i'm on a roll... the kgsshv

[Pars]

Side note, but are r cores not as good as toroids for this application?

Ran across a nice posting on transformer types and their advantages/disadvantages, and couldn't remember where I had seen it. A bit of searching found it, by Charles Hansen (Ayre):

http://www.audioasylum.com/cgi/vt.mpl?f=amp&m=169363

[spritzer]

Side note, but are r cores not as good as toroids for this application?

With a PSU this well designed the type of transformer isn't a big deal. Not that it is a big deal with lesser PSU's either...

[Horio]

Here are a few more photos of my chassis work.

Unfortunately the Hifi2000 Dissipante cases have two rows of vent slots right where the power supply mounts want to be located. To get around this I created a mounting plate. The power supply mounts to the plate, and then the plate mounts to the bottom chassis panel. A little bit of a strange solution, but its quite sturdy and seems to have worked well.

[Pars]

^ Nice solution... you're a lot better at cutting aluminum than I am

[guzziguy]

Agree. Very nice solution.

[Horio]

Would one of you guru's mind posting some basic instructions for bringing up the KGSSHV Amp boards?

I have a healthy PS ready to go, and I'm going to be ready to test my amp boards (off board sinks) this weekend. Just wondering what basic voltages I can check to make sure the amp is working correctly, and if there is a suggested order/method for adjusting the trim pots.

Thanks!

[livewire]

This is what I did.

Disclaimer - I am a DIY stat amp n00b. So take what I say here with the proverbial grain

(or 50 pound sack) of salt. I will not be held responsible if you blow up your amp or headphones.

I know that I am preaching to the choir here, but all the regular B.S. about following safe build

and test procedures without electrocuting yourself apply here too.

1) The psu is to be burned-in for eight hours at 125% of rated power output.

[with a dummy load attached - simulating the load of both amp boards]

After burn-in, ensure that both the high voltage and low voltage +/- rails are outputting the correct voltages and are stable.

2) Short the signal inputs on the amp board to ground, or if already hooked to an attenuator, set it to zero (volume).

No source input signal should be applied at this time.

3) Initially, only hook-up and test/calibrate one amp board at a time.

Important: Ensure that the +/- 15VDC and +/- 450VDC* output voltages from the psu along with ground are connected

to the amp board before powering on. (*make that +/-500VDC in your case)

If any of the LEDs do not light, or are very dim or are blinking upon power-up, something is wrong!

Remove power immediately, then troubleshoot.

4) Assuming that all LEDs are glowing uniformly, perform the following calibration procedure to the amp board(s):

[note: this is copied from KG's HeadWize article on the KGSS. Same stuff applies here.]

"The two pots balance the output voltages to 0V referenced to ground.

Begin the adjustment by putting a voltmeter between + output and - output and setting the first pot for zero volts.

Then put a voltmeter between the + output and ground, and set the second pot for 0V.

After the amplifier warms up for 30 minutes, adjust the pots again.

I adjusted my unit once, and keep checking it every so often.

The output voltages on my unit are less than ±200mV.

Compared to the 580 volt bias, that is close enough to 0V. And that is over a 1-month period."

5) Repeat steps two through four when the unit is cased with both amp boards connected

along with the input and output jacks.

This time, final test & calibrate the output voltages through the Stax jack(s). [without headphones connected]

6) Hookup a source and your headphones and enjoy!

At first, I recommend using a "cheap" set of cans for a while. Sure would hate to fry them 009's!

Edited October 29, 2011 by livewire

[wink]

1) The psu is to be burned-in for eight hours at 125% of rated power output.

[with a dummy load attached - simulating the load of both amp boards]

.

So, what is the resistance and power rating of the resistors you used?

Edited October 29, 2011 by wink

[spritzer]

Fire up the boards and zero out the offset and balance. Not much more to it than that...

[livewire]

Ok, so do what spritzer said.

I was stating what I did.

If you dont care to do step one (burn-in), that's up to you.

With the outputs checked for correct voltages, your psu will prolly be good to go as is.

