"patrick-turner" wrote in message
...
Me again folks. I wrote a new page about using a differential input pair
of triodes for a PP amp. See my page at
http://www.turneraudio.com.au/basic-tube-5.html
Brick bats, buckets of poop, poisoned arrows, drone delivered ordinance
all tolerated, but returned to sender with gusto.
Patrick Turner.
Alex:
I skimmed this page.
Noticed an error in the MJE340 current source circuit in the first
schematic. (Correct in the others.)
Noticed a typo "oft3en" in the first line of the section "DRIVER STAGE
DIFFERENTIAL AMP".
Was pleased that the term "differential stage" is widely used, and that
arcane "long tail pair" is only occasionally -- sort of being phased out.
Did not understand the purpose of long and distracting
calculations/speculations about mu and gain... Was it all to point out that
the actual mu of 6CG7 is 22, not 20 as quoted in the datasheets?
There were no explanation why the tubes with mu around 20 are preferred.
Obviously, 12AX7 is not a good candidate because it can not work with a
decent current, but 12AT7, 6BQ7, ECC85 seem even better than 6CG7 because of
higher mu, larger Gm and about the same current.
Again, I did not read the whole article attentively. Perhaps there are some
other minor errors...