PC board for RCA/XLR SE<->balanced switching?

[Pars 1,597]

Has any one of you done something like this, accommodating a pair of RCAs and a pair of XLRs, with the appropriate switching for these? I know I'll get told to just use the Neutrik or whatever RCA->XLR adapters for this, but I was thinking about doing up a PCB with a pair of something like the Neutrik NC3MAV/FAV and a pair of RCAs.

Has anyone ever used the vertical Vampire RCAs (pcb2f/s)? They don't list any dimensions or PCB layout for these, but just wondering height-wise if these could work well?

I had thought I would probably use relay switching instead of a mechanical switch, as the 4PDT are a PITA to wire up, but I suppose just going into a board with connectorization could make things more palatable.

Thanks for your thoughts, or if you have seen anything like this around.

[n_maher 11,583]

I'm pretty sure that Justin used those Vampire RACs on multiple products.  There's a chance that I have a pair downstairs and if so, I can send them your way for prototyping. I used them on multiple projects (KGSS, Exstata, etc.).

 

[Pars 1,597]

Bought a pair of the Vampire RCAs (ebay) and measured them. I've attached an Eagle library with these in them as well as a board layout using these and Neutrik jacks and NKK switch. I haven't verified any of the board <-> panel spacings yet, but they seem reasonable, with some soldering slop.

Change the file extensions from zip to lbr for the library file.

con-audio.zip

Edited January 5 by Pars

[luvdunhill 3,266]

Are you not worried about the fact that the grounds aren’t switched? I have a recent use-case where it was needed - the two sources were on different electrical circuits.

Regardless, I would consider a jumper for XLR pin 1 to either be connected to the chassis or to GND.

https://www.ranecommercial.com/kb_article.php?article=2107

Edited January 5 by luvdunhill

[Pars 1,597]

From Rane 110, it appears that the "right" way to do it is to tie pin 1 to chassis. The two pins in the lower right corners of the XLRs are also supposed to go to chassis, correct? If so, I could wire these together to a pad to wire to chassis ground.

[luvdunhill 3,266]

2 hours ago, Pars said:

From Rane 110, it appears that the "right" way to do it is to tie pin 1 to chassis. The two pins in the lower right corners of the XLRs are also supposed to go to chassis, correct? If so, I could wire these together to a pad to wire to chassis ground.

I would tie the shell to the chassis and have a jumper for the pin 1 to go either to AGND or Earth.

Does the vertical height of the two parts match up well enough?

[Pars 1,597]

You mean the 3 parts (XLRs, RCAs and switch)? It seems to though I haven't measured or done any sort of mock up. I think there will probably be enough slop possible in assembly to get them to match, but I'll play around with it. The switch is an NKK m2042xxxxx, and the Neutriks are NC3FAV2.

I tied the two chassis gnd connections from the Neutriks together with a pad in the middle, and did the same with the pin 1s. Then put two pads in connected to the board gnd plane. I'll probably add another pad for chassis ground to give the most flexibility.

On my Pass Aleph P, the XLR grounds both go to board ground. Same on Kerry's SS Mini. I haven't had any hum problems whatsoever on my stuff, but everyone has different issues potentially.

Thanks for getting me thinking about this shit though   I also used a drawing of the Cardas GRFA DBL PRT that someone had provided on a diya thread you were participating in to draw up that part in Eagle as well, in case I wanted to go that route.

Edited January 6 by Pars

[willsw 0]

On 1/4/2021 at 10:35 PM, Pars said:

Bought a pair of the Vampire RCAs (ebay) and measured them. I've attached an Eagle library with these in them as well as a board layout using these and Neutrik jacks and NKK switch. I haven't verified any of the board <-> panel spacings yet, but they seem reasonable, with some soldering slop.

Change the file extensions from zip to lbr for the library file.

con-audio.zip 11.31 kB · 7 downloads

 

I've always been confused by Vampire Wire and their lack of online presence. I remember a quaint website but it seems like the domain name no longer works. 

