Eeriely quiet here at RAT. Here's an idea for one
type of 'ideal driver' tube:

Should be possible to stack without much effort,
so large Vk-Vff must be allowed with an
indirectly-heated cathode.
Large emission, triode grid with high current
capability, possibly with foil instead of wire ?

In this way, direct headphone output's could be
realized with an inverted topology, see eg. on
Steve Bench's page
http://members.aol.com/sbench102/inverted.html

and of course other usefull configurations.
Ideas out there ?
Rudy

EC8010 and EC8020,
some other pentodes wired in triode;
10Y also-but on another end of the tale.

--
--
.................................................. ........................
Choky
Prodanovic Aleksandar
YU

"don't use force, "don't use force,
use a larger hammer" use a larger tube
- Choky and IST"
- ZM
.................................................. ...........................
"Ruud Broens" wrote in message
...
Eeriely quiet here at RAT. Here's an idea for one
type of 'ideal driver' tube:

Should be possible to stack without much effort,
so large Vk-Vff must be allowed with an
indirectly-heated cathode.
Large emission, triode grid with high current
capability, possibly with foil instead of wire ?

In this way, direct headphone output's could be
realized with an inverted topology, see eg. on
Steve Bench's page
http://members.aol.com/sbench102/inverted.html

and of course other usefull configurations.
Ideas out there ?
Rudy

Ruud Broens wrote:

Eeriely quiet here at RAT. Here's an idea for one
type of 'ideal driver' tube:

Should be possible to stack without much effort,
so large Vk-Vff must be allowed with an
indirectly-heated cathode.

Yes. This technology exists, and was put to use in the line-operated
television sets. It's actually amazing how much Vk-Vff some of the
ordinary television tubes can safely withstand.

Large emission, triode grid with high current
capability, possibly with foil instead of wire ?

I think I see what you're getting at. The foil surface would be
perpendicular to the cathode surface, right? (If parallel, it wouldn't
work very well, because for a grid to operate properly the area of the
grid material must be small compared to the open area.)

I can see this being difficult to construct. On the other hand, it would
be rather like a "slinky" toy, and they don't seem to have trouble
making slinkies. ;-)

But it might be easier to use a frame grid construction method, and use
a stack of "washer"-shaped discs instead of a continuous spiral.

In this way, direct headphone output's could be
realized with an inverted topology, see eg. on
Steve Bench's page
http://members.aol.com/sbench102/inverted.html

Ah! Good thought. The output resistance could indeed be made quite low
that way. The only real drawback is the terribly low transconductance in
inverted mode, requiring prohibitively high drive voltages on the
control element (plate).

This could probably be greatly improved by placing the plate as close to
the grid as possible. Interestingly, I've marvelled at how close the
plate is to the grid/cathode in the large triode section of the 6EM7 and
other dual dissimilar triodes. I would imagine these would make pretty
good inverted-mode drivers, except for the conventional wire grids.

and of course other usefull configurations.
Ideas out there ?

How about stacked triodes, with bipolar supplies (so that the output is
ground-referenced), drive to the upper triode, with the lower triode
simply there as a counterpoise. Consider it sort of an "active voltage
follower" (or the opposite of a mu follower, in which the lower tube is
driven).

Another point - since we're talking transformerless designs,
conventional NFB techniques would work very well to reduce the effective
output impedance. Should be practical to drive 32-ohm headphones even
with a 6SN7.

Cheers,
Fred
--
+--------------------------------------------+
| Music: http://www3.telus.net/dogstarmusic/ |
| Projects: http://dogstar.dantimax.dk |
+--------------------------------------------+

Ruud Broens wrote:

Eeriely quiet here at RAT. Here's an idea for one
type of 'ideal driver' tube:

Should be possible to stack without much effort,
so large Vk-Vff must be allowed with an
indirectly-heated cathode.


