spritzer

For me the first models are the best.

They are SZ1's and what was actually wrong was never confirmed. Most were bad enough that they were repaired immediately but some slipped through. Some of them just sound "off", not as smooth as the Mk1 should be and with overblown bass and treble issues.

Why am I not surprised it is custom. I'm always up for some trading as well. Well that's where it gets tricky as this varies quite a bit. The spec for Stax states the 100Vrms point but how they get that figure is unknown.

It's not really about listening at insane levels. We were well aware that an amp like the KGSSHV and T2DIY can and will burn up a Stax transducer if it were ever to see the full force of the output. Not likely to happen unless somebody were to feed it from a high gain preamp but it is something to think about. That said the amp is then just idling at normal levels so there are clear benefits to using crazy voltage levels.

Not a whole lot of headroom with 300V.

The 6C4C is at least cheap so the voltage limitation is less of an issue. You know me, I have very little willpower when it comes to buying parts... Do these have a 6db gain tap on the primary?

We are indeed alive and well, just sidetracked by some other projects. I might also add a TVC to it for MOAR transformers...

I don't think there ever was any Germanium sand that could handle 1500V... My plan is for a spud electrostatic amp with just two triodes and DHT's at that. I know ETF.12 had a competition along these lines but I'm going to be far stricter to myself. No push-pull, current sources, parallel tubes etc. Just transformer, triode and transformer...

Ohhh it is a poor idea. Building the B-10 was a poor idea but I did it anyway. The 300B is linear but it is limited in terms of voltage so you need output transformers. Costs are starting to mount to say the least at this point. I'm doing it though as I like to build crazy things and I have some 300B's here. This is my version of spring cleaning... While on the subject, an even crazier amp design crept into my head this morning which will be even more expensive and ludicrous.

More voltage swing is a good idea generally but there are two things to consider, the sensitivity of the drivers and the absolute max voltage the drivers can handle. Now these get plenty loud with just 100Vrms so the idea of more voltage swing is more about clean power than anything else. The second limit is the absolute max voltage the drivers can take which is roughly 1200Vp-p. This is even lower for the Senn HE's but again, this is very, very loud. I don't think Stax ever used graphite on the diaphragms. No way it would have lasted 50 years on my SR-1's...

Where did the EL34 break? This can point to what really went down. Still, a burst of air into a tube running this hot will make it into a very nice lightbulb... Ehhh a quad of 300B's is too rich for my blood. If this one goes well then I might try something like triode strapped pentodes at higher voltage. 7403's would be very interesting due to the high voltage and dissipation properties...

I guess it is possible but I just don't get why you'd want that. Varying the bias voltage isn't a good thing in my book especially with the charging issues that come with high resistance.

Yeah this is a generic part so any manufacturer will do.

Fuck yeah!! Dissimilar EL34's FTW. I've been distracted by other projects so this one is on hold for now. What can I say, I have a problem taking on new projects such as doing the WES/Electra class amp properly with full bandwith and so it can accept SE inputs. Then there is the single ended Stax amp... 300B's!!!

It's easy enough to calculate the electrostatic force if you know the D/S gap and the bias voltage. Basically it falls with the square of the distance which is why we used 230VDC for a 0.3mm D/S gap and 580VDC for 0.5mm. Go up to 0.7mm and we have at least 1100VDC. If you were to drive both the stators and diaphragm with signal then you would end up with a bunch of distortion (at least by ESL standards). The best way to get the super low distortion of Stax drivers is to run the diaphragm in constant charge mode. That means high resistance, very high resistance. It is possible to make pretty much anything work though.

If this trend continues then we are indeed looking at just tubes for high voltage use or stacking lower voltage parts. One HV transistor that is cheap and easy to source is the Fairchild 5027 but the gate capacitance is quite high...

I wouldn't touch the bias. Very little gains from about 2-3% increase in the electrostatic force.

2SC4686 is EOL as well. Fuckers...

The best alternative would be the 2SC4686 which is the same part with a lower voltage rating. Still in production last I heard. No problem. The switch PCB's should be here in a week or two so drop me a line then.

Most of these switches can indeed handle 5A/250VAC but sometimes you have to track down the manufacturer and the actual spec sheets. Sure, I bought 100 of them... They were on the expensive side due to the routing required but it wasn't too bad. I also have pcb's for the Alpha pot, pots too and the teflon Stax sockets should anybody need them.

I always get dual windings as well. I can't see any downside to it. Well I bought a pile from them so I still have some but I also bought 50 more from Alibaba. I might have a problem with stockpiling stuff.... I also just ordered some PCB's for these switches to make them easier to use. Built in spot for a resistor to drop DC voltage higher than 12V etc. Now I'll get back to designing the PSU for the single ended Stax amp...

I vote for some blutac to be used... and Dynamat.

Yup, I always use latching switches on my amps. I like the simplicity of mechanical things...

There was a spout of driver failures for a while but mostly they are just inconsistent. Some are good while others are not so. Perhaps Stax were tinkering with the drivers before the Mk2 was released, who knows...

They were Mk1's.