Robert Casey wrote:

Sander deWaal wrote:




Don't forget the rimlock type ECC40.
With specs similar to the 6SN7, it's a very sweet sounding tube and
useful in many applications.
I think this tube is one of the most underestimated tubes for audio
use.
This has advantages, too. You can buy buckets full of them for next to
nothing.


There's a pdf file at:
http://www.mif.pg.gda.pl/homepages/f...46/e/ECC40.pdf
with many app notes for this tube. And it is mentioned that the cathode-
heater voltage rating is 175V, higher than most similar tubes. That would
make those SRPP circuits more possible.

As for sockets, you could just disassemble an ordinary socket and use
the metal parts to grab the tube pins. Arrange them in a suitable pattern
on a circuit board. Or use the pins from a female D computer connector,
those look about the right size at least for regular 7 and 9 pin miniature
tubes.

The ECC40 is a nice tube for DIY folks with plenty of time to
addapt something for the oddball 8 pin arrangement.
If it ain't octal, or 9pin miniauture, or possibly 7 pin miniature,
then its not a good choice for any commercial design, ppl would have trouble
sourcing the tube.

Its specs are very similar to ECC32, which are octal based twin triodes,
Ra = 14k, U = 30 ( approx ).

Both ECC32 and 40 have rather too much gain for a line stage,
and it has to be reduced and current FB is one way, but to me a 12AU7
with its already low gain is a bit easier.

Its no wonder the ECC40 is plentiful and cheap, the makers
made a mistake to use a pinout so different to the status quo
of octal, 9&7 minis.

Then there was noval, for 7868, etc.Why would anyone use 7868 now?
Maybe if they made a new version with an octal socket, yes,
but why oh why was the noval socket ever made?!
Loctal was also brought in for milspec gear to prevent tubes falling out of
sockets.
OK, the damn military must have bomb proof gear.
There is no place now for loctals in civi street.
And then came transistors, so a huge diversity of tube socketting was never
developed,
which was really good for us now!
Imagine if we had had 100,000 different types of twin triodes,
with 50 different sockets, and a very limited production of any of them.

Luckily, only about 30 different tubes need to be produced for audio amps
in the world now.
That makes it easy for the russian factories.
In 1960, maybe 4,000 types were being made.

Patrick Turner.