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KGSSHV Carbon Build Thread


mwl168
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5 hours ago, JoaMat said:

Take look at the schematic. The offset servo can’t be disabled!

I cannot speak to the different versions of Carbon boards and I don't Know which version Sebtdi is using. But for the V5 boards I use there is a jumper that is used to engage and disengage the servo. 

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3 hours ago, mwl168 said:

I cannot speak to the different versions of Carbon boards and I don't Know which version Sebtdi is using. But for the V5 boards I use there is a jumper that is used to engage and disengage the servo. 

this is the version with the servo:

 

https://drive.google.com/file/d/1OPSk_-CRb8OQhS72KpvRyTO07FO70LfT/view?usp=drivesdk

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9 hours ago, Sebtdi said:

your dn2540 looks to be in backwards compared to the silkscreen.... the hashed section on the silkscreen indicates the metal tab... 

perhaps this could be because your silkscreen is wrong or maybe the builder has modified the pcb??

have you checked which pin is connected to what compared to the schematic? and looked at the dn2540 data sheet to confirm the orientation?

 

Edited by jamesmking
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Hello all,

Carbon finally done, tested and buttoned-up - sounds great and very quiet. This was indeed a fun & satisfying project.  I would like to specially thank the following members for all their generous assistance with this challenging build (my first high voltage electrostatic amplifier) Kerry, sweetleaf, mwl168, jamesmking and JoaMat

never worked with SMD's before and needed A LOT of help to debug & trouble shoot issues with the GRHV/LV power supplies, and could not have gone that far without tapping from your guys invaluable experience and know-how. There is only so much one can find inside the forums without getting lost. Thank you for all your patience with my million newbie questions and guiding me in the right direction. I learned a lot from this project and built some additional confidence for the next one.

https://drive.google.com/file/d/1FkZ7RoqedCKawiJt-7tgDJJX6AZyXC9Q/view?usp=sharing

https://drive.google.com/file/d/18HvzLtLvBteYe1kmUapJWf5N8k0qjX_m/view?usp=sharing

https://drive.google.com/file/d/1BstEhS5A36FX8IedeIkk08jyVrDj30ld/view?usp=sharing

https://drive.google.com/file/d/1iJm0reOXiFpjoqV2hYRZgmjf5-uaMpIn/view?usp=sharing

Please let me know if there are a few tweaks that I can do to improve the layout, tried my best to keep it compact in a 2U chassis while separating the power supplies, wiring from the signal to lower noise, etc.. I welcome criticism, every experience is a lessons-learned.

 

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24 minutes ago, johnwmclean said:

Very nice build, any reason you couldn’t have used one custom transformer?

Thank you! 

That's a good point - I really like Antek products and they don't have any 350V with 15V secondaries. Perhaps a custom-made one - did not bothered to look elsewhere.

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On 3/31/2021 at 10:24 PM, JoaMat said:

Here is a version with FJPF2145 in stead of 2SC4686 and 01N100D replacing 2SA1968. The file name is xxx_Mouser to indicate components are available at Mouser.

1928105430_CarbonBJTMouser.thumb.JPG.f92bf5297fb84027fd097c19d63f9c2d.JPG 

Yesterday I completed the left side board and I’m listen to it this very minute. I’m very pleased with the outcome.

Has been in service for a few months now. Sounds alright.

BZ8A0355.thumb.JPG.ebf66f51e35e8f57edf2f55875993883.JPG

BZ8A0358.thumb.JPG.245e7d14a5fc880e3515a196908e0693.JPG

 

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Thanks guys.

Yes, external PSU (T2 PSU with some addons). Maybe one can’t call it a Carbon since output stage is formed by NPN BJT - but else it’s similar.

I think current is like 10mA. 300R emitter resistor and two LEDs in series. With +/-400V the heatsinks are “hand warm” and you can probably double the current.

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As most other DIYers I use Teflon Stax connectors with a small PCB. But on below amplifier I use 3D printed connectors with female golden contacts from Neutrik 3 pole XLR. And they seem to work really well.

IMG_0415.thumb.jpg.16fc52e9c8a43508da3c545ec8e0b581.jpg

On heat sinks are 4 groups of c4686/a1968/c4686.

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5 minutes ago, JoaMat said:

As most other DIYers I use Teflon Stax connectors with a small PCB. But on below amplifier I use 3D printed connectors with female golden contacts from Neutrik 3 pole XLR. And they seem to work really well.

