KGSSHV Carbon Build Thread

[Pars]

You can also get Panasonic FM or FR with the right footprint as well

[mwl168]

Thanks Insanity, Birgir and Pars for your help. I took a close measure and I believe Birgir is correct that the lead spacing for the 100uf/25V caps is indeed 2.5 mm.

I changed the Mouser project and BOM to use Panasonic Low ESR caps with 2.5mm lead spacing and 5000 hours rating.

hope this is the last time I am making correction to this part If anyone has stuffed the board please chime in and verify. 

[spritzer]

I think Kevin lifted my LV supply directly for those boards so it should be a 5mm cap with a 2.5mm pitch. 

[mwl168]

Thanks Birgir. 

I measured the footprint of the 100uf/25V caps on the GR HV Dual board and it can accomodate up to about 7.5mm diameter caps. So either should work. The one I included in my Mouser project and BOM is 6.3mm. 

[insanity]

I am planning how to arrange the various boards in a 3U dissipante chassis from modushop (see picture below, white paper = toroid). 

Are there any suggestions on better arrangements of the boards? IEC and XLRs would enter the chassis over the toroid. 

I was thinking of various other configuraitons such as moving the toroid and the HV PSU boards to the front, the LV boards to the middle and the RK50 all the way back. Like this the pot and the amp sections would be on the rear of the chassis. 

Any ideas of what the best configuration is?

BTW: I am planing to use the chassis bottom as a heatsink for the GR LV supply. I think this should be sufficient, right?

Also thx to xianghao for providing me a RK50 pcb. 

Edited September 23, 2015 by insanity

[kevin gilmore]

that is exactly what I had in mind. except for the more basic units, no GR supply, and the rk50 replaced with a rk25 and its associated board.

plenty of room for the transformer, xlr connectors and iec connector.

the boards are 50th short on the width, so all the heatsink holes can be lined up end to end on .5 inch spacing.

transistors on the bottom for the GR supplies, no problem, hanging in the air with the smallest of heatsinks also works.

board layout for the rk50 board in the usual place.

[GeorgeP]

I am clearly clueless on this, but why the GR boards?

 

[nopants]

lower noise than the normal 7x15

[insanity]

I am clearly clueless on this, but why the GR boards?

 

Since sorenb reported that there might be a difference in sound when using amb's psu for the LV Section, I thought I would just try the GR LV instead of the 7815.

I won't be able to tell the difference, because I am not planing to populate the 7815 unless the GRLV blows up or something.

Edited September 24, 2015 by insanity

[mwl168]

... IEC and XLRs would enter the chassis over the toroid...

I

Would it be better to keep the XLR and the signal wires as far away from the toroid as possible?

Edited September 26, 2015 by mwl168

[spritzer]

Yes. 

[wink]

You could always put in a mu-metal shield over the transformer.

[insanity]

Would it be better to keep the XLR and the signal wires as far away from the toroid as possible?

What do you think about a configuration with the toroid and the PSU boards right at the front panel and the pot, and amp boards in the back of the amp?

[spritzer]

That has its own issues due to the proximity to the output socket and its wiring.  Much harder to shield that with all the extra capacitance the shield would generate. 

It should be clear now just how much engineering went into the KGSSHV mini... 

[johnwmclean]

insanity since your using a 3U case you could potentially mount (and heatsink) the GRLV boards above the amp boards, this would clear up the whole centre section for the transformer and attenuator and neaten up wiring.

 

 

[insanity]

@ johnwmclean 

I think thats a interesting idea. I will need to check if the lv boards fit nicely somewhere above the other boards, when I have all the boards populated. Especially because of the capacitor height.

@spritzer

Therefore having the transformer as far away from inputs and outputs is necessary? I thought the input wiring was much more prone to picking up noise?

 

I therefore conclude that maybe the better option is the do the layout as pictured above, but with the xlrs on the side of the chassis instead of the center (above the psu boards, there should be enough space). The IEC can be in the middle. I could run the input wiring along the side of the chassis (under the cover, maybe in shielded cables?) and move the RK50 to the front. Like this the input wiring are as far away from the toroid as possible (btw, I will get a custom toroid with shielding). The output wiring would be short and wouldn't need to pass over the toroid. 

Does anyone know, if mouser has something like this? 

Edited September 27, 2015 by insanity

[Pars]

The input wiring is more susceptible to noise than the output wiring as the signal levels are lower. Having the RK50 at the rear keeps the input wiring shorter, so theoretically should be better.

Mouser does have cable hold downs like you pictured. http://www.mouser.com/Search/Refine.aspx?Keyword=644-CCH12-S10-M

[JimL]

For my SRX Plus build, the raw PS is up front, the PS regulator in the middle and the attenuator and amp boards are at the back, with the output wiring lightly twisted going to the output sockets.  The length of wire does add a few pf capacitance to the output load but it shouldn't be a major problem.  My amp measures 3-5 mV broad band noise at the outputs so there's not a lot of PS noise getting into the outputs.  Of course, the PS and all my boards are mounted vertically so the output wiring is just skirting the edge of them, which may make a difference.

Edited September 27, 2015 by JimL

[insanity]

The input wiring is more susceptible to noise than the output wiring as the signal levels are lower. Having the RK50 at the rear keeps the input wiring shorter, so theoretically should be better.

Mouser does have cable hold downs like you pictured. http://www.mouser.com/Search/Refine.aspx?Keyword=644-CCH12-S10-M

Thx Pars. Will add these in the right size to my BOM. 

For the case layout I guess I will just try one version, if it works, fine - if not, try another. 

I also thought about mounting the amp boards vertically, but like that, adjusting the trimpots will be a pain, with everything put together and I would like to avoid that. 

 

Anyway I am very interested how others want to build their carbons. 

[wink]

I also thought about mounting the amp boards vertically, but like that, adjusting the trimpots will be a pain, with everything put together and I would like to avoid that. 

 

You would need to get a suffix X instead of W, or a Suffix Z instead of Y

i.e. 326X substituting for 326W

 

https://www.bourns.com/pdfs/3296.pdf

[insanity]

Take a look at the orientation of the balance pot. It doesn't works with either suffix.

[UFN]

Would you not mount the amplifier PCB with the transistors at the bottom of the heatsink? In that case, the balance pot is at the top and the standard straight pot should be OK to adjust even after the board is mounted?

 

//UFN

[spritzer]

Mine are built with the boards attached directly to the sinks and I adjust them from the top.  The boards you are using are different from mine though and I'm not sure what version was used on the groupbuy...

[wink]

On the BOM Edit 9/18 on line 19, the cap 80-C320C104J5R is shown as 0.1uF 50V

On the PCB it is 1Uf 50V

[GeorgeP]

On the BOM Edit 9/18 on line 19, the cap 80-C320C104J5R is shown as 0.1uF 50V

On the PCB it is 1Uf 50V

do you have the spacing handy?