spritzer

You only need about 90-100mm in height so 3U is plenty. This one was built into a 3U chassis: I'll take better pics when I prepare to list it for sale (only need one amp here) but there is a lot of room in there. That chassis is 300mm deep which will work just fine with the KGST power supply. It's just slight bigger than the one I used in that amp so we could use larger capacitors (in diameter that is) and put proper heatsinks on the 10M90 current sources. Yup, this one is running at 400V and sounds just lovely with RCA tubes. A slightly different take from the KGSSHV and it's fun to compare it against the mini KGSSHV given the similarities in PSU, voltage and power. The servo settles at around 2V for one channel which is good as I could just manually adjust it to 6V. The other one hovers around 0V. Not bad at all...

I see your very pretty sunset and raise you some midnight sun high in the north sky: I took that on Saturday morning on my way to work so roughly 4:10AM. Simply too pretty not to capture even if it was just on the iphone and I was running late...

It's also possible to just use the chassis as a heat spreader to a sink close by. We aren't talking about too much heat here...

Happy Birthday Greg!

It's very stable once it's warmed up. Tubes vary though so adjusting the series resistor to the pot might be needed but that's true of the KGSSHV as well.

Here is the second KGST up and running. I don't recommend trying to build it this small... This one was supposed to be silver but I ordered the wrong chassis though I think it looks kinda nice. The transformer is the BH unit I was having trouble with and here it doesn't complain at all. The amp is drawing about 65W which is a far cry from the 170W or so from the Blue Hawaii. The real problem with something this small is the height. The tubes are simply too tall to use an 80mm chassis but I got away with it by hand selecting the shortest tubes in stock and using 6mm standoffs. This one also uses the KGSSHV mini PSU which is considerably smaller than the KGST unit. Just noticed that there is a typo on the back panel. Bloddy "electostatic headphone amps"...

I use a SR-207 but any of the electrets are handy to have around. No need to worry about the bias supply then. It's not a design flaw and all electrostatics can suffer from this. You need the diaphragm to be high resistive for the drivers to work in constant charge mode but this opens up the possibility for other sources of said charge. The SR-009 stators are rather heavy so mix temperature variations, static, humidity and you end up with problems. That happens as the glue that holds the drivers in place weakens over time. If the driver hasn't split open then you are good to go with simply applying new glue pads and put the driver where it belongs. It's backwards as in the mesh cover faces away from the ear? That needs to be made right so just use a knife to pry the driver gently off the baffle and reattach the right way around.

The board was a cleanup of some old board design which had the error to begin with so it just continued onwards. I'm cleaning up my huge stock of K170's so I didn't try the LSK389 until yesterday and then it issue was clear. That plus one mislabeled transistor and some component fit issues is not bad at all.

Nothing to sort out, short of discontinuing the 009.

The cracking is a good sign. If a cake or bread doesn't crack then something is very wrong.

Quick update, PSU has been tested and it works perfectly. We discovered a small issue with the amp boards but it's been fixed now. Kevin will fire up his ST soon and then we can move on with this.

It doesn't make any sense to use a PSU that is not better than the KGSSHV unit as you'd just degrade the performance. Dropping the voltage with a resistor for the front end doesn't have that big of an impact though. For a transformer you might get away with an oversized 230VAC unit. The margins are very small and I'd use a 250V unit instead but it could work without dropping out of regulation. The SRD's use an input limited voltage multiplier. It can't take any load though which means they are all but impossible to measure.

Happy Birthday Justin!! I hope you got something nice like an Audio Precision workstation...

Yeah, it's just those two boxes glued together as they don't even share a power transformer. Also the XLR inputs on the back aren't balanced at all so bone stock ED-1 and SRM-1 Mk2.

That's how we roll...

Yes but it's not something I'd ever eat. It's a hodge podge of soy, wheat fiber and starch.

Yup if we go that high in current. No way we will go higher than say +/-450V on it.

I'd stick with the stock CCS but it can be modernized with new sand. The TOGTE uses stacked devices and both NPN and PNP. Speaking of sand, this is a pretty sight: That's enough for a few HV's...

Going by the sugar content, that is more into cake territory...

That was too funny, 5% distortion is good enough...

The output voltage is a problem but it's just goes hand in hand with the bad engineering. This amp has a total of 6 triodes to generate a four phase output at a gain of at least 500. This really isn't enough and you would need a bunch of transformers to help out. That brings its own problems and adds to cost which could be avoided with good engineering. Not enough voltage swing, clearly very high distortion so hardly fitting for a transducer that runs at about 0.1%THD. About the simplest tube amp there is would need 8 triodes even if it was single ended only. Now the output tubes are max 300V units hence the low output voltage swing but why not use 6SN7GTB's which can take 450V and run off +600VDC? Much more voltage swing which is actually usable. As for amps for the 407, they are not the nicest sounding set Stax have ever made so even something like the 006t would work. Should help with that glaring top end.

I just bought a bunch of tubes off ebay and it was... interesting. I bought close to 100 units and many are great but some are just crap. Some are even original factory rejects...

I had 20 minutes to kill... Haven't tested it yet so hopefully soon.

This was posted on the other side, HAD AudioLab Maestral 4STAX... http://www.had-audiolab.com/products/power/maestral-4stax Has to be the crappiest name ever and that amp design also has to be the worst anybody has ever thought of. Why do all the Euro amps have to be shit?

Yup, black plate is RCA and gray is GE. I have some RCA here that are gray plate though and then we have the Japanese versions.