ChiUnuion-Fi

[spritzer]

1uf does present a problem and if space wasn't a problem I'd go for some large PIO vintage cap as some of them are very good indeed. The humble site seems to be ok and free of the hype that can surround these things and his recommendations are sound. You have of course read the 21 cap comparison that has been floating on the net and while it is far from perfect it is a good reference point along with the humble site and other feedback. I haven't heard those caps so I can't comment on them but you could always find some cheap Soviet stuff on ebay. The class capsule PIO caps are both small and pretty good (and dirt cheap) if you can find them in the correct value.

They are Vishay MKP 1841's that I used. I initially bought them as parts for my KGSS but since I buy a lot of extras I had some spare ones and a friend need caps in the value we tried them out and I was amazed at the result. They are certainly much better then the crap Wima is making so it's no wonder the Stax has been using them as couplers all these years even in the ultra expensive SRM-T2.

[humanflyz]

So I don't know if this has already been covered, but on Head-Direct's site, it lists the supply bias as 600V, so does that mean that if I use regular Stax amps with 580V that the phones will be under-biased?

[spritzer]

That's a whopping 3.33% difference so no. Such a small difference will not be noticeable. I'm much more interested in the recommended bleeder resistor as that might cause some compatibility issues.

[darkless]

What would you think would happen to the sound if the phone was driven by an amp with just a 500V voltage swing? We're talking about a difference of around 17%.

[spritzer]

You only need about 100-250v to get the phones to a normal listening level so 500v has plenty of headroom. These are all RMS numbers so peek-peek values would be higher. The bias voltage has nothing to do with the drive voltages other then that they have to be with in a certain ratio to function correctly.

[Dusty Chalk]

Also, the farther you get away from its optimal operating voltage, the less fidelity one gets. At 500V, you may or may not hear the difference -- I suspect I would, as I had problems with the O2's "waking up" (in my few auditions of those phones, under meet conditions, etc. etc.), and hated their sound until they got fully charged.

[spritzer]

That will only happen if they are left to fully loose all charge over some weeks. Then they will require time to spring back to life. The 500v he is referring to is driving voltage and not bias voltage.

[darkless]

OK, so there will be plenty of driving voltage. However, in my case there aren't any transformers anywhere in the amp, so I would assume that the bias voltage would be the same as the driving voltage, that is 500V.

From what I've been able to gather, the bias voltage is essentially determining "how far" the drivers will move to either side. How will a bias voltage of 500V affect the sound, then? I would assume that either dynamics and/or maximum volume would be affected to some degree?

Excuse me for being so dull, I'm trying to grasp some rudimentary electrostat knowledge here, I'm sure.

[drp]

Also trying to grasp rudimentary e-stat concepts and guidelines for suitable performance and gear matching.

So . . . how well would the HEV90 (or HEV70 in an extreme case), which I believe has a bias of 500V, drive the HE90 clone, which has a bias of 600V?

[spritzer]

OK, so there will be plenty of driving voltage. However, in my case there aren't any transformers anywhere in the amp, so I would assume that the bias voltage would be the same as the driving voltage, that is 500V.

From what I've been able to gather, the bias voltage is essentially determining "how far" the drivers will move to either side. How will a bias voltage of 500V affect the sound, then? I would assume that either dynamics and/or maximum volume would be affected to some degree?

Excuse me for being so dull, I'm trying to grasp some rudimentary electrostat knowledge here, I'm sure.

You don't need any transformers to generate the bias. It's almost always generated by a voltage multiplier which is just what the name suggest i.e. it takes any input voltage and outputs a multiple of said input voltage. The level of multiplication depends on how many stages there are. You can also just borrow the bias from the HV or B+ line as it's current is so small. I'm certain your amp has a 560-580v bias.

The bias voltage is the potential of the driver and it's voltage depends on the airgap between a stator and diaphragm. Stax used 200-230v for it Normal system and that has a distance of 0.3mm from stator to diaphragm. The Pro bias has a bias of 580v and a distance of 0.5. A keen observer sees that this isn't linear in the common sense and the reason for that is that the strength of an electrostatic field falls by the square of the distance. A closer space gives you more output at a lower voltage level but you get more excursion as the space gets bigger. Like everything in life this is a compromise and by studying ESL design you can know a lot about the design by simply listening to it.

When you go to a lower bias voltage you loose more potential of the driver so it's harder for the drive voltage to make the diaphragm move. Stax says that the sound will be softer and that's exactly true as the drive voltage can't control the driver as well.

Also trying to grasp rudimentary e-stat concepts and guidelines for suitable performance and gear matching.

So . . . how well would the HEV90 (or HEV70 in an extreme case), which I believe has a bias of 500V, drive the HE90 clone, which has a bias of 600V?

The HEV70 has a 540v bias but there are other factors here such as the bleeder resistor. This resistor controls the amount of charge there is on the diaphragm at any given time and it has to be at the right size for any given design as the coating material for the diaphragm will vary greatly. If HEAudio used graphite to coat the diaphragm then it will loose it's charge rapidly (relatively) when compared to the Sennheiser coating. That could cause stability issues but shouldn't really be a problem in the real world.

The effect of a lower bias will depend on the D/S spacing like I said before but the sound should loose definition and some focus.

[drp]

Thanks for the reply, Spritz.

Would too low a bleeder resistor value then cause a higher charge than the coating is designed to handle, causing premature wear (not to mention degradation in sound?)? In addition to sonic performance, I'd hate to spend money on gear (especially at this and higher levels) that degrades more quickly than if better matched. I've always wondered this about driving, say, an HE60 with the KGSS or other non-Senn amp... 8~)

Not that the lucky few that own the HEV90 would do so, unless their HE90 became unusable, but I was also wondering specifically how an HEV90 would drive the HEAudio? Additionally, how the Aristaeus or other HEV90 clone would drive the HEAudio?

[spritzer]

A lower resistor would possibly lead to arcing and if something does go wrong it is there to protect you as it burns up with very little current going through it.

The HEV amps are not matched to the HE phones in any way. The only way an amp can hurt ES phones (ESP's?) is by arcing them with too much output voltage. That simply isn't going to happen with any of the amps currently avaialble.

The HEAudio 1.3 is in no way, shape or form a HE90 clone so they shouldn't be compared like that. The construction is very different and it is hard to speculate about them unless I have spent sometime with them here and disassembled them.

[drp]

.......The HEAudio 1.3 is in no way, shape or form a HE90 clone so they shouldn't be compared like that.

Mindset recalibrated

The construction is very different and it is hard to speculate about them unless I have spent sometime with them here and disassembled them.

Disassemble Johnny Five?

"Escaped Robot Fights for His Life. Film at Eleven." - Number 5

[spritzer]

Mindset recalibrated

Much better! I can understand that they are a bit sensitive about that as something original that is made in China is quite rare indeed.

Disassemble Johnny Five?

"Escaped Robot Fights for His Life. Film at Eleven." - Number 5

Rip apart and modify... Depending on how the new ones will turn out I think there is some ground for improvement... maybe quite a bit even.

On a side note if there is some thing not clear about the ES principle, ask away.