Saturday, March 16, 2024


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The QuantAsylum QA403 Audio Analyzer features eight female BNC panel mount connectors which provide excellent shielding out to 4GHz (plenty high enough for even the highest frequency digital audio recording). The generator outputs are on the left and the analyzer inputs are on the right. 

The BNC connector is not typically used for audio connections in recording studios so how do you connect this box for testing your audio components which might have RCA-Phono, TRS male or female or XLR audio inputs and outputs?

I've a big believer in learning how to make your own cables but I've never enjoyed assembling BNC plugs and cables.

BNC can be used for a variety of signal types, they're popular for video connections but you'll find them used on a variety of professional equipment of all types. Standard BNC cables are typically a piece of stiff coax cable with identical female BNC plugs on either end.

I was 12 years old when I first saw BNC connectors (pronounced “Bee-En-See”), my friend and mentor, Kent (later known as Dr. K) used BNC connectors in the Ham radio station he built in his parents basement. Dr. K called them "Bince" connectors.  Back in 1964 he had the special stripper and crimping tool needed to reliably assemble a BNC plug onto a piece of coax. Thankfully, today, in 2024 you can buy assembled BNC cables and adaptors for reasonable prices and minimize the pain and learning process.


  • BNC are two conductor connectors, inner conductor with outer shield.
  • BNC connectors are locking meaning they can't come unplugged accidentally.
  • BNC are non-shorting, you can't easily short the conductor and shield together by connecting or disconnecting.
  • BNC are compact connectors.
  • BNC are inexpensive.
  • BNC connectors make reliable connections. 
  • BNC connections provide outstanding shielding characteristics at higher frequencies.

To utilize the BNC connections on the QA403 you're going to need a bunch of different custom cables OR a box of adaptors to use with some standard BNC cables. If I was running a repair-shop I'd probably make some custom cables that would connect easily with the types of products we were repairing most often. In my recording studio I'm faced with a variety of input and output jack configurations on all sorts of equipment so it would require a bunch of different cables if I used custom dedicated cords. 

Using standard off-the-shelf BNC cables with adaptors can get you connected up reliably and allow your QA403 female, panel mount BNC jacks to connect with virtually any piece of audio gear, ranging from “Consumer” RCA-phono connections (male and female) to balanced and unbalanced 1/4” phone connectors along with the professional audio standard XLR (male and female). 

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I have a number of adaptors and cables dedicated to connecting my portable QuantAsylum system into and out of various studio gadgets. I organized my adaptors and connectors into one of these plastic boxes which has multiple separate compartments for sorting. I have my QA403 analyzer kitted-up for portable use and this organizer box for my adaptors makes transporting cables and adaptors with the analyzer system easy.


RCA-Phono Connections

Adapting a panel mounted female BNC jack to an RCA-phono connection is easy thanks to the CCTV industry. CCTV systems use both BNC and RCA-phono connectors so there are lots of adaptors and they're inexpensive. 

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This handy adaptor converts the QA403 BNC connections into standard female RCA-phono connection points, from there you can just use standard RCA-phono cables to get in and out of your DUT (device under test). 

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You could adapt one of your RCA-Phono plug ends into an unbalanced male 1/4” Phone plug with an adaptor like the gray one shown above.

QA 403 Balanced Output (channel 1 of 2)

The left output from the QA403 generator is delivered on two BNC female jacks which are marked (+) and (-), these are identical signal outputs which are out-of-phase with each other. To derive a balanced audio signal from the two female BNC jacks requires a custom cable or some clever use of adaptors. 

As recommended on the QuantAsylum web site I use a Hosa brand splitter cable with RCA-phono plugs on the two loose tip and ring ends and a 1/4” male TRS Phone plug on the other end. These cables come in various lengths, they're reliable and available from a number of retailers. It looks like this:

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Of course you could make a split cable yourself, I've personally built hundreds during my audio career and I can say without shame that it is NO FUN trying to reliably land two shielded cables inside the barrel of a Switchcraft 297 male TRS plug. I don't like soldering on RCA male phone plugs either. I'm completely satisfied with the performance of modern molded cable connections (I've tested several with my QA403 audio analyzer :-).

Another way to get an XLR balanced output would be to make a splitter cable by cutting a molded RCA-to-RCA cable in half and solder the cut ends into an XLR plug. My problem with this is it requires several custom cable/adaptors to accommodate full stereo XLR connections; by using adaptors with standard cables I cut down on custom cables hanging around. 

If you're using the Hosa splitter cable I like to convert the TRS male into a TRS female with an adaptor. Many of the pieces of equipment in my studio offer TRS input and output as well as XLR. 

I've never found a pre-made female-to-female TRS 1/4” adaptor that is reliable beyond two or three uses so I make my own. A heavy duty TRS-female to TRS-female adaptor is a very handy box to have in the studio. Here is one of mine:

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Be sure to read the CAUTIONARY NOTE at the end of this article to prevent possible damage to your QA403.

Here is a how-to-build article on High on Technology. It's a compact aluminum box with Switchcraft 1/4” TRS female jacks installed in each end. These jacks are very reliable, the adaptor is wired tip-to-tip, ring-to-ring and sleeve-to-sleeve. I have been using these since 2011 when I assembled my first few pieces, since then I've built dozens for making various TRS-to-TRS connections in the recording studio. 

Getting Balanced Input/Output connected to QA403 - The Chain Of Plugs And Adaptors – 

Here is the combination I'm going to show you next: 

BNC-to-RCA adaptors on Hosa split cable, TRS-to-TRS box, XLR adaptor of choice

Certainly there are many other combinations of connectors to get an XLR connected to a dual BNC, these are the ones I'm using in my recording studio for testing gear with the QA403.


I bought these small gold adaptors for converting 1/4" headphone outputs to 1/8" plugs in my recording studio but I've also turned them around to use them as a way to feed stereo audio signals from phones, laptops and portable CD players.


The "BNC Two-For" can convert one front panel QA403 jack into two just in case you want to feed an Oscilloscope input simultaneously or possibly a monitor speaker system. Keep in mind you could be polluting your test with ground-loop or other RF interference. 

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You might also like to feed a BNC from a Binding-Post Banana plug, there's an adaptor for that.

You can adapt a BNC cable end directly to an unbalanced 1/4" male phone plug.

Another handy BNC adaptor is the "Female-to-Female" which provides even more adaptor and signal flow options.


There are many paths for connecting the QA403 Audio Analyzer, these are just a few I've implemented for testing and evaluating various pro audio gadgets found in a typical recording studio or live sound situation.

CAUTIONARY NOTE: Don't drive the QA403 generator outputs into a short. If you use a TRS adaptor box like I showed you earlier you could plug an unbalanced guitar cord into the TRS output and this would provide a dead short to the ring connection feeding back to the QA403 on the other side of the adaptor box - Don't Do That!  BE CAREFUL and think about the connections you're making. 

Once you have YOUR box of adaptors and cables together, dig in and start evaluating audio gadgets with the incredible QuantAsylum QA403 Audio Analyzer.

Thanks for reading High on Technology, Good Music To You!

©March 2024 by Mark King, it's not ok to copy or quote without written permission from the author.