3 Sep
2008
3 Sep
'08
12:55 a.m.
William Blair wrote:
Brent Hilpert wrote:
Great, you're already there, didn't realise from your earlier posts that you
were looking at such off-the-beaten-path tubes. I forgot there were so many
duo-triodes in that class with 4,5,8V,etc. filaments (don't tell the audio tweaks).
Make something using enough tubes and one can wire up the filaments in series
as they
were intended for..
It has occurred to me that if one were setting
out to build
a (small?) tube
computer today for fun, to look into selecting the primary
tube(s) from that
class; the question being if one would do any better than
just using
duo-triodes, which are in higher demand.
That's exactly what I'm doing. The advantage of going with tube
currently used for audio is that they are still in production,
mostly in China and Russia. The disadvantage is that they cost
quite a bit more. For small projects like mine, I have no worries
about the availability of tubes that are no longer produced. For
that matter, I suspect that even very large projects wouldn't
have problems with tube availability considering how many of these
out of production tubes are apparently still around. For instance,
I can buy OOP 5BK7A dual triodes for US$0.78 each (I have ten on
hand) or OOP 4BS8 dual triodes (to be purchased on my next order)
for $0.38 each. The 5BK7A has a 4.7V heater and the 4BS8 a 4.5V
heater. Either of these would work fine at 5V being outside of
the typical filament voltage +/-10% rating only very slightly in
the case of the 4BS8.
..