Yes. This technology exists, and was put to use in the line-operated
television sets. It's actually amazing how much Vk-Vff some of the
ordinary television tubes can safely withstand.

Large emission, triode grid with high current
capability, possibly with foil instead of wire ?


I think I see what you're getting at. The foil surface would be
perpendicular to the cathode surface, right? (If parallel, it wouldn't
work very well, because for a grid to operate properly the area of the
grid material must be small compared to the open area.)

I can see this being difficult to construct. On the other hand, it would
be rather like a "slinky" toy, and they don't seem to have trouble
making slinkies. ;-)

But it might be easier to use a frame grid construction method, and use
a stack of "washer"-shaped discs instead of a continuous spiral.

In this way, direct headphone output's could be
realized with an inverted topology, see eg. on
Steve Bench's page
http://members.aol.com/sbench102/inverted.html


Ah! Good thought. The output resistance could indeed be made quite low
that way. The only real drawback is the terribly low transconductance in
inverted mode, requiring prohibitively high drive voltages on the
control element (plate).

This could probably be greatly improved by placing the plate as close to
the grid as possible. Interestingly, I've marvelled at how close the
plate is to the grid/cathode in the large triode section of the 6EM7 and
other dual dissimilar triodes. I would imagine these would make pretty
good inverted-mode drivers, except for the conventional wire grids.

and of course other usefull configurations.
Ideas out there ?


How about stacked triodes, with bipolar supplies (so that the output is
ground-referenced), drive to the upper triode, with the lower triode
simply there as a counterpoise. Consider it sort of an "active voltage
follower" (or the opposite of a mu follower, in which the lower tube is
driven).

Another point - since we're talking transformerless designs,
conventional NFB techniques would work very well to reduce the effective
output impedance. Should be practical to drive 32-ohm headphones even
with a 6SN7.

Cheers,
Fred
--
+--------------------------------------------+
| Music: http://www3.telus.net/dogstarmusic/ |
| Projects: http://dogstar.dantimax.dk |
+--------------------------------------------+

"Fred Nachbaur" wrote in message
news:RoVrb.16606$jy.13266@clgrps13...
:
:
: Ruud Broens wrote:
:
: Eeriely quiet here at RAT. Here's an idea for one
: type of 'ideal driver' tube:
:
: Should be possible to stack without much effort,
: so large Vk-Vff must be allowed with an
: indirectly-heated cathode.
:
: Yes. This technology exists, and was put to use in the line-operated
: television sets. It's actually amazing how much Vk-Vff some of the
: ordinary television tubes can safely withstand.
:
: Large emission, triode grid with high current
: capability, possibly with foil instead of wire ?
:
: I think I see what you're getting at. The foil surface would be
: perpendicular to the cathode surface, right? (If parallel, it wouldn't
: work very well, because for a grid to operate properly the area of the
: grid material must be small compared to the open area.)

Jaja, of course Actually, could be a little less adventurous there,
using a rectangular profile wire grid, say n*2n would help. So would
coating the posts with diamond, which amazingly has 5 times the
thermal conductivity of copper! Using a grid heat fin like in the
6AS7G's would be the icing on the cake.
Rudy
:
: I can see this being difficult to construct. On the other hand, it would
: be rather like a "slinky" toy, and they don't seem to have trouble
: making slinkies. ;-)
:
: But it might be easier to use a frame grid construction method, and use
: a stack of "washer"-shaped discs instead of a continuous spiral.
:
: In this way, direct headphone output's could be
: realized with an inverted topology, see eg. on
: Steve Bench's page
: http://members.aol.com/sbench102/inverted.html
:
: Ah! Good thought. The output resistance could indeed be made quite low
: that way. The only real drawback is the terribly low transconductance in
: inverted mode, requiring prohibitively high drive voltages on the
: control element (plate).
:
: This could probably be greatly improved by placing the plate as close to
: the grid as possible. Interestingly, I've marvelled at how close the
: plate is to the grid/cathode in the large triode section of the 6EM7 and
: other dual dissimilar triodes. I would imagine these would make pretty
: good inverted-mode drivers, except for the conventional wire grids.
:
: and of course other usefull configurations.
: Ideas out there ?
:
: How about stacked triodes, with bipolar supplies (so that the output is
: ground-referenced), drive to the upper triode, with the lower triode
: simply there as a counterpoise. Consider it sort of an "active voltage
: follower" (or the opposite of a mu follower, in which the lower tube is
: driven).
:
: Another point - since we're talking transformerless designs,
: conventional NFB techniques would work very well to reduce the effective
: output impedance. Should be practical to drive 32-ohm headphones even
: with a 6SN7.
:
: Cheers,
: Fred
: --
: +--------------------------------------------+
: | Music: http://www3.telus.net/dogstarmusic/ |
: | Projects: http://dogstar.dantimax.dk |
: +--------------------------------------------+
:

