[Crowbar]

Quote:

Originally Posted by Psiga /img/forum/go_quote.gif Notice how it rolls off at 15kHz, and is really jagged below 50Hz?

Are you ******** me? The magnitude of those variations is tiny compared to variations of any normal headphones. Look at the scale on the vertical axis and compare to typical headphones:

Quote:

So the question is, can we find a small modern transistor more effective for our purposes than the BUX87.

That amp is bad design, stacking transistors like that. Forget it and use tubes. You don't need the HV stuff in the headphone driver; put it in an amp box, just like electrostatic headphones do.

 

[Carl]

Quote:

Originally Posted by Psiga /img/forum/go_quote.gif Haw haw. ;p Tubes existed back in the '80s, of course, but the suckerpunch here is that we want something small enough to fit on the headphones themselves. This image shows what we're dealing with. Admittedly, having two functioning 300B tubes sticking off the head would go down in audiophile history... But yeah, we'll stick with solid state for now. I'm just curious to know if there are any solid state transistors which could do the whole 3kV step without affecting the audible frequency response.

Why does it need to be enclosed in the earcups? Koss did their e-stats that way back in the day, but eventually learned the folly in doing so.

Yes, I respect we're talking about more than a simple HVDC bias supply here, but I don't see why you couldn't make it external. High voltage+high heat+small size would also push you towards unpleasent capacitor choices and the earcups would likely end up heavier than would be ideal.

There are 3kV transistors available now (and even 6kV, I think), but I'm not aware of any with any audio pedigree.

 

[Crowbar]

Comparative responses with matched scales.

 

[Carl]

Quote:

Originally Posted by Crowbar /img/forum/go_quote.gif Comparative responses with matched scales.

Metalized mylar cones vs. plasma discharge. Now that's a fair fight!

 

[Crowbar]

Electrostatic headphones are just as bad:

 

[Carl]

Quote:

Originally Posted by Crowbar /img/forum/go_quote.gif Electrostatic headphones are just as bad:

Well that graph is rather off. I've listened to the O2s extensively and they are respectably linear, even though certainly not perfect. They certainly don't drop 20dB between 700Hz and 2.2kHz.

 

[Psiga]

If it is feasible to do outboard voltage stepping, then that'll be great. I went on presuming that the voltage transistors were built into the earpieces for a reason, and that it'd be easier to replicate the design on the cheap if we didn't stray too far from the original design. If Crowbar figures that external will work as well or better, then that gives more options.

As for the frequency plots: Yeah, the whole five decibel linear roll-off between 15 and 20 kHz is of course staggeringly impressive. I just remember that plasma arc tweeters can go pretty flat up to 50kHz~100kHz depending on source. I'm hoping that the onboard transistors were just an odd French idea.

Errr... Okay, after pondering this for a while, it occurs to me that they don't seem to be modulating the HV emitter, so much as moving the ionized air that the filaments are producing. Is that a more accurate assessment? If that's the case, then they are not actually like plasma tweeters, and we're probably going to be contending with a backwave.

 

[Psiga]

Hm. Crowbar, what do you know about the ozone neutralizing screens? I've spent a bit over an hour roaming the hintergoogles in search of information. The only membrane material that I've found is Nafion, a form of doped Teflon, and even that doesn't look reassuringly promising.

 

[Crowbar]

Standard platinum-iridium-palladium used in catalytic converters would decompose both ozone and nitrogen oxides. Note I'm talking about hot plasma though, as in the Plasmatronics stuff; not the corona discharge headphones. One needs the right temperature for the catalyst to work; and certain temperature ranges would cause decomposition of these just by the heat of the plasma.

 

[Psiga]

Mh. Roger that.

Disappointing to hear, in a way, but intriguing at the same time. Of course there's no available data on how much ozone the Plasmasonic 1 puts out, so I guess the only way to discover will be to make a replica and obtain an ozone meter reading. With irritating odor at .01 ppm, and serious hazard at .1 ppm, I wonder what having two unintentional ozone generators 6" from the mouth and nose would be like.

Do you think the grids surrounding the emitter are nearly as much a source of ozone production as the emitter itself? Or are they just pulling/modulating the already existing ions, without producing more? (Heh, I am such a plasma n00b. Thank you for your insights.)

 

[Carl]

Quote:

Originally Posted by Psiga /img/forum/go_quote.gif Do you think the grids surrounding the emitter are nearly as much a source of ozone production as the emitter itself? Or are they just pulling/modulating the already existing ions, without producing more? (Heh, I am such a plasma n00b. Thank you for your insights.)

My guess is that the reactions would occur at the virtual cathode and/or virtual anode, rather on the physical electrodes themselves, although ionization has never been my forte either.

 

[Crowbar]

Reactions occur near the electron emitters.

 

[Akathisia]

This thread is awesome. Keep it up, I'm on the edge of my seat!

 

[Crowbar]

Bored much?

 

[synaesthetic]

lotta thread necromancy going on here recently...