[Amps] GS23B Plate load resistance for HF / audio analogy

[Leigh Turner]

Yes, I too prefer the graphical load line design approach. The old RCA tube
publications were great, as were the Mullard/Philips and STC tube guidelines
back in the era when tubes ruled the day; and still do in some applications.

The NOS GS-35B Triode and GS-23B Tetrode are a tremendous bang for the buck;
particularly in amateur UHF amplifier service. 

Leigh
VK5KLT

-----Original Message-----
From: peter chadwick [mailto:g8on at fsmail.net] 
Sent: Friday, 1 November 2013 9:16 AM
To: Leigh Turner; amps at contesting.com
Subject: Re: [Amps] GS23B Plate load resistance for HF / audio analogy

Leigh

Personally, I prefer the load line approach, which is basically what RCA
advise. But, as the old French saying goes, 'each dog to his own vomit'.

73

Peter G3RZP


========================================
 Message Received: Oct 31 2013, 10:36 PM
 From: "Leigh Turner" <invertech at frontierisp.net.au>
 To: amps at contesting.com
 Cc: 
 Subject: Re: [Amps] GS23B Plate load resistance for HF / audio analogy
 
 
 Yes, those numbers are about right Peter.
 
 On that much larger allowable linear plate swing on the tetrode, that
 characteristic and efficiency difference is also evident on my valve HiFi
 amplifier using the "Kinkless Tetrode" KT88 tubes in Ultra-linear P-P. 
 
 When I switch the screens from their normal 43% UL taps on the output
 transformer to "triode" mode by strapping them to the plates, one observes
 the said much lower Po and efficiency...but with a completely different
 distortion in IMD spectrum...that some critical listeners prefer.
 
 Leigh
 VK5KLT
 
 -----Original Message-----
 From: Amps [mailto:amps-bounces at contesting.com] On Behalf Of peter chadwick
 Sent: Friday, 1 November 2013 4:24 AM
 To: TexasRF at aol.com; keepwalking188 at yahoo.com; dezrat1242 at yahoo.com;
 amps at contesting.com
 Subject: Re: [Amps] GS23B Plate load resistance for HF
 
 Assuming 3kV on the plate, 500 volts on the screen and AB1 operation in
 grounded cathode, I calculate a PEP output of 1540 watts, a dissipation of
 1240 watts, efficiency 55% and a load resistance of 1570 ohms - calculation
 method as per RCA.  Peak plate voltage when loaded is 3700 volts.
 
 The 4CX1000A has a much bigger allowable plate swing before the plate
 current curve starts to bend - which helps the efficiency.
 
 73
 
 Peter G3RZP