spritzer

Indeed solid thermals shouldn't be a problem for a good soldering iron. A good Weller or Oki isn't that expensive and makes soldering so much easier.

The 303 mod gives you the best of both worlds, a kick ass Sigma and a normal bias Lambda. Pure win!!!

We need to make one for the KT120 biased at half power... I do think that the EL34 is the best bet and there are no triodes which can handle these voltages and don't cost a bundle. DHT's also bring even more filament hassle and multiplies the cost. The 6CA7 was an attempt to make the EL34 without paying royalty fees to Mullard. They are pretty much the same. I am indeed out of the Alpha pots but I might do another run. Too busy to even think about that now... What's been going on lately is that we are looking at pretty much every possible way to design a Stax tube amp and designing circuit boards so people can actually build them. The board files will be made available so these amps can be built by anyone.

Love the name.

Pffft... start with the name and demographic then work from there...

The THD is on par with the 727 so not bad for a tube amp. Tube matching is critical so matched octets would be a good idea. This could be the simplest high end amp anyone can build. The PSU is complicated but it's also pretty forgiving of mistakes so it would be a good noob amp. I do think I could cram the amp section in a 1U chassis but it will not be easy... As for a name, well we'll have to think about it...

We could arrange the ecc83's in a line in front of the EL34's but I'm too lazy to do it now....

I can just see me ordering a transformer for this one... "You need how many 6.3V windings???"

What can I say, I'm a glutton for punishment. Plus it's what, 300$ in parts plus chassis? Not a whole lot... As for the SRPP, Ray has said many times that the amp is indeed SRPP and it is wired for SRPP. As Kevin said, Broskie would not agree though as the circuit will not behave as SRPP with an electrostatic driver as the load. We countered this by placing 1M resistors to ground after the output caps which will diminish the impact of the wild impedance swings. Not a perfect solution though.

We do have trouble doing something simple. Adding more parts, stages and power supplies is often just the most simple solution...

Yeah, just cut the component leads and them desolder and clear the holes. If you really want to remove the sinks then an OKI/Metcal iron is your friend. A few seconds and they are loose... Ohh and I do it by heating one joint, edging that out 1mm or so, then the other joint until it's free.

The black color is often carbon and that + HV don't mix.

The B-10 was a semi difficult birth over the last few days though most of the issues were linked to the new "super simple PSU" I drew up for the amp. Nothing wrong with the basic design, I just made too many layout mistakes but it's all good now. The only issue with the amp was tracking down the source for very faint hum. I did succeed in finding it and now it's as quiet as a solid state amp. Not bad for a cramped 1U chassis, shared umbilical cable and very hungry tubes (roughly 4A for the 5687's). My only real goal with the amp was to see how hard I could push the tubes without them either imploding or the plates catching fire. The max rating for 5687's is 4.5W per triode or 7.2W for the both of them. Even at 9W for each envelope I had no issues but I backed off to 6.9W or so as these ratings really shouldn't be exceeded in a long term setup. As it stands now the B-10 is identical to the A-10 except where part changes made sense and naturally it's fitted with a much better power supply. Here is a list of the major changes: -Volume pot moved so it's in front of the first stage, not after it as in the A-10. I added 500K grid resistors on the "lower" 5687 triode instead of the pot. I don't need to fool myself that this amp is noiseless even though it really is. Dead silent even at full volume with the super sensitive SR-003. -Separate filament winding just for the 5687's which has the center tap connected to the +300V line through a 100K resistor. This is a major change since the A-10 uses two parallel connected switching supplies to run everything, tube filaments, relays etc. with the - side grounded. With one cathode in the envelope sitting way above the cathode-heater level this is downright dangerous so a floating winding referenced at +300V gives me trouble free operation for most of the output. Only at full voltage swing will I run into issues so it's not perfect but a huge improvement. -The front end it fed of a fully regulated DC supply using it's own transformer. This also drives the LED's and is a large factor in the zero hum. -Some modifications were made to the circuit so it sees a more stable load and thus behaves more like a SRPP circuit should. Ideally they should see a fixed load to behave but electrostatics are anything but that so a bit of counter balance was added. Despite all of this it is not a very good little amp. Bass is lifeless and flat, top end uneven at best and all those lovely distortion molecules... It didn't like a loud session with some metal one bit either, audibly clipping into a Lambda Signature... Still, one could do worse for the 500$ or so this cost me to build. One could have paid Ray 6.5K$ for one which is even worse...