"Ruud Broens" wrote in message
...
Should be possible to stack without much effort,
so large Vk-Vff must be allowed with an
indirectly-heated cathode.

Stacking = SRPP, et al?

Large emission, triode grid with high current
capability, possibly with foil instead of wire ?

Foil where?

Drivers don't need much current capability unless you're trying to
drive something unusually capacitive (say, 20 12AX7s in parallel)
and/or requiring grid current (which the above would for any useful
power output, but I'm really getting more at 811, 572-10 and -3 and
other class 2 power triodes).
Typically, you don't bother with a 6AS7G to drive a 6BQ5. You match the
driver to the output tube; any more is useless. Of course, this point is
moot if you are Weird "Happy Ears" Al..
Even if you don't, you can still get away with something otherwise-
hopelessly underpowered, like a 12AX7, by using it as a CF in front of
the output tube.

In this way, direct headphone output's could be
realized with an inverted topology, see eg. on
Steve Bench's page
http://members.aol.com/sbench102/inverted.html

Why is this necessary? Are we talking driving tubes, OPTs, what?

For headphones in general, a CF is more than adequate, and a 6AS7 will
give you more than enough power with any headphones to blow your ear
drums straight into your corpus callosum.
Especially with high-Z headphones (100 ohms let's say), a 12AU7 or
similar will give more than adequate results. You can even go white CF
or SRPP if you want.

Tim

--
"That's for the courts to decide." - Homer Simpson
Website @ http://webpages.charter.net/dawill/tmoranwms

Tim Williams wrote:

"Ruud Broens" wrote in message
...

[...]

Large emission, triode grid with high current
capability, possibly with foil instead of wire ?


Foil where?

Drivers don't need much current capability unless you're trying to
drive something unusually capacitive (say, 20 12AX7s in parallel)
and/or requiring grid current (which the above would for any useful
power output, but I'm really getting more at 811, 572-10 and -3 and
other class 2 power triodes).

I think he's using the term "driver" in the sense of "headphone driver"
not necessarily as a "driver stage" (before a final stage). He's also
examining a specific topology -- inverted mode - i.e. input on plate,
output on grid. The grid structure would therefore have to be capable of
drawing significant currents, and hence the idea of planar foil sheets
or a planar helix to allow more heat dissipation than wires.

Typically, you don't bother with a 6AS7G to drive a 6BQ5. You match the
driver to the output tube; any more is useless. Of course, this point is
moot if you are Weird "Happy Ears" Al..

Yeah, seems to me some goof even drives a raft of 12AU7's with a 6SN7.

Even if you don't, you can still get away with something otherwise-
hopelessly underpowered, like a 12AX7, by using it as a CF in front of
the output tube.


In this way, direct headphone output's could be
realized with an inverted topology, see eg. on
Steve Bench's page
http://members.aol.com/sbench102/inverted.html


Why is this necessary? Are we talking driving tubes, OPTs, what?

