insanity

50V is fine and recommended in the BOM.

Look how beautiful it is Just listening to Beethoven's Waldstein.

134f doesn't seem that much to me, although i agree that there should be some venting. Did you build the 350v or the 400v version?

My KGST is finished, only the frontpanel is missing. I must say I am really impressed. Have not had time yet to do a 1 on 1 with the KGSSHV (IXYS parts), but it sound really really good. I'd say there is something special to it, the KGSSHV doesn't have. May be the secret lies in the tubes? It's my first tube amp. It sounds sooo good, it give me a chill all the time. What do you think about the difference between the KGST and the KGSSHV? My memory tells me that in the KGSSHV the difference between the sa4686 and ixys parts is really minor. Can someone confirm?

Yes that is a very good idea to put it "between" the dual primaries (I know what you mean). My question was also how to calculate the optimal value for it? I happen to have 10ohm thermistors. I this a good fit, or would you recommend another value?

What is the recommended thermistor to serve as an inrush current protection for the KGST and KGSSHV? When I built my KGSSHV I used one that was listed in a BOM, without giving it much thought. When using 230VAC mains, would you put one in series with the primary?

just finished drilling the holes for the two amp boards. I used the printouts as a reference, but to get it really spot on, I put the boards on the stand offs and painted the bottom of the stand off with a liquid color. Then I pressed the board down in the correct position and lifted it straight up. I was at maximum 0.5mm off from the printouts. Color marks punched, drilled and threaded. Perfect fit. No too big holes with washers and nuts! Now I'm waiting to get the m4 stand offs for the psu board. Should have ordered some way earlier... P.S. I was surprised how well I could work with the 3mm aluminum plates of the modushop slim case. For the KGSSHV I used the Pesante series case with the steel plates, which were harder to work with. To drill the 24mm holes on the back panel for the XLRs I used a drill like this one: http://www.amazon.de/STB-MASTERTOOL-Stufenbohrer-HSS-6-30mm/dp/B00ECUZ1N0/ref=sr_1_9?s=diy&ie=UTF8&qid=1414337361&sr=1-9 (no idea what its called in english). Worked surprisingly well. Plus the slim series is IMHO a better construction and sturdier - also a bit more expensive though. A question to people who have mounted the alpha pots directly to 10mm front panels. How do you do it? Do you get a threaded hole for it, when you have the frontpanel made? When I built my KGSSHV I used a stepper instead of a pot and mounted the stepper on a bracket very close to the rear xlrs. I used a extension rod to get to the front. The frontpanel only needed a 6.1mm hole.

This works. Thank you again Kevin.

This works perfectly thank you. Is such a pdf available for the PSU too?

Thanks Kevin Amp board is production rev. 0.41 PSU ist version 1.0 (with the too big holes for m3 studs) Hope you find the PDFs. Since these are the boards from the group buy, I think these files would come in handy for quite a few people.

I am just doing the case work for the KGST. When planning to drill the holes in the bottom plate for the boards, do you guys use a printout of the boards as a model? If yes, how do you print it in the right size? I tried to print the KGST and PSU from the gerber files, but something is not right. The holes don't really fit. May be I don't have the right gerber files from the group buy? Is there any other techique you would recommend to get it as exact as possible?

The file can be found here: http://gilmore.chem.northwestern.edu/boards/ But I think this is not the correct file. There is no SOT223 package on the board.

I am just choosing the case for my kgst. So far I tend to get a modushop slimline 3U case 280mm depth with 10mm front panel (2U is not enough unfortunately). I wonder how much ventilation I need. They offer nice ventilated cover which could also be used as a bottom plate. I was think of just getting a ventilated cover. 1. Do you think the bottom plate should be fully ventilated too? Or would you just drill a few (nice) holes under the tubes? 2. Why isn't anyone using the inner drill bases they offer? Makes the bottom plate look nicer (although one probably never sees it )

Update: When i short the inputs the amp is silent. Must be noise from my test source then (Yulong D100 mk II). Doesn't really compare to the Invicta which is my usual source.

I know what they are for. I still have to add them in the KGSSHV though. A question to running KGST owners: Are you amps completely silent like the KGSSHV or is there a minimal amout of background noise? After some more listing to mine today, which is still uncased and a provisional setup, I noticed that its not dead silent after all. Its not a grounding issue - its not a classical 50hz hum. It's more of a higher pitched sound. Is it normal that there are some unpleasant sounds when turning off the amp with the headphones plugged in? Here is a pic of my test setup:

Thanks for sharing your experiences. Since I have the PCBs from Birgir, I have to wait to mount them until the chassis is ready. When I was looking at the KGST and most recent KGSSHV boards, I asked myself the following question: Since these boards incorporate the 2 100ohm input resistors which are directely in the signal path before amplification, would there be any profit in choosing higher quality resistors than the usual rn55 oder xicons? Of course the signal passes many other resistors on the board as well. But this was just a thought.

I have those... But I didn't want to put the pcb on the jack yet. With the PCB mounted it seems impossible to insert screws. How do you guys do it. Screw the jack into the case and then mount the pcb?

Ok guys, I am an idiot. I messed up the wiring of the stax jack. I switched the bias and one of the output lines... I don't really know how it was possible to get good sound on one side like this. Everything is fixed now, works as it should. I feel so ashamed. Sound seems pretty good so far, but I cannot really comment much on difference to the KGSSHV yet. I will try to do this, once it is cased up and connected to my regular source. This will take some time, since I have not yet decided on a case to get.

Ok guys something weird is going on. I replaced the input stage of the "faulty" channel - no effect. Then I switched the O+ and O- wires running to the stax jack from one board to the other and vice versa. I expected the problem to switch sides. But the problem stays on the same side! WTF? As I said the headphones work perfectly with the KGSSHV. If I interpret this correctly, this leaves me with either a bias problem or a faulty cable to the stax jack. Just to be sure how to correctly set the bias voltage. Measure between GND and Bias Testpoint and turn the 1M pot until = 580V. Measurement after the 4.7M resistor gives me around 400V.

The headphones work fine on my kgsshv. I also switched the source channels to rule out a problem with the source. Tomorrow I will double check every connection and do a comparative measurement of both channels hoping to find a difference.

Bias is set to 580V,

Yes everything adjusts fine.

Today I tried to listen to some music for the first time. One channel is perfectly fine. The other one only transmits low frequencies with distortion and no high frequencies. Without a signal it is dead silent. I changed the tubes, no effect. Where would you start to look for the problem? I guess it must be some device in the 1st or 2nd stage maybe?

Could you elaborate what you mean by cracking?

My KGST is up and running. Got the transformer yesterday from toroidy. As expected it is dead silent. Everything seems to work fine, no explosions. Balance and offset can be zeroed. Haven't had a chance to connect a source and headphones yet. I'll probably do this on the weekend. Uncased pictures will follow on the weekend.