KGSSHV Carbon Build Thread

[Kerry]

The noise seemed to be caused by leakage between resistors and possibly to the ground plane, though since I had lifted all resistors (PRP & Xicon) it doesn't seem like it was the ground plane.

I agree that the noise was not an issue having to do with external sources.

Regarding noise measurements on the PS boards, I'm using custom boards so I don't think my results will carry to the GB boards.  Also, unless I screen my room, I would not likely be able to see any differences in performance unless they were fairly large (>10mV).

[sorenb]

9 minutes ago, Kerry said:

The noise seemed to be caused by leakage between resistors and possibly to the ground plane, though since I had lifted all resistors (PRP & Xicon) it doesn't seem like it was the ground plane.

So you are talking about noise you've discovered using your custom boards rather than the GB boards?
Can you elaborate a bit on the reason why you believe that the noise your are measuring is caused by leaking resistors?

[Kerry]

Sorry, the noise being discussed was regarding the T2 batteries, not the PS boards.

The last paragraph of my post was discussing the PS boards.

[sorenb]

1 hour ago, spritzer said:

Those noise issues have nothing to do with external sources but rather a flawed circuit design. 

Can you elaborate a bit on the reason why you believe that the circuit design is flawed? does it include both PSU and AMP board from the Carbon Group Buy?

[GeorgeP]

5 minutes ago, sorenb said:

Can you elaborate a bit on the reason why you believe that the circuit design is flawed? does it include both PSU and AMP board from the Carbon Group Buy?

He's not referring to the carbon.

[kevin gilmore]

for the 100mm heatsinks whats the real maximum distance between the bottom of the board and the top of the sicfet package

[spritzer]

Any engineer will call a circuit flawed it it needs that part and that part alone to function when seemingly identical or even superior parts have issues.  The issue was never the ground plane as the coating on these resistors should easily handle 1kV.  What the Xicon's have compared to something like the CMF60's is that they are slightly inductive. 

Also the T2 is a great circuit?  Who in their right mind would say that?  Many neat ideas for sure but far more what the fuck were they thinking bits thrown in the middle.  Same could also be said about the Blue Hawaii in some ways though. 

[GeorgeP]

There are actually quite a few such references in the T2 thread, won't look for them all, but the following was found fairly quickly:

 

 

[purk]

1 hour ago, spritzer said:

Any engineer will call a circuit flawed it it needs that part and that part alone to function when seemingly identical or even superior parts have issues.  The issue was never the ground plane as the coating on these resistors should easily handle 1kV.  What the Xicon's have compared to something like the CMF60's is that they are slightly inductive. 

Also the T2 is a great circuit?  Who in their right mind would say that?  Many neat ideas for sure but far more what the fuck were they thinking bits thrown in the middle.  Same could also be said about the Blue Hawaii in some ways though. 

How so on the Blue Hawaii?  It is still a golden standard along with the T2 for many years.  To my newbie mind, they are all excellent.

[congo5]

1 hour ago, kevin gilmore said:

for the 100mm heatsinks whats the real maximum distance between the bottom of the board and the top of the sicfet package

I measure 102.68mm from board edge to top of sicfet ceramic pad.

that's with the leads bent at 90, so with a sharper bend....should fit

[luvdunhill]

Any engineer will call a circuit flawed it it needs that part and that part alone to function when seemingly identical or even superior parts have issues. 

Don't forget to blame the new PCB layout as being a potential problem as well. Who knows, maybe all types of resistors worked in the original layout.

[JoaMat]

5 hours ago, spritzer said:

Any engineer will call a circuit flawed it it needs that part and that part alone to function when seemingly identical or even superior parts have issues.  The issue was never the ground plane as the coating on these resistors should easily handle 1kV.  What the Xicon's have compared to something like the CMF60's is that they are slightly inductive. 

Also the T2 is a great circuit?  Who in their right mind would say that?  Many neat ideas for sure but far more what the fuck were they thinking bits thrown in the middle.  Same could also be said about the Blue Hawaii in some ways though. 

Blaha!

[sorenb]

23 hours ago, spritzer said:

This is a place for people to learn ...

 

13 hours ago, spritzer said:

Those noise issues have nothing to do with external sources but rather a flawed circuit design. 

 

10 hours ago, spritzer said:

Any engineer will call a circuit flawed it it needs that part and that part alone to function when seemingly identical or even superior parts have issues.  The issue was never the ground plane as the coating on these resistors should easily handle 1kV.  What the Xicon's have compared to something like the CMF60's is that they are slightly inductive. 

Also the T2 is a great circuit?  Who in their right mind would say that?  Many neat ideas for sure but far more what the fuck were they thinking bits thrown in the middle.  Same could also be said about the Blue Hawaii in some ways though. 

in terms of "learning" something here, can you be more specific to what might be wrong in your view?

in rgrds to the Blue Hawaii I guess the "what the fuck were they thinking bits" must be the found in the third of fourth stage of the Blue Hawaii? what should be different or improved upon in those stages?

