spritzer

That would do it.

Couldn't have said it better. He also thinks the HV is bad with the 009's, he should try that SRM-323S... I also love his response about age. Sure, being younger will often lead to better hearing but experience is the key here. Well that and not being an idiot.

There are 4 zeners for the bias supply, 3*150V and one 130V. That would work but I highly recommend doing a proto run on any untested pcb.

So they want people to use two amps with non stepped volume controls? Wow... that is pretty much priceless. Wait no it isn't, it would cost 3k€...

Just so you know, there are no good offboard versions available. The ones I use in my tiny amp require some care or the amp will blow up (i.e. everything was sacrificed for space or rather lack there of) and the new slightly larger units aren't ready. Too busy building to work on them.

Indeed!! I just looked up this amp and I love how it is supposed to be balanced but there is nothing balanced anywhere. Well unless that 3 pin XLR balanced output is the new fancy version of balanced... with shared ground.

I take it that this is the new king of the fucktards? The amps are clearly to blame here when the headphones have a rather enthusiastic top end. Better stick it on the 727 with very little HF presence and a sound warm enough to shame most SET's. Sure... sounds like a plan. I do wonder if the GES is part of this? Does mean we have to make our own 009 design, cobble something together that barely works and claim it has great synergy....

I really liked the last one...

The caps were shot so replacing them helped. Didn't cure the ever present hum though...

The stock amp didn't have zero offset either. I would have to dig through my email archive for the exact figures but it got a lot better once I redid the PSU

Not much of use there for us. The voltage divider is fixed so drive it off a regulated PSU for a regulated normal bias.

That would qualify as massive

The Antek units I've tried have all been excellent. Something like that 400VA unit is gigantic though...

So a couple of things. First, see this: Looks just like all the KGSSHV's I've built but this one is different. Aside from the 2SK170 input fets it's all in current production. It runs at +/-400V but with just over 8mA of current and uses Fairchild FJPF2145 output devices. Sounds pretty much indistinguishable from a +/-500V version I built as well that is pretty much identical save for the output devices and voltage. Now a couple of neat points about doing the amp this way, first of all the parts are all easy to source and secondly, so are the transformers. Edcor has a nice dual 335V winding unit in their catalog so add a small 30VCT/25VA unit and you are set. No need for anything custom and the PSU mods are dead simple. Just change the zener string and the divider and bypass the voltage divider that feeds the bias supply. The second point is that I've finally given up on thePMBFJ620 fet. Nothing wrong with it except it is just so bloody tiny that it's all but impossible to solder. They will be removed from future versions of the boards and might be replaced with the SMD LSK389.

You'd have to be quick as the chassis for those two amps are already on their way to me. All the boards are ready and have been for months so it's just a matter of doing the chassis stuff. I have so many half finished projects like this that need to be finalized. Way too bloody many...

I have enough parts to build two more KGSS units so they are on my todo list.

Happy Birthday!!

Yup, too busy building amps to work on it though.

All of these BJT's have the same pinout. Yes on the new part but I'll never sell any of my 2SA1968's.

Yeah that and I have a huge pile of 2sa1968's and they are fully insulated which makes my life easier. One thing I missed, the zener string should be 230V as that is the max normal bias voltage. A KGSSHV plus a higher normal bias voltage is not a good mix. It's ARC time!!!

It would make sense to make sure this project doesn't go the way of the Dynahi and be killed by parts being discontinued. It should also be noted that this is the part intended to be used in the KGSSHV all along. The 4686A was just easier to source... No need for that. The audio slush fund covers this...

The current board just about fits a Modushop Pesante Dissipante chassis...

So a question for the group. As we all know high voltage BJT's that can take the full force of the KGSSHV are going away quite quickly. None are currently being made and I quite frankly don't see them making a comeback, certainly not as TO220 devices. There is a new mosfet on the horizon but it's a poor substitute for the real thing. With this in mind I used the mafia network to try and source some NOS and I've hit paydirt. Now 2SC4686A's are all but gone but I've been offered another part which was clearly meant to be used in the same role, all specs identical plus some (like the output capacitance) are even better and it's fully isolated package too. These are also guaranteed genuine and made in Japan. Now the catch is that I have to buy a lot of them, thousands, and the end price is unknown though I hope it comes between 2-3$ when they would reach my hands. The 4686A is currently at 4$ from Bdent and supply in Japan is all but run out. I would naturally sell off my stash as needed to anybody building an HV so this would be enough for a few hundred new amps. So does this make sense to anybody? I see no problem with that.

First off, never use a screwdriver to adjust the pots, that's what trimpot adjusters are for. Non conductive too... As for the pots: New version has the balance moved so the terminal block doesn't obstruct it.

The PSU isn't current limited so it will easily fry the amp given the chance.