What's the best tube type to use for a voltage controlled current sink,
with respect to linearity?

I am building plasma tweeters, with a DC glow discharge modulated by audio
(similar to US patent 4,219,705, but I'm using microhollow discharges
(MHCD) as cathodes for the larger discharge to remove cathode fall
instabilities; this technique was unknown during the time of that patent).
My power supply is 2700 V at 400 mA (200 mA for each of two channels for a
stereo setup), ripple filtered to 0.01 V. I'm hoping to have the discharge
drop most of the voltage, and the driving device a lesser portion. The
driver needs to be a voltage controlled current sink at the plasma cathode
(the plasma anode is the high voltage). Since the audio modulation is only
a few percent of the bias, less than 20 mA, essentially I'm concerned with
linearity in a small range around the average operating point. I need to
know what's the best tube type to use in terms of the sound quality, and in
what configuration (grounded cathode or grid, etc.). Most current drives
use pentodes, but I've been told a triode is more linear.

Prune wrote:

What's the best tube type to use for a voltage controlled current sink,
with respect to linearity?

I am building plasma tweeters, with a DC glow discharge modulated by audio
(similar to US patent 4,219,705, but I'm using microhollow discharges
(MHCD) as cathodes for the larger discharge to remove cathode fall
instabilities; this technique was unknown during the time of that patent).
My power supply is 2700 V at 400 mA (200 mA for each of two channels for a
stereo setup), ripple filtered to 0.01 V. I'm hoping to have the discharge
drop most of the voltage, and the driving device a lesser portion. The
driver needs to be a voltage controlled current sink at the plasma cathode
(the plasma anode is the high voltage). Since the audio modulation is only
a few percent of the bias, less than 20 mA, essentially I'm concerned with
linearity in a small range around the average operating point. I need to
know what's the best tube type to use in terms of the sound quality, and in
what configuration (grounded cathode or grid, etc.). Most current drives
use pentodes, but I've been told a triode is more linear.

I don't know the best tube for your application, but I _can_ tell you
that a triode has a quite significantly lower plate resistance than a
pentode; if you really need the current to be independent of plate
voltage then a triode without heavy cathode degeneration isn't the way
to go.

I believe that triodes are more linear when driving a resistive load
exactly because of this lower plate impedance -- if you hold the plate
voltage constant then the plate current vs. grid voltage relationship
isn't any better than a pentode, but if you allow the plate voltage to
vary it provides internal feedback on the tube current.

Hopefully you'll get someone who'll give you a more definitive answer.
Perhaps looking for a newsgroup that involves audio, rather than radio,
homebrewing will help.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

In article ,
says...

What's the best tube type to use for a voltage controlled current sink,
with respect to linearity?

I am building plasma tweeters, with a DC glow discharge modulated by audio
(similar to US patent 4,219,705, but I'm using microhollow discharges
(MHCD) as cathodes for the larger discharge to remove cathode fall
instabilities; this technique was unknown during the time of that patent).
My power supply is 2700 V at 400 mA (200 mA for each of two channels for a
stereo setup), ripple filtered to 0.01 V. I'm hoping to have the discharge

So, 1080 watts of heat dissapation or more just to hear high frequencies???

Is there no other more sensible use of energy for you?? It would seem
that there are several types of tweeter choices that require no energy
other than audio drive that would still perform 10 times better than
your ears ability to determine distortion, and at least 5 times better
than any pickup devices ability to change input sounds into electrical
output.

If you really want to waste energy as heat dissapation, and impress your
audiopill lacky buddies, use a 304TL, or 304TH. 300 watts of plate capacity
with a super high perveance that looks like a plate to heater short if
you drive the grids a little bit positive.

You should turn yourself in to the EnergyStar folks, and do about 100
hours of community service. The crime??? More imagination than true
ability to determine accurate sound reproduction quality.

On Sun, 17 Oct 2004 22:36:54 -0000, (gudmundur)
wrote:

[snip]

|More imagination than true
|ability to determine accurate sound reproduction quality.

Now now. [g] I once had a guy working for me who was supposedly an
engineer and a musician. He claimed, as do a lot of nutty
audiophiles, that he could hear the difference in speaker wire.

These are the folks that will pay $1000/meter for glorified zip cord.

Whoops sorry.... Wire with, "Two conductor Symmetrical Litzwire
construction. There are 285 isolated, multi-gauge, multi-strand, oxide
free/ Lab Grade fiber conductors with FEP® insulation. Eight conductor
symmetrical Litzwire geometry, 95 isolated, multi-gauge, multi-strand,
oxide free / Lab Grade fibers per conductor with FEP® insulation.
Synthetic and natural material wires guides ensure consistent
electricials throughout cable assembly.