It's not "necessary," it's a speculation. He's specifically thinking of
the output tube(s) that "drive" a headphone, hence a "headphone driver".
(I think anyway? Right Rudy?)

For headphones in general, a CF is more than adequate, and a 6AS7 will
give you more than enough power with any headphones to blow your ear
drums straight into your corpus callosum.
Especially with high-Z headphones (100 ohms let's say), a 12AU7 or
similar will give more than adequate results. You can even go white CF
or SRPP if you want.

Both of which are detailed he
http://www.tubecad.com/may2000/page16.html

Cheers,
Fred
--
+--------------------------------------------+
| Music: http://www3.telus.net/dogstarmusic/ |
| Projects: http://dogstar.dantimax.dk |
+--------------------------------------------+

"Tim Williams" wrote:
in ,

: drums straight into your corpus callosum.

And here's the perfect track to play with it;-)
"Crossing The Corpus Callosum"
http://www.iclassics.com/iclassics/a...lectionId=3826

The second is quiet; the third, beautifully laid back ... who might agree?
I have a vinyl copy, still in good condition. There are some other nice
albums (and artists) listed in each of the players discographies. (IMHO
http://www.ecmrecords.com/ecm/recordings/1351.html

I developed a fondness for quite a lot of music from ECM, late 80's on.

Ross

"Fred Nachbaur" wrote in message
news:e9_rb.21383$jy.5501@clgrps13...
The grid structure would therefore have to be capable of
drawing significant currents, and hence the idea of planar foil sheets
or a planar helix to allow more heat dissipation than wires.

Indeed. For existing tubes, you could search for some with really
gi-normous grid support wires.

Yeah, seems to me some goof even drives a raft of 12AU7's with a 6SN7.

But there's a crappy IST in there so all is forgiven, right? ;-)

And, lest we forget that design for quad 6146s that someone drew up,
using a pair of 6CL6s (capable of 10-15W with good weather) resistance-
coupled, delivering 1W into tubes that need all of .1W driving power.

It's not "necessary," it's a speculation. He's specifically thinking of
the output tube(s) that "drive" a headphone, hence a "headphone driver".
(I think anyway? Right Rudy?)
^^^
My point exactly. I think he might've had a few before he posted, but
alas, all the better to enjoy the music with, eh? ;-)

Rudy, could you please be more specific?

Tim

--
"That's for the courts to decide." - Homer Simpson
Website @ http://webpages.charter.net/dawill/tmoranwms

"Tim Williams" wrote in message
...
: "Fred Nachbaur" wrote in message
: news:e9_rb.21383$jy.5501@clgrps13...
: The grid structure would therefore have to be capable of
: drawing significant currents, and hence the idea of planar foil sheets
: or a planar helix to allow more heat dissipation than wires.
:
: Indeed. For existing tubes, you could search for some with really
: gi-normous grid support wires.
:
: Yeah, seems to me some goof even drives a raft of 12AU7's with a 6SN7.

:
: But there's a crappy IST in there so all is forgiven, right? ;-)
:
: And, lest we forget that design for quad 6146s that someone drew up,
: using a pair of 6CL6s (capable of 10-15W with good weather) resistance-
: coupled, delivering 1W into tubes that need all of .1W driving power.
:
: It's not "necessary," it's a speculation. He's specifically thinking of
: the output tube(s) that "drive" a headphone, hence a "headphone driver".
: (I think anyway? Right Rudy?)
: ^^^
: My point exactly. I think he might've had a few before he posted, but
: alas, all the better to enjoy the music with, eh? ;-)
:
: Rudy, could you please be more specific?
:

You mean, 'bout those drinks, or..
Well, i did start off with 'one type of ideal...', so yes, here i was
specifically
thinking of headphone-driving solutions not by topology, but by a tube
designed for that purpose.
Rudy
: Tim
:
: --
: "That's for the courts to decide." - Homer Simpson
: Website @ http://webpages.charter.net/dawill/tmoranwms
:
: