. I used either UTC HA or LS 
series transformers for output. Depending on use, I used either a 12AU7 
or 6C4 split load phase inverter. These were used for both line and monitor 
amps up to +40 dBm, although, to be honest, they generally operated at 
quite a bit less because we didn't drive them with that much input.

But then, I also got 70 watts pure sine at about 2.5% distortion from a
pair of 5881's by running them in a true class AB2 with fixed bias, and
both static and dynamic balance controls. Ever see a "tuned" audio amp.
this thing had enough controls to be a transmitter. <g> We used it for
blasting a pair of EV Musicasters at record hops, and I mean blasting.
Those tubes did show some color - dull red spots on the plates. RCA
never intended 5881's to do anything like that.


Phil Alexander, CSRE, AMD
Broadcast Engineering Services and Technology 
(a Div. of Advanced Parts Corporation) 
Ph. (317) 335-2065   FAX (317) 335-9037





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