An XLR cable adapter

QA40x
1

Hi everyone,

I’m not a fan of the BNC cables. I mainly use the QA403 for commercial amp/preamp/… testing and much of this stuff is unbalanced while some is balanced. This means I use almost exclusively RCA and XLR jack/cables and I never use BNC cables.

I tried making custom dual BNC->XLR and dual BNC->RCA cables and frankly just failed at it. All the BNC connectors I found were designed to use coax and connecting other cables was problematic at best.

Anyone, rather than constantly suffer icky cables I just built a BNC->XLR converter that stays on my QA403 constantly. A few photos->

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I started by 3d printing the front/back panels and supports and did a sanity check - which worked well. Then I milled front and back panels from 2mm aluminum. Note I rear-mounted the XLR adapters to make it easy to replace the front panel for an additional output connector (RCA?).

If anyone wants the models I’m happy to post the Fusion360 design/manufacture files or the .STL 3d printing models.

Mark

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Here’s the result of a quick loopback test with a stock 1/2M balanced XLR cable:

XLR Left
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I made some shielded rca and xlr cables and retested the loopback.

Straight XLR shield connected to output xlr

XLR Left2
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XLR->RC->barrel->RCA->XLR (both are two wire shielded twp). The output uses plus and gnd. The input uses 2,3 balanced input.

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That’s extremely cool.

You could also use three pieces of plastic light pipe drilled through the adaptor plates and up against the LEDs on the QA403 to duplicate the indicators on your adaptor.

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By the way, here is the final configuration with the set of cables I use virtually 100% of the time - other than obvious stock XLR cables.

Note the holder is now connected to the enclosure and it has feet to make it even height.

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Mark,

That’s a cool solution. If it’s going to connect to the enclosure anyway, it could be simplified by losing the center plate and using line BnCs. I would have probably chosen the spring-latch XLR-F instead of the button latch, but that’s a personal choice.

FWIW, Matt, I bought my QA already, but if I had had an equal or nearly equal price option to buy with XLRs, I would have gone that direction.

Dale

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Thanks for the comments. I hadn’t seen the spring latch, I may try that next design.

Mark

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Very interesting!

What kind of BNC-adapters do you use? It‘s not a normal BNC plug, isn‘t it?

Would you sell a complete set for diy to germany?

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It is a standard BNC adapter. This: Superbat BNC Male Plug Nut Bulkhead Solder RF Connector

Shipping to Germany would be more than it’s worth I think. Here’s a view of the bodies - they’re not very complex if you want the models.

image
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The XLR adapters are standard Neutrik sizes.

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Thanks a lot, Mark!

Unfortunately Amazon isn’t shipping these bnc adapters to Germany… There are a lot of female adapters out there, but I found only one male adapter for soldering, but it lacks the ground latch.

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Finally I found a model from Amphenol:

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Last question (I hope):

Whats the lenght of the bolts needed for this construction?

Thanks a lot

Christian

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Hi,

The amphenol part looks fine. You really don’t want it to be able to rotate - which that works for.

Bolt lengths - unlike everything else, I did those by eye and bought a selection of M2.5 hex standoffs. The length is critical if you have a plate for the Bncs (like I do). That measures as about 28mm but I used two standoffs and a nut as you can see in the photo.

The length between the BNCs and XLRs isn’t nearly as critical since the solder wires have some slack in distance. I used 30mm which gave a tiny bit of free space between the connectors. 32mm might be more comfortable.

Mark

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