lots of errors in that schematic

http://gilmore.chem.northwestern.edu/kgsshvproductiondual.pdf

the dual transistors are in parallel. you use one or the other, not both
one is ebc the other is ecb hence the 4 pads

 

updated schematic still have to add the mosfet drive option

 

http://gilmore.chem.northwestern.edu/kgsshvproductiondualmot.pdf

 

next version of the off board

 

http://gilmore.chem.northwestern.edu/kgsshvampv15mini.jpg

Edited May 10, 201412 yr by kevin gilmore

The PCB version that I was looking at only had half the transistors labeled, so I assumed that they were the same in each pair. Good to know not to build it. I removed the schematic so that no one else does either. Thanks for the updated version.

we generally just put up a first picture of a new board. The production version has lots of small errors fixed.

up to the 5th version of the off board version with servo and dual current sources already. takes too much

time to update the picture every rev.

Kevin - In the latest revision, pin 3 of the OP27 is shown as connecting to the 0.1uF cap that previously was to ground. Is this still to ground ? Are you essentially just grounding pin 3 from the previous version? Thanks.

that side of the cap is still ground. no way to do a thermal for pin 3 due to nearby wires

I think the device labels on the lower A970/MPSW56 pair are reversed on the ampv15 board. They don't agree with the previous version. The upper pair look OK.

Yup, that's correct and it has been fixed. 

latest version

 

http://gilmore.chem.northwestern.edu/kgsshvampv16mini.jpg

One question.  I own a T1 and SRM-1 but I would like to check sth new.  For a first build. Is it better to build an on-board or off-board version?  Visually I like an off-board better.   Mini is great but as I am reading here  there have been too many problems so far.

No problems with the mini but for a first build, it will bite you and bite hard.  I'd do an onboard as then it can be tested safely and then assembled. 

Thank you Spitzer. I will search for on-board version boards then. If you or anybody else know the source or have the latest boards for sale please let me know. 

I'm out of boards but we can supply you with the gerber files needed to have the boards made. 

Hot off the presses, KSSHV mini THD measurements.  I asked Justin to measure my first prototype of the mini and here are the results:

 

 

kgsshv thd results @ 100Vrms and 30khz low pass filter enabled:

100hz - .0087%
1khz - .0084%
10khz - .0107%
15khz - .0222%
20khz - .0259%

20khz w/ 30khz low pass filter disabled - .0719

both channels are very close to the same thd

 

Compared to the BHSE measured using the same setup:

 

 

100hz - .003%

1khz - .0032%

10khz - .0078%

15khz - .0049%

20khz - .0051%

20khz - .015% (with 30khz low pass filter disabled)

 

This is very impressive indeed and I'm sure the second version is a bit better as I switched to 2SC4686A's for that one for lower Cob. 

Impressive measurements indeed esp the bhse, haven't seen those figures before so something new.

I posted it on head-fi and was told the numbers were too high

Sent from my iPhone using Tapatalk

high compared to what?

 

stax amps are rated at .01% at 1khz.

 

eddie current electra is between 1 and 2 %

same thing with the wes

 

if you really want .000000001% thd, you have to buy a LL

That the thd increased at higher freq

Sent from my iPhone using Tapatalk

How about a measurement for T2 KG?  I'm curious to find out.  Many thanks in advance!

the only amplifiers I know of that are absolutely flat THD vs frequency

are CFA's.  No way to build an electrostatic amplifier that way.

 

my equipment is much older than justins gear, and the T2 when

measured the same way that stax measures it comes out better

than .01% No way am I shipping my T2 to Justin to have him

measure it with his pile of late model Tektronix stuff.

 

people over there lacking a clue do not understand that an electrostatic

amp with a minimum gain of 54 db (eddie current) and a typical gain

of 56 or 60db is going to have to perform differently than an amp with

a gain of 6db.

Edited May 18, 201412 yr by kevin gilmore

Many thanks for resurrecting the T2 KG as well as those who've contributed.  I can't stop smiling every time I listen to it with my SR009.  Oh, the KGSSHV is wonderful as well.

Edited May 18, 201412 yr by purk

I am finished!! Check out my post here: 

I could always send Justin the highly modified LL1 to measure.  It's not like it isn't just gathering dust here but it wouldn't give the right impression as unlike the stock version, it's not a shitstorm of distortion.   I have an Exstata too somewhere though it was a highly modified version.   One amp I'm truly interested in seeing measured is the SRA-12S as it was their first foray into solid state. 

 

The T2 was a crazy project, we haven't done one of those in a while.  I've been gearing up to rebuilding the amp section in mine and reworking the PCB design quite a bit in the process. 

I’ve sometimes wondered what the distortion would be for these amps.  Not that I’m in any way worried; the incredibly detailed and transparent sound says a lot.  But they are very impressive figures.

 

I want to thank Birgir and Kevin for developing the smaller and simpler PS.  Now builders have some very useful options.  This is where I came in 18 months ago and was pondering using a 350v-400v PS.  As it turned out I went for full KGSShv and have had a very interesting year of the Stax.  My final effort is the Cube which is as small as I want to make a full KGSShv.  242 W x260 D x180 H. (9.5” X 10.25” x 7” plus feet).

 

 

Really nice

 

I love the form factor.  It give a very small foot print.  Something I might consider in the future.

 

Congrats!

 

Edit:  Internal pics please.

Edited May 18, 201412 yr by Kerry

These show how it goes in.  It is very tight when it comes to screw up the terminals, am looking into alternatives to make for an easier assembly.

 

I should mention for the eagle eyed that the trial assembly did not use both the final amps.  They are different.

Edited May 18, 201412 yr by headinclouds