Awesome idea. What material do you use? Not that it would seem to matter, I suppose, as long as it is sufficiently strong. A quick Google suggests PLA has a dielectric strength of >30 kV/mm, and PETG is at >45 kV/mm. That's almost as good as Teflon.

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Thanks for dielectric values of PLA and PETG. Them in picture above are PETG but I’ve also used ABS which also works. I assume you can use PLA as well, but both PETG and ABS melting temperature are a bit higher than for PLA which might be an advantage when soldering wires to contacts.

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9 hours ago, JoaMat said:

Thanks for dielectric values of PLA and PETG. Them in picture above are PETG but I’ve also used ABS which also works. I assume you can use PLA as well, but both PETG and ABS melting temperature are a bit higher than for PLA which might be an advantage when soldering wires to contacts.

Ah, didn't realise you had to solder in situ, that definitely makes PLA difficult. It looked like there was a seam that might represent two parts that 'clamp' the pins in place. But I guess that is probably the subtle layer transition where the bolt head insets end.

I wonder if there any common pin type that might work clamped between two blocks that are screwed together? Could remove heat from the equation, and make jack production extremely accessible if you can use PLA.

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Here are the connectors disassembled.

IMG_0417.thumb.JPG.d2d90b247e35c680959e3e9b16e08b17.JPG

IMG_0419.thumb.JPG.85d66f6b52a001eb198a6fbb5e6d6815.JPG

IMG_0421.thumb.JPG.5b35f1621dd0fc798cf46f677c748609.JPG

Pins are from Neutrik NC3FD-L-B-1. Take a metal saw and make a cut so you can bend up the outer metal housing. Then pins can be removed from inner housing.

I would have prefer Teflon over 3D printed. I haven’t figured out how to mill it out though, but  I managed to 3D print something usable.

Edited by JoaMat
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2 hours ago, JoaMat said:

Here are the connectors disassembled.

I would have prefer Teflon over 3D printed. I haven’t figured out how to mill it out though, but  I managed to 3D print something usable.

Right, so still a clamping design which I imagine makes mounting a lot easier, but you do solder the pins after inserting them. Got it.

 

1 hour ago, mwl168 said:

This is what I used for the socket pins: https://www.ebay.com/itm/143522733990?hash=item216a9f1fa6:g:chUAAOSwga9eN~R4 

They are intended for tube sockets but work very well for Stax sockets too.

Yep, those tulip pins were the ones used in the jacks I got from luvdunhill about 10 years ago. A bitch to solder, but they haven't let me down yet!

 

48 minutes ago, chinsettawong said:

This is my version - 3D printed using ABS filament.

That looks like a direct 3D print of the milled version? Seems to work beautifully with the tulip pins. I imagine you still solder these after assembly?

*

My $0.02 if it were me 3D printing these, I'd flip them upside down and put the 'customer facing' surface on the build plate. It would mean you have to use supports around the overhangs, but you'd get a much cleaner/prettier result on the surface you can see.

I'd also consider using low-warp nylon; if your printer can print ABS and PETG well, chances are it can manage nylon as well, it usually only needs about 250°C on the hotend. The only real difficulty is that you absolutely must keep nylon filament bone dry before and during printing, and use a quality adhesion aid (Magigoo PA is very good on glass and PEI). The real benefit is that nylon will be stronger and more dimensionally stable than both ABS and PETG, and heat resistance should be as good as PETG.

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Hi, guys.

I'm in the process of gathering components for Carbon myself to try and hear what difference it brings to listening experience with my Koss 950s. Problem - C2M1000170D is out of stock at Mouser until the end of the year. So if any of you smart guys have some to sell, please let me know. I REALLY do not want to deal with and risk with the sellers on Ebay etc. Also I could use some PZTA56, DN2540 (TO-220 and TO-92).

Cheers, Kovax 

 

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31 minutes ago, Kovax said:

I'm in the process of gathering components for Carbon myself to try and hear what difference it brings to listening experience with my Koss 950s. Problem - C2M1000170D is out of stock at Mouser until the end of the year. So if any of you smart guys have some to sell, please let me know. I REALLY do not want to deal with and risk with the sellers on Ebay etc. Also I could use some PZTA56, DN2540 (TO-220 and TO-92).

You can use the 1200V Wolfspeed SiC's C3M0350120D instead of the C2M1000170D.
Blueman2 has used the 1200V ROHM SIC's SCT2H12NZGC11 in his GRHV without an issue as well.

PZTA56 is currently still available at RS Components. 

DN2540N5-G is available at Farnell, Digikey, TME. 
The DN2540N3-G is pretty much out of stock currently.

Edited by starcat
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