Let us talk triodesever wondered why many prefer to use triodes instead of pentodes in a single ended amp?
partly because triodes are more linear than pentodes, and the reason for that is,
local negative feedback is already built in with triodes....
with triodes there are two ways to control plate current...
one is by grid voltage and the other is by plate voltage..
mu tends to decrease with increase in plate voltage,
while plate resistance increases with increase in plate voltage...
with triodes, mu and plate resistance are affected by plate voltage,
while transconductance is affected in direct proportion to cathode current...
so where is all this leading to?
a few years ago, i purchased 20 pcs of 21HB5 compactron tv tubes...
as you can see from above heirarchy of tubes, this tube promises to
be even better than the 6AV5 wich have proven to sound good triode wired...
so i picked up my pen and paper and did some rough calculations...
what if i use 10 of these, five bottles per channel?
this tube is rated for 18 watts in a horizontal scanning duty,
but this tube can do more, so that running then at 18 watts is no
big deal, 5 of them paralleled can run 90 watts, so that 20 watts of power is possible,
perhaps more...and considering that these are U$1 tubes...
an added bonus is that just over 300 volts of B+ is required,
no scary voltages need be used...
