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.

Edited October 26, 201411 yr by insanity

What I did with my 8mm thick front panel:

>Drilled 9mm diameter thru.

>Counterbored 19mm diameter minimum x 3mm deep (leaving a 5mm length of the 9mm hole). This is for socket clearance to tighten the installed washer and nut.

And modified the Alpha pot by taking a wire cutter to the little piece that sticks up from the mating face. It is there to go in a matching hole in the front panel to stop the pot from rotating. Not really needed if you tighten the nut securely.

I drill a 9mm hole for the Alpha, then I enlarge it 2/3's of the way from the outside with an 18mm drill, essentially carving a hole into the panel for the nut. 

do it right and put in the extra hole for the pot mounting.

 

.393 inch from the center line of the shaft, .125 drill

Agree, do the extra hole for a job done right.

The data sheet also has dimensions.

^ Can't argue with doing it right.

I've been looking over the KGST files in KG's http://gilmore.chem.northwestern.edu/boards/ — what's the intended difference between kgstminiv03.zip and kgstminiv05.zip? The 03 has been updated more recently, so it doesn't seem to be a straightforward version number. (Yes, I've been bit by the KGST bug. KGSSHV, too. Trying to decide which one to go for first.)

 

Also, what does "ST" stand for in "KGST"?

 

Thanks!

ST = "Single Triode"

 

 

//UFN

The 03 and 05 are the same except the 05 is slightly smaller since I needed that. 

Today I have finished the amp. It sounds really great, but I think that's always the case after finishing an audio project. First I have to listen for a couple of days.

I still have a question about the servo.

After running the amp for three hours I adjusted the pots for zero volts, than I turned of the amp, inserted the opamps and closed the headerpins. Is this the correct procedure?

The photos' are not very sharp I am afraid.

I want to thank everybody for helping, especially Birgir, Kevin and Geoff.

Without this forum I wouldn't even considered to build an amp like this.

I really enjoyed the project. Thanks!

The next project will be a balanced DAC. Perhaps the DDDAC 1794 NOS DIY DAC .

Nice build.

For the servo you can leave the opamps in with the jumper open and adjust the amp for 0VDC when it has warmed up.  Then you turn off the amp and put in the jumper. 

What does the servo do exactly? I can't see or hear any difference with or without servo. It still takes some time before the tubes balanced out.

It nulls the DC offset

Okay,that's clear, but how long does it takes? In my case it took an hour before 0 volts were reached. Does this mean the servo isn't working correct?

What do you mean by 0V?  As in it was at 15V and then got down to 0VDC after an hour or that it hit the magical 0V from 0.3V after an hour? 

Without servo the amp had run for three hours. Then adjusted the pots to 0 V and inserted the opamps and closed the headers. When I turned the amp on again I measured in one channel 9 volts and in the other 6 Volts. After an hour I measured 0 Volts in the right channel and 1 V in the left. This is probably normal I guess?

levels are way under the threshold for concern

Without servo the amp had run for three hours. Then adjusted the pots to 0 V and inserted the opamps and closed the headers. When I turned the amp on again I measured in one channel 9 volts and in the other 6 Volts. After an hour I measured 0 Volts in the right channel and 1 V in the left. This is probably normal I guess?

Just curious, are rounding to the nearest volt or are these your actual measurements? Also, is the no constant variation?

I set the multimeter at the highest input (1000V) so there is little variation.

I just expected the servo immediately to respond.

This evening I had more time to listen. It still sounds great.

Perhaps I repeat the measurements and set the meter to a lower input, but first I want to enjoy more music.

The servo takes a while to catch up but if your offset adjustment is right on the limit of the pot then the servo can't make up for that. 

I replaced the 1.5k resistor by an 1.1k one, so there is enough room for adjustments.

In the weekend I have time to walk through the process again and make notes.

It's really a great amp headphone combination. Much more detail compared to my Hifiman-400.

I set the multimeter at the highest input (1000V) so there is little variation.

I just expected the servo immediately to respond.

This evening I had more time to listen. It still sounds great.

Perhaps I repeat the measurements and set the meter to a lower input, but first I want to enjoy more music.

You should (generally) use the lowest setting possible.

It is good practice to start out on the higher voltage settings so you don't blow up meters without protection (maybe better to blow them up, but lets act like its not), but back down to the right (lower) range as you get things dialed in.

Edited October 29, 201411 yr by nikongod

Does anyone have a set of KGST boards for sale?

Try Mangler here or on that other site. Last I heard he had a set for sale for $30 +S/H.