spritzer

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.

In total there are at least five versions of the 007. Here comes the list but the serial numbers are just approximations. No idea when the actual change took place. 1: 70xxx serial number, first version with the large frame drivers and carbon fiber case. 2: 71xxx serial number, simplified driver frame for easier assembly, new materials on all "soft" parts 3: SZ1 and BL version: Some small changes around (cable entry for instance) but the biggest problem was the QC with these so the sound is hit and miss. Mostly miss compared to the first version. 4: SZ2, the first Mk2/A units. New earpads, headpad, cable entry. Earpad spring is raised to help comfort and a port is added to eliminate the fart. The drivers are pretty much the same as Mk1 so these can be modified. 5: SZ3, identical to the SZ2 but new diaphragm material and the port has been improved. Introduced in mid to late 2009 and the model in current production now. No hope of rescuing these through mods.

It was Stoli and cranberry juice mixed roughly 50/50.

Yes, that's the Stax way of making gray market products stand out.

I don't have any Amphenol jacks left to check but the picture is correct for the outside of a chassis. I have one of those on my wall...

Yup, the SR-007A.

Most excellent Deepak! Should be something new coming to the 'different thread as I'm looking into improving the WES design. By improving I naturally mean throwing most of it away...

Nope, it comes from Sennheiser showing and auditioning a prototype at the international distributor meet last year. That event was meant to show the distributors what R&D were up to.