Re: Persistence seems lacking...

James Daldry W4JED

Hi, Braden

The secret of "nice warm sound" is to have a small amount of distortion at all audio levels. Audio output beam tubes work better as switches than as linear amps, so they require substantial amounts of negative feedback to linearize them. But substantial negative feedback means throwing away audio gain, possibly even adding another amplifier stage (at considerable expense) to cover for the lost gain. The usual result is to use only a little feedback to get decent bandwidth, then live with 1 or 2 percent THD at all volume levels. Then you end up without the "brick wall" clipping you get with most solid state equipment. Soft, roundy edges.

You can get very similar sound by building an amp using depletion mode FET's.



On 9/9/19 9:19 AM, Braden Glett wrote:
"PS is anything still driven by valves?"

Yes - plumbing. Other than that, you should probably have the hobby of working on guitar amplifiers rather than radio! :) Amps still use tubes for that nice, warm sound, real or imagined.

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