Since I've done a lot of work with this specific RCA, here's the info I have so far, for posterity and reference:

They almost certainly had those RCAs made in Taiwan, either by AEC or First Tech, which have different addresses but could also be associated in some way, given that many of their offerings are identical. I've worked with AEC and have had good experiences with their products. I've attached the drawing for their version of this RCA. Center pin is center conductor, off-center pin is ground, the other pins are purely mechanical and not attached to the others. 

These connectors are usable on the same board as Neutrik vertical-mount XLRs, but you will need to prepare for certain adaptations. I've found a few examples of production components using this connector combination. Kinki Studio has been the most valuable for providing use examples, as they've implemented a few different strategies with both vertical and right-angle versions of these. 

The first approach is to mount the Neutrik XLR with wider slots in the PCB, so that you can slide the mounting pins through and solder the wider part, allowing a reduction in the height of the XLR. I've done this method and used slots that were 0.75mm x 3.4mm. These seem to work fine. You can cut off the original PCB pin from the XLR. Here's an example of this method. In the bottom right of this image, slightly out of focus, you can see the spacing you'll need for the RCAs. A 5mm spacer measured from the black housing seems to work, or a 7mm LED spacer that will slide over the signal pins, to accommodate the recess. The stability pin will just reach the board and can be soldered to provide a bit of support.

I haven't tried the second approach, but if you're willing to give up the stability pins you may be able to use the XLR's normal pins. Here's an example from Kinki, and here's a shot kinda showing the increased spacing. 

I think I remember that the Cardas vertical RCAs were a better length for matching the XLRs, but price is a thing and you'll also need to measure it yourself before making any boards, as their online documentation is not guaranteed to be accurate. 

p_151229_05831 (5).pdf

[Pars 1,597]

Thanks for the info! Yes, I hadn't considered the Cardas jacks, but might. I haven't done any more work on this yet. I need to order the switch to see what effect that has on the spacing.

Edit: Hmmm, I thought I had Vampire's website, but as you mention, I can't find it now. I wonder if something is up with them (as in gone under). Could be a good reason not to use them, although for my application, it is somewhat a one-off. I might want to reuse in the future however, so possibly looking at the Cardas might be wise. I presume it is the GRFA PS2 that you were referring to?

Edited February 15 by Pars

[willsw 0]

I was talking about the PS2, though if you ask Cardas it's actually the GRFA PS A, the replacement for the discontinued PS2. They told me this last March, but the website still has the PS2, not the PS A. I did get a sample from Cardas and made a footprint for it, but it's untested. I see now that you were talking about the DBL PRT in an earlier post, which I'm very familiar with. Right-angle connectors are certainly much simpler if you're combining XLR and RCA, and I'd probably go with angled if you didn't have a compelling reason for the vertical mount. To achieve a double row using the right-angle version of the AEC/Vampire RCA you can alternate mounting them staggered on the top and bottom of the board, which would also reduce the potential width of your board, given the need for nut-tightening clearance. Not really an issue with a single pair, though.

Because of this issue, many manufacturers just wire solder-cup XLRs to the RCA-holding PCB. Since you're trying to avoid the switch wiring and XLRs are very friendly to solder, this may be the easiest option, and the smaller boards are cheaper too. 

A note on the board you posted earlier - I'd recommend flipping the schematic symbol or rotating the switch so that all the traces are short and direct. You've got a lot of unnecessary length and an unneeded via. The datasheet for any switch should also tell you the height for spacing needs. 

If you do find a lower-profile switch that you love, really want vertical mount RCAs, but are willing to have XLRs off-board, there is also this style of RCA, which is probably the best suited for being either PCB-mounted or wired separately. If you look up pictures of Denafrips products, you can see them in action. They actually seem to have transitioned between a few standards of mounting them directly on the board and wiring them to the board. 

[dsavitsk 4,442]

Even if Cardas paid me to use theirs, I'd use a $1.25 part from Mouser instead.