Here's a bunch of nice low power triodes to use in PP amps - two or
three pairs per side. I've used 12b4, 6S4 and 6CK4 and they all sound
extremely nice, but I haven't used them in the same amp. Has anybody
compared any of these directly and can comment on sound quality?
Thanks, Andy

Andy Evans wrote:

Here's a bunch of nice low power triodes to use in PP amps - two or
three pairs per side. I've used 12b4, 6S4 and 6CK4 and they all sound
extremely nice, but I haven't used them in the same amp. Has anybody
compared any of these directly and can comment on sound quality?
Thanks, Andy

6BX7 may be an even better choice, due to plate dissipation rating. And
with one tube in the output you can get a PP Amp if you like. I did an
article on a SET amp using a 6EA7/6EM7 that worked out very well. Used
the high mu triode as the driver in a feedback pair combo.

My 2 cents, anyway

Cheers, John Stewart

The dissimilar triodes are definitely worth a try. I have some 6EW7 and
6DN7. The beefy sections are good sounding, but one is at the mercy of
the smaller triode in terms of sound quality for the input. I wasn't
convinced by the first half of the 6EW7, I must say. I should try again
with a diff pair over a CCS.
I have some 6BX7. Problem here is price - the 12b4, 6S4 and 1626 are $2
tubes. 6AH4 nearer $4 and 6CK4 a bit more still. At some point you meet
Sovtek 2a3 tubes, which then become a better choice, then 845, then
300b. The attraction was all triode ouput stages with $2 tubes.

I loved the 6DN7 when I built the SEX (Single Ended Experimenter's
amp), a kit sold by Electronic Tonalities of Poulsbo, WA. Excellent
sound. I didn't share your opinion that the driver section was not up
to the same standard as the power section. It may be a matter of
implementation. I honestly doubt you'll be picking up 6DN7 for two
bucks a pair ever again... It would make a nice little booster amp in a
single envelope for a DHT.

Andre Jute

Andy Evans wrote:
The dissimilar triodes are definitely worth a try. I have some 6EW7
and
6DN7. The beefy sections are good sounding, but one is at the mercy
of
the smaller triode in terms of sound quality for the input. I wasn't
convinced by the first half of the 6EW7, I must say. I should try
again
with a diff pair over a CCS.
I have some 6BX7. Problem here is price - the 12b4, 6S4 and 1626 are
$2
tubes. 6AH4 nearer $4 and 6CK4 a bit more still. At some point you
meet
Sovtek 2a3 tubes, which then become a better choice, then 845, then
300b. The attraction was all triode ouput stages with $2 tubes.

I loved the 6DN7 Excellent sound. I didn't share your opinion that the
driver section was not up to the same standard as the power section.

I was talking about the 6EW7 in fact - I haven't tried the 6DN7. I have
some so I really should take a listen. Do you know the other tubes
mentioned? Andy

Andy Evans wrote:

I was talking about the 6EW7 in fact - I haven't tried the 6DN7. I
have
some so I really should take a listen. Do you know the other tubes
mentioned? Andy

Sorry, I don't. I just checked my new tubes and I see I have 12BH7A and
12BZ7 sent to me by a Canadian amp maker as beefy little drivers (he
asked to have one of my books and sent me eight superb Johnson UX4
sockets and these tubes in return) but I haven't done anything more
than just plug them in for a quick listen.

The problem is that once you have a stash of 417A, you tend to reach
automatically for them. Mine probably cost three bucks each, a bargain
for a beefy and brilliant tube. And if a 417A is "too expensive", I
like 6SL7 and 6SN7, of both of which I have stashes of selected,
matched tubes bought back in the days (less than ten years ago!) when
you couldn't give them away and I got them basically for postage or as
a return gifts from people I sent worn Mullard pentodes just so they
could say they tried them. (Some are still using tubes I chucked out
back then, claiming they can't buy anything better.)

I do know *of* the 1626 though. Search on the net for Bob Danielak,
Jeremy Epstein and Darling in conjunction with 1626, the last being the
name of a series of 1626 amps all flowing from a Bob Danielak design
with 1626. Bob is the guy who "discovered" the 1626 as an audio tube.

Andre Jute

wrote:
It may be a matter of
implementation. I honestly doubt you'll be picking up 6DN7 for two
bucks a pair ever again..

Don't overlook tubes like 8CG7 and such oddball heater voltage
variants of our favorites. Can usually be had for cheap.
8V heater tubes can be run off of 12VAC with the use of a series
rectifier diode (like a 1n4004) without filtering. As it's
v^2/R = power, 8.4^2=72 and half of 12^2=144/2=72. Half
because the diode blocks half the AC waveform.

I'm talking output valves here. 6SN7s can be used as output valves, but
you need quite a few of them. I've heard an amp using them as outputs
and it was, in fact, quite wonderful though low power. No - I'm looking
at tubes with plate dissipation in the range 5 watts (1626) to 12 watts
(6CK4) . So two pairs of 6CK4 or 6AH4, two or three pairs of 6S4 or
12b4, and three pairs of 1626 to get you to a PP amp with around 7 or 8
watts output. I was thinking single triodes for convenience, but
there's the 6BX7 and 6N30 which would work, for instance. Andy