There is a difference but the KGSS still holds its own. It's warmer in tone and more forgiving than the HV. The truly interesting comparison would be to use the stock KGSS circuit with the HV PSU and running at a higher voltage. This is how the idea for the KGSSHV initially started so I'm going to build one soon. I'm also building one with different output devices but running at +/-350V to see how I like it.

No pix I'm afraid but the glue holding the damping wool has clearly perished. The driver should be visible with the damping resting on the edge of the it. .

I clearly need to add some gold paint then....

The BATE is pretty much what we have in the schematic above. Parts of GES, parts of the ESX all mixed in together. The B-10 is my take on the RSA A-10 so improved and made safe but the basic circuitry is still the same. Looks something like this:

What's missing from the schematic would be the wattage of the EL34 cathode resistors. While all the other resistors are 1/2W these need to be larger.

These amps are designed for the ca. 120pf load presented by a Stax driver but some can drive tougher loads such as the Floats but I wouldn't venture any higher than that. The voltages we are working with are also miniscule compared to the drive voltages inside an ESL. We have been prolific for the last few weeks discussing new designs and how to rework old ones, amps and power supplies alike. Who needs sleep anyway... Given this is where it all started, the B-10 will probably see the light of day this weekend (barring any late cake orders...). The amp section has been ready for weeks but Edcor took their sweet time with the transformers. Massive distortion here I come but it will be as good as this circuit can be made.

I love fiber...

They have very exact standards those Germans...

That's looking good. Getting the mix right is half the "magic" and so is the duration of the mixing. The machines we use have two speeds so for a normal medium density bread it's 6 minutes slow and 3 minutes fast if using the German spec 550 flour. If using any of the French flours or the American variants then the times will be rather different and often unpredictable due to the high gluten. I did give mixing by hand a try over Easter and it is possible but rather time consuming. Took me about 25minutes for 1/2L of dough (1.4kg or so) with no tools except my hands. It was fun but I think I'll stick with my machines...

I was more commenting on "speaker like" presentation of the Sigma's which the Floats are also trying to achieve rather then the actual performance. If we go by that then none of the Floats even come close and only the K1000 makes an honest attempt. For me the Floats were all about impact which probably stems from using speaker drivers in the earliest versions. High voltage swing with high bias to get better dynamics. I don't know if what you heard were issues with build quality but they pretty much match my experiences. It also matches the figures as with an open baffle the bass is the first thing to go and the treble becomes more pronounced. There are some clever ways to get some of that bass back but the lack of earpads will always cause issues.

What exactly was I wrong about? Look at where the Jecklin design came from, or more importantly the drivers, and there is a whole lot of room for improvement. As for Stax not sounding natural, you are joking right? Which set and with what amp would be a much better question. If the Float sound is to your liking then it has to be a Sigma, preferably a Sigma 404.

I've been following the German thread but I'm not impressed to be honest. Sure, it may be an improvement over the PS2 but that was far from being a top end set to begin with and things have come a long way since then. They changed the connectors simply because Hirschman doesn't make them any more so it was a necessity but the cable looks like the same design. If any headphone would benefit from a lower capacitance cable then it would be those huge drivers... I don't think it is possible to run these drivers at a +600V bias in the open frame. The backwave issues are huge and the only way to overcome them is with brute force. The PS2 ran at +1200V if I remember correctly so these should be similar but more importantly the drive voltages are far higher. While Stax transformer boxes use a ratio of 1:25 for stepping up the voltage, the Jecklin boxes used 1:125. This poses a problem with Stax compatibility even though amps like the BHSE and KGSSHV should have no trouble driving them. These are all issues which we came across with the Purtscheller design ideas back in the day. He was going to offer a matching tube amp but with no Stax compatibility the design was doomed. The days of matching phones and interface devices are long gone and we are only going to see a further move towards the Stax standard in the future. To me this set looks like the old PS2 drivers in a slightly better chassis and with a better headband design though mostly borrowed from the PMB500/1000. Sure, they might sell a few sets but nothing compared to what they might sell with Stax compatibility. I do think the drivers could be redesigned to work at the lower bias and voltage swing ranges but it would take some clever baffle design and at least partial earpads (like the PMD's). This is no longer a niche market as can be seen by the hundreds of Stax SR-009's sold in just one year...