spritzer

Very nice Michael!!

That's what I was planning to do, running every tube off its own PSU. The cost isn't really an issue here but I'd like to use DHT's that are relatively cheap which the 845's aren't NOS. With my headphone collection almost complete it's time to build an amp to drive them all.

Ahhh since its in US$ you get payed by the seller to be rid of them...

The 807's aren't cheap, they're dirt cheap. I bought them to build a cheap P-P speaker amp that could serve as a Stax amp but now I'm tempted to test them in the BH circuit... \

Wuss... I like the Furutech products a lot but since I'm going SE only in the future WBT Silvers it is.

If you want the best and are willing to pay for it look here. They can make the connectors with silver pins if you have the cash.

Thanks for the info. Have you been buying some RK50's?

I'm always ambiguous... The EL34 is far from being the best pentode out there but a Mullard XF2 is a force to be reckoned with. Expensive as hell so I'm all for a cheaper type that sounds as good so please do some testing... since I can't be bothered to butcher my BH. Btw. Kevin have you finished the 845 based amp circuit yet. I'd really like to see it when you do.

You certainly could alter the circuit a bit and install different tubes but none of them sound as good as the EL34. Since we are on the subject of pentodes I just bought a quad of JAN 807's and I'm going to see if I can't throw something together.

That's just too cruel to say...

If it is French then I'm going the other way... ....

They are both loud acoustically and contaminate electricity in a very bad way. That has to change before they can start to gain some headway against the silver disk. It could be possible to use galvanic isolation and create a clean room inside the computer before the signal is lifted out and have the computer on a different PSU...

Whats not to like, huge DIY tube amps and Quad ESL speakers... my view of heaven... :'(

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. 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.

It's very hard to beat the direct connection to the drive especially if crap like Toslink is used. The upcoming APL DAC will have some propitiatory link to a from a modded transport so if they can do that in some PCI card then it would be awesome. The horrible environment of the PC is still to be dealt with but an external PSU for the PCI card could be an option...

ETF is one of the few audio shows I'd like to attend. Lats year some engineers at Philips recreated the original triode to celebrate its 100. anniversary and they even built an amp around it. Way too cool!

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.

Some are more complicated then others. The whole fault with Sony units was a horrible output stage and some questionable things on the dac boards. A normal eXemplar or Modwright mod is a new clock and outputstage with a replacement of a number of components but it's pretty far from a complete redesign. They still do solid work at a lower price and that is to be commended. Some of the other modders... are more questionable. I can't wait to get mine... This is certainly true as most modders are spread very thin with a lot of different manufacturers and not very many units of any one kind but APL stopped doing that a long time ago. If my Denon will need to be repaired it will go back to APL. I know they have been replacing drives and all the usual stuff that fails and they will continue to support it. Some of the modders aren't as helpful to say the least...

Going with those comparisons I've read they don't stand a chance. They are after all simple mods while the APL is a complete rebuild. Why on earth not? You get much better service and better bang for your buck. The product is never outdated as if there is a new version you just send yours in to be updated. The APL gear isn't really a modification as they are working with Esoteric so i would much rather call it a rebuild, doing things Esoteric could never do and stay profitable.

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. 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.

Just buy an APL player and be done with it. You can have a digital input, volume control and a universal player that plays any of the old formats. I don't quite know what the price and features of the newest players but you should drop Alex a line. The guy who sold me my APL 3910 compared it to a dCS P8i and ARC Ref3 line stage (the APL has a built in volume control) the last day before he shipped it out and the other gear was blown away in every aspect. That's 25k$ against a 4k$ player and it's not even the newest version. This was in an email sent to Alex and not me where the seller said he was nuts for selling me the player and he wanted a NWO soon. Now mine is even better with the new AKM 32bit.

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.

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.

Ahhh no,no we are talking about two totally different things. I thought you wanted to connect a Stax trafo to the tubes but I now see it was a result of me being barely awake. All the amps see with a Stax trafo is a benign 8ohm load but the transformer turns that into the 5kohm that electrostatics like (transformer ratio 2*input impedance) as well as stepping up the voltage and reducing the current.

I wouldn't connect them to a Stax transformers except maybe the other way around for a cheap/small/crappy output transformer for a push-pull amp. If you were to connect it before the output transformer of a SET amp you'll end up with a 1:25 step up of the output voltage of the tube. The output transformer steps down the voltage, impedance and steps up the current for dynamic speaker use. You can connect Stax phones directly to the tubes through a capacitor, no transformer needed. You will need some load on the tubes to make the amp more stable but thats given.