[robertopisa]

Hello Morten,

I would like to try to use 3 chassis for the LDR pre:

- PSU power
- left balanced channel (slave)
- right balanced channel (master)

Q1: Should I have to ground also the chassis for the left and balanced channels?

Also, I would like to experiment using a shielded CAT5 cable to connect the T-R-SS-IR pins as you wrote in the instructions: the reason is that I want each channel chassis as close as possible to the corresponding active speaker, so this cable could be 2m long.

Q2: Should I connect the shield of the CAT5 cable to the start ground?

Please find below a scheme for ground and power connections. I am aware that you are very busy now...

Q3: When you have time, can you please check that the connection scheme below is ok for balanced connections?

Big thanks
-R



Larger resolution:

[tortugaranger]

Most impressive graphics Roberto! Outstanding! In fact, I may "steal" your graphic and use it in our documentation! I look forward to your project pics when you're done .

Q1: Should I have to ground also the chassis for the left and balanced channels?

You certainly don't have to. There are no AC mains entering either the master or slave enclosure. Just 12 VDC/ground. The audio signals are pass through. Grounding to chassis is optional in my view. Were it my project, I wouldn't. You may find others with strongly held contrarian views.

Also, I would like to experiment using a shielded CAT5 cable to connect the T-R-SS-IR pins as you wrote in the instructions: the reason is that I want each channel chassis as close as possible to the corresponding active speaker, so this cable could be 2m long.

Since these signals are relatively low speed digital/serial data, CAT5 should be more than adequate.

Q2: Should I connect the shield of the CAT5 cable to the start ground?

Please find below a scheme for ground and power connections. I am aware that you are very busy now...

I would think that grounding the shield of the CAT5 cable is optional given the relative short distance and relative low speed of the serial data stream. If this cable is running along side power mains or otherwise noisy environment then perhaps.

In reviewing the overall wiring I see only one thing that I'd clarify or change. Your PS12.5 has dual 12 VDC outputs. The schematic implies a single 12 VDC feed going to both boards. You should power each board with it's own 12 VDC supply channel. Those 12 VDC channels are positions 1 and 2 on the J5 power/ground screw terminal.

[Speedskater]

One small nit. The AC power Safety Ground/Protective Earth wire should connect to the chassis at it's entrance. The the PS card primary should connect to the chassis at that same point.

[tortugaranger]

One small nit. The AC power Safety Ground/Protective Earth wire should connect to the chassis at it's entrance. The the PS card primary should connect to the chassis at that same point.

Correct. This applies to the PS enclosure when AC mains do come into the enclosure.

[robertopisa]

Thanks! This is the updated picture with with your comments (I will send the files to Morten). Feel free to use. It is useful for me as I want to avoid mistakes.

I am not sure 100% to have correctly implemented your comments below on connecting the ground (G) to the chassis and the PS card primary.

One small nit. The AC power Safety Ground/Protective Earth wire should connect to the chassis at it's entrance. The the PS card primary should connect to the chassis at that same point.

Correct. This applies to the PS enclosure when AC mains do come into the enclosure.

Cheers
-R

[robertopisa]

Hi-rez picture

[robertopisa]

up... is the ground G correctly connected in the updated picture?
Thanks
-R

[tortugaranger]

up... is the ground G correctly connected in the updated picture?
Thanks
-R

The only possible tweak to this I can think of would be to NOT daisy chain the VAC-G(earth) to the PSU Chassis before connecting it to the PS12.5 but instead go direct to the PS12.5 and then have a separate star ground arm from the PS12.5 to the PSU Chassis. I doubt it will be a problem if left as is but the ideal rule in star grounding is nothing gets daisy-chained and instead everything gets its own direct path to the single common star ground point. You could argue which makes for the better star ground point, the PS12.5 or the PSU Chassis. The PS12.5 does have a solid continuous copper ground plane to which all the ground terminals and ground solder pads are tied so it should work fine as a convenient star ground point.

- Morten

[robertopisa]

Hope this figure is better (in the first picture I had a separate arm but it seemed incorrect). Which value of fuse (if any) do you suggest for PS12.5?

Thanks
-R

[Speedskater]

The nits are now getting extremely small, but I like the connection is reply #5 over the one in reply #8.

Note: I don't have a copy of the PSU schematic/ printed circuit board layout, so I'm doing a certain amount of guessing.

[robertopisa]

I copied the initial branch of G from my DAC. The other option is that of first posting in this 3D, where the PSU12.5 acts as star ground, and there is an arm from there to the chassis (in gray) but you were not convinced of that (see picture below). I do not see other options...

Thanks
-R

The nits are now getting extremely small, but I like the connection is reply #5 over the one in reply #8.

Note: I don't have a copy of the PSU schematic/ printed circuit board layout, so I'm doing a certain amount of guessing.

[tortugaranger]

I copied the initial branch of G from my DAC. The other option is that of first posting in this 3D, where the PSU12.5 acts as star ground, and there is an arm from there to the chassis (in gray) but you were not convinced of that (see picture below). I do not see other options...

Perfect!

[Speedskater]

From best to worst:
Reply #4 & #5
Reply  #8
gap
Reply #10 - unsafe -does not meet safety codes
gap
1st post - unsafe -does not meet safety codes

[tortugaranger]

Speedskater's comment prompted me to look back on all the variations. Keeping mind that we're really picking at nits here, the pic in post #6 is arguably the best insofar as earth being grounded to the chassis immediately upon entry. Considered good practice. However, to be consistent with this guidance you'd then also want to make that connection point the center of the star ground. Connecting earth to the PS12.5 board first as per the most recent pic may violate the "earth-to-chassis-first" guidance but in my view represents a better overall approach having the PS ground plane be star grounding point. Either way will work fine. Nit pic nit pic nit pic. 

[robertopisa]

I currently have a plastic chassis for testing
-R