spritzer

I hope you aren't using the TRS plug with the t-amp as they really don't like a common ground. Same reason why the WEE should never be used with a bridged amp...

The 2SA1831 is 1/3 the price and should also work. It's not isolated but no heatsinks needed here. Since this is the "something different" thread I've stumbled over an even simpler and crappier way of doing the Darkstar and it's all on one chip. Stay tuned for what will probably be the worst amp I'll ever build...

I'm always a fan of using up some of these 2SA1968's...

Whether the transformer unit is self bias or mains bias should have effect at all. The power needed to energize the diaphragms is so tiny that a bit of leaching of the audio signal won't matter. That brings us back to the age old issue, amp vs. transformers. The amps have their own set of challenges but high ratio transformers built to a small price will always be a problem. The cores are too small, the winding setup is too simple and the layout inside the Stax boxes isn't doing the sound any favors. Amps all the way for me but there is also something to be said about the simplicity of transformers...

Given that none of us can agree on attenuators I do think it is best to keep them offboard. I certainly wouldn't be caught dead with an RK27 in this amp... When I have a bit of time I'll order boards from me and KG so we can test the beast.

Happy birthday buddy!!!

Yeah, that's pretty much the only solution I can think of. Well that and buying a smaller head as my more petite friend just loves how the 507 fits while it was a torture device for me.

It's just been postponed as there wasn't enough headroom for the feedback. We never release anything unless it is perfect unless "sounding like crap" was part of the plan.

I tell every noob to just buy an OKI PS-900 and skip over the cheap stuff. I'm all for using cheap stuff where you can get away with it but cheap soldering irons are just that, cheap. Only exception would be the military surplus stuff Kevin brought to CanJam.

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....