[Amps] New SB-200 owner

[Peter Chadwick]

Steve said:
>I think they can do better linearity than that - the amps I built have 
all done so at 250-300W/tube. The STC data sheet for 4CX250B gives IMD 
figures under the typical operating conditions. At 2kV, 325W pep output 
they give IMD3 -30dBc and IMD5 -50dBc.<
They can do even better with some negative feedback. The KWS1 (which didn't have feedback) claimed 35dB down, although they don't say if that's relative to PEP or to tone. That's at 1kW input, which would align with Steve's figures.
But you need a screen supply, and from an economy viewpoint, that can be a trouble. If you're building one, you have a stock of 4CX250Bs and bases, and your junkbox has not only garnered its stock over 40+ years, but also has your father's junkbox dating back to 1946, and half your father in laws junkbox incorporated in it (like mine), a well regulated screen supply can cost nothing!
73
Peter G3RZP