spritzer

No tubes and nothing is set in stone as of yet except that it won't have tubes. We can call it a mix between the KGSSHV and the KGST.

If you want to run it at +/-400V then you need 325-335VAC rails. 280VAC for +/-350V. For current 110mA is sufficient but I'd shoot for 140-150mA to be on the safe side. 30-36VCT is about 500mA. Heater windings should not be CT as they have -400VDC floating on them. You have to have two heaters or you will have massive problems so one for each board. 1.5A is more than enough to account for the variables in the tubes. No soft start for me as I simply don't think it is needed. The tube won't arc at these low voltages.

I've had two SumR self destruct and it ain't pretty. Speaking of transformers, seems Keen Ocean didn't quite get my requirements. The one in the middle should be about the same size as the ones on the left... KGST transformer on the far right, each weighs a whopping 3.3KG...

Are you running 10M90's at 500V in the KGST? That's not the best of plans...

The plus side is also how cheap it is to build and everything is in current production. No SMD parts either as the voltage is low enough to use KSA1156's and Antek transformers will work perfectly. A pair of ECC99's is about 35$, 12BH7's less than that and 6N6pi's way less than that. I also bought some parts to try a KGST with current made tubes.

It's also hard to be negative about anything if you lack the basic brain activity to understand any of this. I think it is the true mark of stupidity. It doesn't even work in Icelandic where word order is pretty much free.

The real problem are the tubes as not many can handle more than 300V. Push them hard and it all falls apart... The only dual I can think of that is rated for 500V is the 6CM7 but it's a dissimilar triode so not suitable for something like this. That said some of the computer tubes and TV tubes were meant to handle 600V peaks (or even higher) so they might fair well. The amp features switchable heaters on the board for 6.3V so either pin4 and 5 or pin4+5 and 9 for the 12V units. It also has switchable CCS so the current can be lowered with a jumper for tubes that can handle less power. Right now the list of tubes this one can use is : ECC99, 12BH7, 6N6pi, 6CG7/6FQ7, E182CC, 6840, 6350 and 5687. Should be more out there...

Thanks everyone!! Spent the day working on a new version of the KGST amp.

I'm going to go through my archives to see if there is anything to add to the list.

It's crazy so I like it.

That would work but you have to leave enough of the 10M90 hidden as the tab is live. Personally I'd just place the 10M90 on an external sink of some sort.

Simply using the chassis won't be enough. Add some thick aluminum plates as heatspeaders and then some heatsinks will work. Something inline with this: You can use internal heatsinks if there is enough airflow for them to function properly. There are no chassis like this so you need to fabricate everything.

It's not a sunrise as it never went down in the first place. Here is the odd bit, we are so used to this that our natural clocks aren't knocked off balance. Since we have the reverse effect in December we can't rely on daylight as some barometer of what time it is. This comes with being raised here but my friend from CT is still not used to this after 6 years.

I really doubt that the phones arrived like that but it could be a Monday unit or the assembler had just done 100 Sigma's (as the driver there is facing this way). For glue you can use good double sided carpet tape, the type that doesn't leave any residue. Tesa makes some nice stuff plus a bunch of other manufacturers.

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.