Yes, that breadboard is starground as well as a connector for the transformer and the switch. 

So your star ground is the breadboard with terminals on the left?

Thanks. I'm trying to figure out the most elegant way to deal with the ground connection on my in-progress builds, and I like your breadboard setup. How did you connect the star ground terminal to the chassis? Just a wire and a locking nut? Did you use the inside rails on the Modushop case for it, or did you drill a separate hole? (A detailed photo would be much appreciated, too.)

The star ground of the bread board is connected to the chassis through the wires leading to the IEC. The IEC has a ground to chassis connection through its mounting screws. Furthermore the XLRs and also directly connected to the chassis through their mounting screws. The toroid, the IEC, the PSU board and the amp boards have direct connections to the bread board.

Thanks. I'm trying to figure out the most elegant way to deal with the ground connection on my in-progress builds, and I like your breadboard setup. How did you connect the star ground terminal to the chassis? Just a wire and a locking nut? Did you use the inside rails on the Modushop case for it, or did you drill a separate hole? (A detailed photo would be much appreciated, too.)

Edited February 13, 201511 yr by insanity

I see, thanks, that's really helpful! What IEC inlet model is that? I don't think the ones I have been considering have ground-to-chassis connections through the case mounting screws.

Its this one: http://www.mouser.ch/ProductDetail/Schaffner/FN9290-4-06/?qs=%2Fha2pyFadugBZovmQ3il67V%2F2HEIfMEF%2FTt44J7gppo%2FoQvTfCvEHg%3D%3D

Total overkill probably.

Edited February 13, 201511 yr by insanity

In case anyone is interested, it looks like the KGST power supply board is an updated version of the original Blue Hawaii power supply circuit  that is published on the Headwize site, with a 10M90S current source replacing the 2SA1968 transistor and LED current source that drives the zener diodes, and an 8N80C MOSFET pass transistor in place of the IRF transistor.  Someone correct me if I'm wrong.

I think this isindeed  the case, and there's some identification on the silkscreen

Well, there are not a lot of parts on the PS circuit board, so there are only a limited number of ways for them to be connected.

It is a modified version of the BH power supply.  Just look at the files on Kevin's site, the clue is in the file names... 

Ah, thanks spritzer, missed that completely. 

 

On a related topic I have signed up for the KGST group boards, and unless I missed it somewhere I don't see part numbers for the terminal blocks on the amp and PS boards.  Any suggestions that are available at Mouser?

 

And somewhat off topic, what do you think of my revision of the venerable SRX design?

The phoenix contact blocks are nice to work with, 

 

Mouser 651-1729131

 

But the chinese ones on ebay are too cheap to not use.

Thanks, no pants.

http://www.mouser.com/Phoenix-Contact/Connectors/Terminal-Blocks/Fixed-Terminal-Blocks/_/N-7rqd7?P=1z1413e

Also try eBay. A lot cheaper....

Edit: too late. No pants beat me to it.

Edited February 21, 201511 yr by Laowei

The problem with the ebay ones is that they are mostly crap.    I'm moving to use the old Buchanan ones now (TE) as I deplete my stocks of all the other ones.  

 

And somewhat off topic, what do you think of my revision of the venerable SRX design?

 

I'm not too keen to use the 6SN7 at this level even it it is a GTA/B.  I ran my "Stúfur" design with GTB's at 600V in grounded cathode and it wasn't ideal.  That was a cheap "volksamp" attempt so a small compromise wasn't a problem.  That said I did have the SRX pcb design open yesterday so I might build some.  I need to make it about half the size and have the tube sockets face the right way.    I have some oddly shaped boxes which would work for this and not much else.  Well that mini BH design I was kicking about would also work... 

Well, the standing cathode to plate voltage with plus-minus 350 v PS rails is about 335 volts, which is well within the max plate voltage spec of 450V for the A and B versions, and with the output current loads at 7-8 mA the power dissipation is about 2/3 of maximum. Moreover, the A and B versions were widely used in early 50s TVs, so they also have a peak cathode-to-plate voltage spec of 1500 V - that is right out of the RCA tube manual. This compares reasonably well with the 6S4A which has a peak plate voltage spec of 2000 V. When I was debugging and adjusting my prototype I often had 600+ volts on one of the 6SN7GTA plates for several minutes without getting any breakdowns or sparks. That was not deliberate - it's just that if the output tail current source is not within range one plate will sit near the positive PS rail and the other near the negative PS rail. As far as I can tell there was no damage to the tubes with this "abuse", they tested within spec on my tube tester afterwards. 

 

More to the point, with the original SRX using 50k output plate resistors and 7 mA through 6SN7GTA/B output tubes, run at 350V, if you swing the maximum peak-to-peak voltage, all of the tube current is going to drive the plate resistors with nothing left for the headphones.  With a simple 10M90S current source at about 170 kilohms  impedance, about 2 mA out of 7 mA of the tube current is going to drive the current sources, leaving 5 mA for the phones - much better.  With the cascoded current sources at over 150 megohms impedance about .002 mA of the tube current is driving the current sources with nearly the entire 7 mA of tube current still remaining to drive the headphones.  I would maintain that makes a significant difference in how well the 6SN7GTA/B tubes work in the circuit.

 

Anyway, I would be very interested in your impressions, since I have not had a chance to compare its sound with any other amp, and of course a child is always beautiful to its parent.  )

Edited February 26, 201511 yr by JimL

I am curious, has someone measured the distortion of the 6S4A on the KGST?

To all who own a KGST and a KGSSHV. Which one do you like better with the 009? 

I have a clear preference for the KGST that persists even after rebuilding the on board KGSSHV with c4686 instead of 1n100d. I would have expected them to become almost equal, but to my ears the difference is not small. 

 

Can anyone else share their impression on this? I am even thinking about selling the KGSSHV and building a second KGST or just get a BHSE?

I didn't do a a side by side comparison but KGSSHV + 009 is too bright for my tastes. I think the KGST + 009 would also fare better for longer listening sessions.

 

The KGSiC might be an interesting alternative to a KGST if you're fiending to build something else? 

To all who own a KGST and a KGSSHV. Which one do you like better with the 009? 

I have a clear preference for the KGST that persists even after rebuilding the on board KGSSHV with c4686 instead of 1n100d. I would have expected them to become almost equal, but to my ears the difference is not small. 

 

Can anyone else share their impression on this? I am even thinking about selling the KGSSHV and building a second KGST or just get a BHSE?

Perhaps the 009's are not for you. 007 may be more to your liking as some people do

I've finished my amp.

 

 

Looks very nice Jose! What is the knob to the left of the volume knob for? And, how does it sound?

Edited March 3, 201511 yr by Pars

Thanks!

 

The left knob handles the input selector. You can see it on the rear corner. Tomorrow I get better photos.

 

It´s my first electrostatic amp and I can't compare but It ´s infinitely better than my SDR7 obviously. The bass is deep and powerful, without distortion or saturation, it's the most obvious difference. The sound is very nice, rich in details. I´m enjoying my Lambda Pro.

 

Sorry, I can´t dwell much. The English is not my native language

 

Now I´m thinking about a brother... a KGSSHV?

Edited March 3, 201511 yr by jose

El amplificador te salio super bien, Jose.  Felicidades!

 

Saludos,

Sam

Yes. What Sam said