spritzer

There is a bit more to it than that. Sure the diaphragm is a factor but so is the stator design, how the whole assembly interacts with the chassis, the distance from driver to the ear, the earpads (major point there) and the disc behind the drivers as is reflects a tiny bit of the backwave.

We just added some extra supports to the HVk...

Old Stax did get lost a lot too in technical BS and make something that wasn't so nice. Their improvements were always that.

They need to be high voltage rated, power isn't a problem. 1/2W is fine as most are rated at 500V.

Not really, no. It's well within spec.

You need to jumper the 270V zeners, not just leave them out. The Vishay 0 ohm "resistors" are good for this. Wire also works but insulation would be nice. Wouldn't be the first time just this past minute...

Great post Frank. AC filaments are indeed black magic at the best of times and it can take a while to master it. Normally input tubes are more susceptible to hum as they are high gain so using DC for those and AC for the output is also a good idea. When driving heaters with DC it's also wise not to get hung up on trying to drive them at 6.3V or 12.6V as running them in series saves current which is heat, often quite a bit of heat. You should also not be afraid of building sub assemblies for the complicated bits which can be added to the circuit. On the WES style amp I did that to save space and fit pretty much the entire front end on one 8 pin socket adapter PCB. Agree fully about the 9 pin sockets and they are a pain to work with. One of the main reasons why it took me over two months to assemble that GES I linked to. Tiny box with not a lot of options meant a lot of frustration over how things would fit.

19" 2U, 350mm depth.

First KGSSHVk up and running... This is a 450V version and sound bloody good...

It isn't.

Happy Birthday my friend!

They have T2's plus a host of other setups. Perhaps we should send them a Blue Hawaii...?

Polystyrene caps.

There is a huge market for tubes and it is growing larger by the year. I really don't see ECC83's and EL34's ever going out of production unless people stop liking guitars. That said, some of the production values are piss poor and for me the worst offenders have always been Shuguang and New Sensor.

The only thing I'd ask for are slightly thicker boards. The bending on the KGSSHV amp boards is a bit too much from the old batch.

You are at the right place and we can only wait until our member Kerry sees this as he might have some PCB's. He did the only modern version of the BH which has both the PSU and the amp section updated to accept 10M90's instead of the 2SA1968.

Some of the modern tubes do rattle a bit but they really shouldn't. Shaving down the materials used is the best way to make money on tubes these days.

They are made by IAG, the Quad parent company. Well they market them at least... That is a stunning build Frank but the 'stat amp you had next to it had some ghetto charm. KGSSHV boards will work but you need to relax the current limiter a bit. Andy used one in his ES-2 and ran into trouble due to the higher current. I used to enjoy P2P but today it's just so much easier to sit down, design a circuit board and have a few of them made. The sub miniature amp took about two hours in total to layout and double check. That's including checking Mouser for the correct part sizes etc. I really should just redo that board with the larger 9 pin sockets and bigger caps/resistors for a simple GES PCB...

The only PSU boards I have are my shrunk version of the BATE PSU, a simplified version of the T2 supply. Might need to tinker with it a bit to get it work at these current levels though. They should use 6SL7 and EL34.

That tells me nothing, what were you measuring to get a result of 500-700? You should get the voltage drop of the diode.

Yeah and even so you may load the voltage divider and/or the doubler so no way to get a good result. An offset/balance drift of less than 5V is nothing to worry about.

The GES is a lovely amp but I would second Ari's recommendation for the ESX. Simply a better circuit and easier to build. Here is my old one: http://i.imgur.com/qzdT4ws.jpg Forgot how colorful it was. Here is my balanced GES: http://i.imgur.com/8ZDDx.jpg http://i.imgur.com/4n24s.jpg It's very cramped as the box is tiny and I wouldn't recommend doing that. Going ever smaller leads to more and more complicated solutions. Then there is the option of combining the two circuits... http://i.imgur.com/oGWCd02.jpg ESX front end with GES style output stage.

Dust is a problem at 700VDC but I bet this is just a tube issue. I would change the caps though...

No problem posting it here but the basics are simple enough. Do a diode test on all the transistors to sort out obvious shorts and then compare the voltages between the channels. It is a very nice headphone, lacking in most areas but it just sounds right despite the shortcomings. I really have to get that really old one I found shipped here as it might be a 150V version... The BH is already set to 230V so it's all good.

A few things to try, are all the LED's in the circuit lit and have you swapped the tubes or replaced them? How is the offset/balance?