Re: VTTC Multi-tube oscillator?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

At 05:30 PM 9/26/2002 -0600, you wrote:
>Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" 
><Mddeming-at-aol-dot-com>
>
>Hi All toobers (tubers - Tesla potatoes???);-))
>
>1)      I recently acquired five (5) "slightly-used" 833As and a Chinese FU-33
>look-alike, with a possibility of three more coming, and four 575As for
>rectification of plate supply.  I am looking at the possibilities of a large
>VTTC. This will be my first VTTC since the tiny 6L6 -based coil I built in the
>1960s. One possibility is to strap a bunch of the 833s in parallel, but if I
>remember correctly, load-balancing in many parallel tubes is worse than tuning
>up a 1950s V12 Jaguar. Another possibility is to make a small oscillator and a
>monster amplifier, but I'm not sure if this isn't just complicating the
>circuitry and leaving the same problems.
>2) Not having a "steroid-powered" tube tester, is there any way to check the
>tubes before building the VTTC and trying them? If not, has anyone got a
>serious tester schematic?
>3) Sell all the tubes to someone on the list and buy one much bigger tube?
>Thanks,
>Matt D.


Historically, the cost/benefit in commercial applications has always pushed 
towards one big tube over the array of smaller tubes.  The big driver for 
this is just as you say, they've got to work together.

However, for surplus, the equation might change... you might be able to get 
10 tubes with an output power of 1 each for a LOT less than a single 10x 
tube.  Add that to the fact that you probably don't need the ultimate best 
performance so the matching issue might not be insurmountable (i.e. you're 
willing to settle for 9x performance from 10 tubes...)

One practical advantage to running a lot of tubes, if they have filaments 
isolated from the cathode, is that you can run the filaments in series... 
much easier to come up with a 100V supply at 10 amps than a 10 volt supply 
at 100 amps...