@ wink - For my 450VDC PSU - 4K ohms @ 50W. One each between each output rail and ground. (2 total)

Vishay p/n: RH0504K000FE02

For the 500VDC PSU, figure 5K ohms @ 50W.

If you do decide to burn-in the PSU, keep in mind this procedure will stress some of the components to their design limits. (and possibly beyond)

This is done to expose any potential weakness in the PSU and ensure a strong unit later on when operating under a normal load.

I recommend bolting the dummy loads to a large chunk of aluminum heastsink to keep them from overheating while running at max load.

Also while under power for eight hours, use a fan blowing air over the whole test set up. (i.e; transformer, psu board and dummy load.

[deepak]

390VA

should be 150VA

450v x .150 amp is 67 watts x 2 is about 140 watts plus 10 watts of low voltage.

Looks like he assumed

450v x .1 amp = 45W x 2 = 90W

+

30V * 10A = 300W

= 390VA

That makes sense. Wrong, but makes sense.

That gives me some confidence in Sumr

[n_maher]

That gives me some confidence in Sumr

easy mistake when the HV was spec'd using current and not VA. I'd put as much blame on the person asking for the quote as I would SumR.

[deepak]

easy mistake when the HV was spec'd using current and not VA. I'd put as much blame on the person asking for the quote as I would SumR.

Yup, no doubt I should have clarified those HV secondaries, he cleared it up after he had the transformer part number.

If people want to start giving me their requests he'll be able to get a better idea of the cost with your exacting specs (mostly addressing overseas users that messaged me).

[Horio]

I mounted the transistors to the Hifi2000 heatsinks yesterday, and I thought I'd post a couple pictures. I had Front Panel Express do the drilling/tapping of the holes. They aren't the cheapest, but did a great job and everything lines up perfectly.

If you are interested, I'd be happy to send you the FPE files (just shoot me a PM).

[kevin gilmore]

wow, so it actually does fit.

you really only need ceramics on the outside 2 transistors.

Edited October 30, 2011 by kevin gilmore

[ujamerstand]

Awesome! Looks like it turned out great!

[livewire]

Nice work!

I hope it ends up working nice.

Looks like you are on your way to having the first KGSSHV outboard. (off-board?)

[HDen]

Beautiful, congratulations!

[spritzer]

wow, so it actually does fit.

Pfftt, ye of little faith...

[TMoney]

And.... how does it sound?

[johnwmclean]

Very nice Greg!

Wnat is the purpose of two outer holes on your FPE hearsink files?

Edited October 30, 2011 by johnwmclean

[wink]

Are those screws holding the transistors PEEK's ?

[Horio]

wow, so it actually does fit.

you really only need ceramics on the outside 2 transistors.

Yea, I knew the 2SC4686's are already isolated, but I decided to put the ceramic pads under all of the parts. They lined up, height wise, better this way with the boards. You need about a 3/8" tall standoff for the way I have it mounted (1/2" is just a bit too tall).

Very nice Greg!

Wnat is the purpose of two outer holes on your FPE hearsink files?

The two outer holes are for holding a cable management clip.

Are those screws holding the transistors PEEK's ?

The screws are PEEK's, 10mm to be exact. With the depth of the holes (6.5mm), the 10mm PEEK screws are a perfect fit with the ceramic isolator pads. I know its a bit overkill, but I wanted to avoid any shorting issues on the IXYS parts. You have to buy 100 of them at a time, so I threw them on the other parts as well.

[wink]

Thanks, Greg.

[cobra_kai]

So I'm getting close to the point of turning this thing on but I have some confusion about my grounding scheme. I am doing a two box on board heat sink build with the amp boards in one chassis and the ps in the other. Obviously in the ps chassis I have ac mains earth ground connected to chassis. I then have an umbilical running between the two chassis carrying both power supply ground and chassis ground, and signal ground also enters the amp chassis. What is the best way to tie these grounds together for safety and avoiding hum? I was thinking I would tie the amp chassis ground to the power supply chassis ground (and thus earth ground) and then connect power supply ground to chassis ground through a resistor inside the amplifier chassis. Does this sound like a safe scheme, and also is it then appropriate to keep signal ground isolated from chassis?