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

First, thanks for the reply. Second, I apologize for the length of this
reply.

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

Hey, if I'm paying for it, why not. You sound like one of those nutty
environmental activists. You know the types, that would force decreased
energy use down people's throats so that their pet projects like wind and
solar power can provide enough energy, thus completely ignoring the fact
that most of the world population in third world and developing countries
will have its per capita energy use jump orders of magnitude to approach
that of developed countries in the coming decades -- you'd need to cover
the planet with windmills to provide enough. And for what? Even if fusion
doesn't work out (and aparently the ITER project members including the US,
EU, Japan, Russia, Singapore and others think it will, and have already
planned out the first over-unity reactor to begin construction within a few
years; see iter.org), the existing technology of fission breeder reactors
can provide essentially unlimited power even with the current minable
supply of ~7x10^6 tonnes of uranium. Energy shortages are artificial and
politically imposed.

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

Where did that number come from? THD measurements generally do not
correlate with human perception. For example, see
http://www.gedlee.com/distortion_perception.htm and the numbers in the
table there. Better yet, check out their papers in the Audio Engineering
Society; you can find other similar developments by searching the Web. The
specific types of distortion are far more important than some summary
statistic like THD or IMD. The analogy is a population with an unusual
distribution, and using an arithmetic mean to describe it -- say some third
world village, and 50 people in it make $1/day, and 1 makes $100.
Obvioiusly the mean, being almost $3, is a pretty poor descriptor of rich
the villagers are. The point is that this far there is a lack of a good
metric correlating fully with human perception of audio quality. This is
why, for example, when some institution or company is developing a new
audio (likewise for video) compression codec, blind testing with human
subjects is always performed during evaluation. I'm not to say that there
isn't tons of snake oil and over-the-top nonsense and scams caused by
marketing departments in high-end audio business (that's why I've built
every component of my system except the DVD player). But the people that
go to the other extreme and say that everything sounds the same are also
wrong. Initially people thought jitter in early CD players was a non-
issue, because being measured in picoseconds, it was thought to be
imperceptible. This turned out completely wrong, and the technology had to
be corrected. Look now at TI and Cirrus and Analog Devices datasheets for
DACs and ASRCs, and they mention jitter quite a lot. Indeed, it turned out
that poor disc mastering can introduce jitter that sounded so bad that
recently under complaints from artists Sony changed some manufacturing
steps to eliminate the problem. Another example of people not measuring
the right things is that discontinuities in the phase distortion screw up
perception of direction. And even ultra-conservative audio engineers like
D. Self has admitted that electrolytic capacitors cause distortion, and
that thermal distortion exists at least in integrated circuit amplifiers
(and this is an example of a type of distortion that does not affect THD
and IMD numbers). And so on. Finally, it is of note that a single blind
test that shows no result is no proof that a difference is inaudible. For
statistical significance, a number of trials is needed and there are very
very few examples of such studies in audio perception.

than any pickup devices ability to change input sounds into electrical
output.

Yes. But why add more distortion than there already is? Also, formats
like SACD and DVD-Audio are often digitized directly from the original
master tapes (in the case of non-new recordings), thus doing away with some
of the damage that has been done. These formats also use 24-bit encoding to
deal with the problem that 16-bit audio does not achieve the full dynamic
range that the ear is capable of perceiving (technically 16 bits are
enough, but in practice actual 16-bit equipment is not able to achieve the
theoretical maximum).

If you really want to waste energy as heat dissapation, and impress
your audiopill lacky buddies

LOL, I have no audiophile buddies, other than some people I argue with on
online forums. The funny thing is that usually I'm arguing the other side,
the skeptic. The truth is, I may very well not be able to tell a
difference between this and a quality dynamic or electrostatic tweeter. On
the other hand, I'm sure decent tweeters existed during the 1980s when
Hill's Plasmatronic speakers were made, and Hill is a PhD working for the
military on plasma and laser reasearch, so I think he's got his feet firmly
planted in the real world. Also, how do I know that even if some change I
make to my system that by itself makes a difference so small I can't hear
it, multiple changes' cumulative effect won't be detectable? And finally,
even if it makes no difference, it's the coolness factor of outrageous
upgrades (someone called it audiophile equipment fetishism). Even though I
know for sure I couldn't hear the difference between cables, I still made
interconnects out of fine silver and teflon. I know full well any
conductor will sound the same, and that dielectric absorption is not an
issue at audio frequencies, so the teflon is pointless. But that's not the
point. And even with cables, it turns out resistance is not all that
matters. For example, consider the case of a passive preamplifier (or a
potentiometer volume control at the output stage of the source) feeding a
power amp with a not very high input impedance. A number of commercial
interconnects have sufficient capacitance to affect the audible frequency
response in this situation.

use a 304TL, or 304TH. 300 watts of plate capacity

I don't need that much dissipation ability. What about a 152TL so I can
save some money? Would that have sufficent perveance? In the end, all I
care about is linearity within a range of ten or so mA around the operating
point of about 180 mA. Would these types of triodes be better than
pentodes? And finally, I've seen these TL and TH suffixes often, but I
never figured out what's the difference (the datasheets look about the
same).

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.

You should join David Suzuki's cronies or Green Peace Terrorists Inc. or
something

In article ,
says...

Sorry for the top post, but here is the TL/TH deal

TL triode low gain, generally about 10
TH triode high gain, generally 40 to 100
Why the 304TL or 304TH, and not the others?? The 304TH is 4 75TH
triodes in parallel in one bottle, and the perveance is so far above
and beyond anything except perhaps a television horizontal output
sweep tube tetrode, or pentode. The sweep tubes probably won't have
enough dissapation unless you parallel them up.



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.

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