spritzer

The root cause of this are the origins of the Exstata design. I was there in the "super secret design forum" when somebody linked to the High-amp.de site which features a design shockingly close to the SRM-1 Mk2. Things spun off from there but with that basic blueprint there are only a few ways to go to improve the design. Different ways such as using zeners instead of resistors (not a good call IMO due to the noise) but the end result is the same. There is a problem with this though as some of the finer points of the design become lost in the translation which is why for instance the Exstata sounds a lot worse than the SRM-1 Mk2 and the measurements back this up. Same problem with the ES-1 amps. Mikhail was working from a schematic which didn't feature the heater wiring and I'm sure he never spent a moment wondering why Stax used unequal rail voltages (+250V/-350V)... Now for the LL, why on earth is he using mosfets instead of BJT's? They are far worse but it does take some experience with 'stat amps to know why. I've been having some problems lately sourcing high voltage TO3 BJT's to repair my old Stax amps. I can get some old stock at lofty prices as these haven't been made for at least 20 years since the world moved to to220 but this isn't really an option. Now what I can get in ample supply are mosfets but they all have the problem which makes them unsuitable for this role, high capacitance. Same thing applies to the LL, they may give you a certain sound signature but I for one think amps should be as neutral as possible.

I thought this was given in the same fashion as some Stax models have a midrange resonance while others don't using pretty much identical drivers. Being harder/easier to drive means nothing in this regard.

Knowing Kevin he's not too worried about it being kosher or not...

Yeah that plus people not knowing what they are doing. Vishay is basically an umbrella for everything now but they do own BC (aka Philips) so that opens up a lot of good stuff. These are the ones I use: http://www.mouser.co...XoJNmZF%2flI%3d

Yeah but things add up once you build too many to count...

Why are people using CMF60 resistors for the bias ballast? Doesn't anybody read the bloody spec sheets?

Improved version naturally. Fits well with the Exstata V2... Onboard sinks too. Hey, I quite like those amps given how small they can be made. I'm building one now into a SRD-7 box for the smallest fully balanced amp I can make. That would be marzipan or rather persipan in most (not pure almonds but cut with apricot kernels). Lovely stuff we use to make cakes up here mixed with 50% sugar and a bit of eggwhites.

Happy birthday Fitzy!!!

Looks like fun!

Let's just put it this way, there is a reason for the pile of amps, dacs etc. in a spare room.

Yup, I get regular care packages from Kevin.

Things are indeed getting bad but we can only hope that there will still be some demand for high voltage BJT's. The IXYS part is available at Mouser, you just have to search for the TO220 version (P) and not the SMD (A). Naturally not available outside of the US...

Yeah, Kevin has been working on a KGSSHV setup sourced exclusively from Mouser and that uses fet's instead of the BJT's.

Very nice and now my Mouser is in Swedish. Seems appropriate since I just got off the phone to Sverige....

Not a bad price at given how much people are willing to pay for fubar sets. As if there was ever any doubt but the 007 Mk1 sounds great with the KGSSHV.

No veil in my rev.1 either or reverb or anything like that. This is mostly linked to amplification used as the "ortho amps" over on HF are almost all ehhh... lacking in true power delivery. I do think the LCD-2 is a very nice headphone but it's never great, similar in many ways to the HD600. Does most things well but they always fall a bit short in absolute terms.

Amazing similarities but let's see how Stax did it in 1982: and the 323A:

Even HE-5's? Those are truly awful...

Why are they painting old hookers? I think the fumes are getting to 'em....

Measuring anything while in circuit is always a crapshoot. Way too many variables to list. While we are on the subject, the HV sounds fucking amazing!! Who stuck a subwoofer to my 007 Mk1's?

The output on the stators is AC but the polarizing voltage is DC. The only thing the bias does is to set the potential of the diaphragm so it can be pushed and pulled by the AC voltage on the stators. The ballast resistor for the bias supply is used to set the diaphragm to constant charge for lowest distortion but in reality it acts much more as a safety feature. The diaphragm is an open circuit in essence so if something were to close that circuit the ballast resistor would drop most of the voltage. What you are doing is something rather different and those 10M resistors are used to balance out the output stage and to drain the output caps.

This should help... http://i.imgur.com/xgvci.jpg Not small... Edit: Yeah I went utter overkill on it. Some Loxeal too just for good measure. Yup, BHSE castoffs. Having the same knob as Steve is just the icing on the cake...

I wouldn't bother with those resistors and keep the 5M resistor as well. It costs nothing and if something goes horribly wrong it will kill most of the bias voltage. I would place output resistors (5K1) if you want extra protection but there is no need for the 10M units.

I don't think messing with the current on the onboard sets is a good idea since it is hot enough as it is. Now with huge offboard sinks then the sky is indeed the limit and I'm going to go damn close... Now if somebody can spot my way of dealing with the 10M90 sinks with only metric screws at hand...

Proof that a 2U is all you need... It's running in that pic, I just couldn't be bothered to hook up the indicator LED. This was a difficult birth though with an intermittent pot in one channel and the other was just fubar. I swapped pretty much everything and it still didn't work so I finally gave up and built a new channel. That one also needed some work to get right. Still, build enough amps and once in a while one is bound to be like this.