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you really want most of the power in the resistor and not the pot.

that said, i don't think andy/steve have the servo turned on, but the thing is already so stable...

i still have 2sa1968's and 2sc4686's available, i'm keeping the rest of the stuff. also have fqpf8n80c

the circlotron is a must build, but way more complicated.

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My own Carbon, not going anywhere... IMG_6585 IMG_6590 IMG_6592 IMG_6593 IMG_6595 IMG_6596 IMG_6597

So I finished my my KGSSHV Carbon a few weeks ago. Been too busy listening to it, but I thought I would share my effort and measurements. I am lucky enough to have access to some test gear that allowe

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Updated BOM and Mouser projects:

For GR HV Dual - replaced the Fairchild uninsulated 7815/7915 with CJR insulated ones per wokstarr26

For HV Carbon V5 - replaced 182ohm offset pot tail resistor with 100ohm to get to 20mA current per Kevin 

Edited by mwl168
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Dropped the current back down to 15ma on mine (had to put the 182ohm resistor back).  The highs seemed a bit too intense at 20ma, seems better now.  The drop may have impacted the soundstage some, making it more compact.  I am really interested to see what others think/discover.  I may try going back up a little more.

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there was some discussion over there and calculations of the current needed to drive the headphones at full power at 20khz. That number is something like 18ma or so, the T2 is 16ma, a lot of the other amps are much less. at 20ma, the carbon has both a faster rise time and wider frequency response than anything else out there. So for a while it seems bright, then it seems more natural. Definitely a difference.

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You can run either one assuming the PSU and transformer are up for it plus the heatsinks.  Mine are all run at 400V because I don't see the point in going higher.  

Yes, I will say it wasn't an annoying brightness, just something I was not used to hearing.  Maybe I will try again.

With the 009 perhaps....??  ;D   

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I updated the BOM and Mouser project for the Carbon V5 to use Vishay RN60D 174K resistors for the two 175K positions. The correct part to use is Mouser part # 71-RN60D1743F. It's a mil-spec resistor that is actually 1/2W even though it's listed as 1/4W. 

The previously listed Xicon 174K resistors are rated 1/4W  and not sufficient for these positions. Sorry for the oversight.   

  

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i just wanted to share 2 things i noticed during assembly of the GB amp boards.

The Dn2540 and the 100ohms trimmer adjacent to it, are quite a tight fit. I used vishay trimmers and the dn2540 has to be soldered with a slight angle. Maybe the bourns trimmer have slightly different dimensions?

Furthermore, I noticed that the holes of the 1uf 50v cap of the servo are quite tight. This probably doesnt affect caps with this rating. but i had 1uf 250v and the leads are a bit too thick for a nice fit. 

 

I also must mention that the boards are very good quality. I have never soldered on boards the seem to suck in the solder that good. 

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Any particular benefit to using the film QYX1H474KTP over a  standard ceramic .47uf 50v cap? The film ones have some size to them as well.

 

Hi George:

I received my Mouser order today and you are right - the QYX1H474KTP is quite large in size. I am not sure if using film caps in these positions has any benefit over using the MLCC capacitors. I picked film caps because I generally prefer them over ceramic caps. For better fitment, I updated the BOM and Mouser project to use MLCC caps (Mouser part #594-K474K20X7RF5TH5). 

Hope others more knowledge about the circuit can chime in which caps are better for these positions and why.

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Thanks to Kevin, Birgir, Kerry and James....and mwl168 for the GB!!

Mine is running now...very yummy!

I used a 32120 Full aluminum chassis Amplifier Case External Size:320×120×311mm

boards mounted vertical with Antek transformers, Xicon 273 series resistors

I swing the heatsinks out to adjust pots and use a 16" non conductive tool

it came up fine with no problems, adjusted current to 14ma for now, set balance and offset.

not using the servo's yet,

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For the GR LV board (not sure if this applies to the HV as well), I'm not sure why "audio grade" electrolytics were chosen for the 220uf and 4700uf caps (Elna Silmic and Nichicon KS) with 85ºC rating instead of long life higher temp 105ºC caps?

Measuring for the 220uf cap, the board allows up to 10mm diameter with 5mm LS. For the 4700uf cap, up to 25mm diameter with 10mm LS (snap-in, though leaded could probably be used).

Edited by Pars
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I used the following caps on the LV board:

http://www.mouser.ch/ProductDetail/Nichicon/UVZ1H472MRD/?qs=%2fha2pyFaduhJNBfNrn1z57sARJAwCa5EYPGgZi6O34PyKHzMMWJAtA%3d%3d

http://www.mouser.ch/ProductDetail/Nichicon/UHE1V221MPD6/?qs=sGAEpiMZZMtZ1n0r9vR22VnKtxyD4xsRvYMdZpGna94%3d

Which are both rated to 105C, in case you were refering to my boards. 

 

I'm using rn60 1% resistors in almost every place. I am surprised how accurate the GR LV is. They read +15.005V and -15.006V. 

 

As you might have noticed I also had to cut a strip off the ceramic insulator pads on the GRHV PSU because the two adjacent 10m90s wouldn't fit as is.

 

Edited by insanity
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Hi Pars and insanity:

I chose the caps in the GR LV BOM for no particular reason other than personal preference. I always liked the Silmic caps. However, the longer life spec should be a major factor to consider as well. I have added the caps Pars listed in both the Mouser project and BOM as alternatives. 

Size wise, they all fit the board fine. The 220uf Silmic is a bit taller.  

Edited by mwl168
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Double posting here but I had my GoldenReference LV Dual running which is built with board from the Carbon GB. The regulated output is rock steady and even though it shows +/-14.98VDC it's within the range of the LT1021-10 tolerance (0.5%).

 

GR LV Dual.JPG

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A better meter with more digits in the display would give you greater accuracy not only in the number of digits but also in the accuracy of the meter.

 

When I used to calibrate meters I found some multimeters such as "Parameters", whilst not as rugged as a Fluke and not specced a good as a Fluke were usually more accurate than a Fluke. i.e. they were very close to spot-on rather than just somewhere within the tolerance range.

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