Peter Chadwick wrote:
> 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.
It needn't be. If you stay simple, a dropper from the anode supply with
an uncomplicated active shunt regulator costs about a pack of beer.
Regulation is more than adequate. I begrudge wasting 30W as heat, but it
saves a transformer.
Steve
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