[ARC5] Why "Noodling" About Sweep Tubes

[Ian Wilson]

Triode-strapped 6L6 as the master oscillator, perhaps?

73, ian K3IMW


On Tue, Oct 22, 2013 at 9:30 AM, Kenneth G. Gordon
<kgordon2006 at frontier.com> wrote:
> For one thing, of course, the 211 has a plate dissipation rating of at least 50
> watts in the old versions and 100 watts in the "new" versions, like the VT-4C.
>
> Also, it is "single-ended", which makes adapting to a tube with a top-cap
> somewhat of a problem..
>
> I don't know how much "adaptation" you want to indulge in, but I don't know
> of any sweep-tubes with plate dissipation ratings much above about 30
> watts.
>
> In the 191/375, since output is usually no more than 50 watts, I suppose a
> sweep tube with a PD of even 20 watts would be sufficient.
>
> But why a sweep-tube? Those are getting pretty expensive. Even those with
> "weird" filament voltages, like the 21JS6 for instance.
>
> One of the 211s is the master oscillator. I don't know how much power output
> is needed from that tube to drive the final amp (another 211), but I would
> think that any decent NON-BEAM tube could be used. I say NON-BEAM
> tube, since beam-tubes make very poor oscillators, although they have been
> used as such for many years. I cannot, at the moment, think of a non-beam
> tube with "high" output capability, but will dig around a bit.
>
> Perhaps an 811, or even a 572B could be used, although either of those
> would be "overkill" and both are over-priced now...when you can find them.
> "New" ones are being made by the Chinese, though.
>
> As for the final amp, another 211 as I said, since we are talking about 50
> watts output, or something like 75 to 90 watts input, a 6146 or others of that
> family should work just fine.
>
> I think the same thing would go for the modulators, the other pair of 211s
> originally. The 6146 family should work well, even triode-connected.
>
> I suppose we could also substitute other tubes for the final amp 211, some
> which would "look" more like a 211, but all that I know of have a plate cap,
> and some have a side grid cap.
>
> Filament current would have to be taken into account.
>
> Replacing the mic amp, a 10 (or is it a 25) should be relatively trivial.
>
> Well, those are my preliminary thoughts on the matter. YMMV.
>
> Ken W7EKB
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