Internal Dampening: Guides also act as micro-vibration damper.
Individual wires are configured in an angular displacement to optimize
the self cancellation of noise.

Insulation: Aerospace grade amphorous PTFE® and air insulation. Jacket
material is a polyurethane compound with suspended micro-particles to
reduce static build up."

What I want to know is how this wire knows the difference between
noise and hip-hop.

P.T. Barnum was right.

Wes Stewart wrote:
What I want to know is how this wire knows the difference between
noise and hip-hop.

The electrons' hats have the brims to one side.

--
Most dying mothers say, "I love you, son," or "Take care of your sister."
Why were the last words of Kerry's mother a lecture on integrity?

Behold, Wes Stewart signalled from keyed 4-1000A filament:

snip

Whoops sorry.... Wire with, "Two conductor Symmetrical Litzwire
construction. There are 285 isolated, multi-gauge, multi-strand, oxide
free/ Lab Grade fiber conductors with FEP® insulation. Eight conductor
symmetrical Litzwire geometry, 95 isolated, multi-gauge, multi-strand,
oxide free / Lab Grade fibers per conductor with FEP® insulation.
Synthetic and natural material wires guides ensure consistent
electricials throughout cable assembly.

Did you say that in one breath? :-o

I dare you to do it again! ;-)

--
Gregg t3h g33k
"Ratings are for transistors....tubes have guidelines"
http://geek.scorpiorising.ca

Hip Hop IS NOISE!!!!!!!! Yes good ole PT was right.

Now now. [g] I once had a guy working for me who was supposedly an
engineer and a musician. He claimed, as do a lot of nutty
audiophiles, that he could hear the difference in speaker wire.

These are the folks that will pay $1000/meter for glorified zip cord.

Whoops sorry.... Wire with, "Two conductor Symmetrical Litzwire
construction. There are 285 isolated, multi-gauge, multi-strand, oxide
free/ Lab Grade fiber conductors with FEP® insulation. Eight conductor
symmetrical Litzwire geometry, 95 isolated, multi-gauge, multi-strand,
oxide free / Lab Grade fibers per conductor with FEP® insulation.
Synthetic and natural material wires guides ensure consistent
electricials throughout cable assembly.

Internal Dampening: Guides also act as micro-vibration damper.
Individual wires are configured in an angular displacement to optimize
the self cancellation of noise.

Insulation: Aerospace grade amphorous PTFE® and air insulation. Jacket
material is a polyurethane compound with suspended micro-particles to
reduce static build up."

What I want to know is how this wire knows the difference between
noise and hip-hop.

P.T. Barnum was right.

Wes Stewart wrote:
Now now. [g] I once had a guy working for me who was supposedly an
engineer and a musician. He claimed, as do a lot of nutty
audiophiles, that he could hear the difference in speaker wire.

I used to work with a guy that said he could hear the difference between
gold plated and tin plated RCA connectors.

These are the folks that will pay $1000/meter for glorified zip cord.

Tell them to check out http://www.essentialsound.com/ for the ultimate
in power cord technology.

Don K6LTS

wrote:
Wes Stewart wrote:

Now now. [g] I once had a guy working for me who was supposedly an
engineer and a musician. He claimed, as do a lot of nutty
audiophiles, that he could hear the difference in speaker wire.


I used to work with a guy that said he could hear the difference between
gold plated and tin plated RCA connectors.


These are the folks that will pay $1000/meter for glorified zip cord.


Tell them to check out http://www.essentialsound.com/ for the ultimate
in power cord technology.

Don K6LTS

Oh, honestly. Those parts aren't even dipped in LN2 ferchrissakes!

http://www.jenalabs.com/.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

a écrit dans le message de
...
Wes Stewart wrote:
Now now. [g] I once had a guy working for me who was supposedly an
engineer and a musician. He claimed, as do a lot of nutty
audiophiles, that he could hear the difference in speaker wire.

I used to work with a guy that said he could hear the difference between
gold plated and tin plated RCA connectors.


I seriously doubt that : I've never seen tin plated RCA connectors.

However hearing the difference between gold plated and nickel plated RCA
connectors should be pretty easy for a well trained ear :
Just drop both connectors on a hard surface. Nickel plated and gold plated
shouldn't sound exactly the same.


--
Thanks,
Fred.