[spritzer]

8 hours ago, luvdunhill said:

 

Don't forget to blame the new PCB layout as being a potential problem as well. Who knows, maybe all types of resistors worked in the original layout.

No that info came straight from Stax.  I didn't take it too seriously though as it was so silly. 

Not going into a detailed circuit analysis of the T2 here but they basically took a circuit they had (SRX) and threw a bunch of parts at it to make it just about work.  The BH was based on what Kevin knew about the T2 circuit so he came very close with a lot fewer parts.  It can still be done with a lot fewer parts still and give better performance. 

Edited December 6, 2015 by spritzer

[sorenb]

41 minutes ago, spritzer said:

  It can still be done with a lot fewer parts still and give better performance. 

The BH or T2?

[kevin gilmore]

http://gilmore.chem.northwestern.edu/kgsshvcarbonv6.pdf

top blue line is where the ceramics end up and is 98mm from the bottom of the board. If you mount the sicfets at the lower hole.

2nd blue line is optional cut point

the sicfets would be bent .7 inches from the center of the hole which should be doable.

seems to fit, but just barely.

Edited December 6, 2015 by kevin gilmore

[mwl168]

Hi Kevin;

One suggestion, maybe changing the tail resistor of the offset trim pot from 182R to 120R or 100R while you are at it? On my build with the under-size heatsinks, 100R allows me to go to 20mA output current but can not go below 17mA. I believe Steve has similar experience. I am guessing the 120R will provide a broader range of adjustment but cannot confirm till I receive the larger heatsinks I ordered. 

Thanks! 

[spritzer]

You can go lower but we want the offset adjustment to be mostly done in the resistor for temp and drift.  The 182R comes from my boards which naturally have a different CCS. 

[mwl168]

Thanks Birgir! Good point. i do remember that Kevin has also stated somewhere the we want most of the voltage drop to be on the resistor and not on the trim.

When I can comfortably adjust the output current to 20mA with the heatsinks I am expecting, I'll see where the trim pot value ends up and report back with a suggested resistor value.

[kevin gilmore]

kgsshvcarbonv6.zip

kgsshvpssicfetsinglenewleftfats.zip

kgsshvpssicfetsinglenewrightfats.zip

all posted, all are 98mm bottom of board to top of ceramics

resistor changed to 120 ohms.

[gepardcv]

Looks terrific. Thanks!

[mwl168]

I have my Carbon running at 20mA output with the larger heatsinks (10" x 5" x 1.3") I received yesterday. The offset trim pots on both channel are at around 53ohm with 100 ohm tail resistors. So I think 120R tail resistor would work well and allow broader output current adjustment range. I have updated the BOM on the first post accordingly.

With the larger heatsinks, the case temperature of the SiC MOSFET is around 58 - 59 Celsius (around 140 F). The heatsinks are quite worm but not hot to the touch (my infrared thermometer gun does not work with the extruded aluminum heatsink).  

 

Edited December 11, 2015 by mwl168

[GeorgeP]

Did you find that you needed the servo?

[mwl168]

29 minutes ago, GeorgeP said:

Did you find that you needed the servo?

No, I have not needed the servo and, although I have populated the parts for both servos, I have not engaged either one yet. The amp is very stable without the servo. In my experience it's more stable than my KGSSHV which uses the IXTP CCS. 

[kingofsnake]

Happy Holidays everyone..

  Happy to report i have my CARBON up and running for some 6 hours now. I have set the current output to 17ma approx. I attached some digital thermometers to the Hottest part of the 2 heatsinks and monitored the temperature. 35 deg/c  +/- 1 seems to be what they have settled at over the last couple of hours. I zeroed balance/offset to practically zero, the offset drifts a volt or two but much lower than any previous KGSSHV BUILDS. I have found that having 2 headphone outputs makes balance/offset adjustments easier. This amp drives my sr507/009's easily with plenty of range left on the volume control. Speaking of which i was thinking of a relay based volume control such as this http://diyclub.biz/catalog/product_info.php?cPath=1_248_85&products_id=410 does anyone have any experience with these? any advice on alternatives would be appreciated (i would rather something pre-assembled).

  I won't go into what it sounds like (i will leave that to those more capable than myself at explaining such things) But i will say i have put my other amps in the closet for now! this thing just sounds superb.

  As always many many thanks to KG and all those that make these projects possible. Any questions you have i shall do my best to answer them.

 Usual rules apply......If no Pictures.........Then it didn't happen!!   So here you go.

By the way i think i over-did it with the Heatsinks in the psu and could well have gotten away with a single heatsink for the HV +/-.