Camcorder XLR Audio Adapter/Mixers: XLR Connector

Backside of Neutrik XLR audio connector jack.

Frontside of Neutrik XLR audio connector jack.

Pin 1

Pin 1 direct connection to metal mounting flange

Enclosure piercing pins

• Grounding through Neutrik XLR Connectors

• The Neutrik connectors used for the mixer inputs are designed for superior electromagnetic interference suppression. From the first photo above, notice the electrical connection from pin 1 to the metal mounting flange. The flange is continuous around the entire circumference, for the best shielding and strength. The second photo shows pins that make electrical contact with the enclosure with piercing pins when the connector is fastened to the enclosure. This provides for the shortest path for the cable shield to chassis ground, and avoids having to route RF signals that the shield has protected from the cable conductors near sensitive circuitry or as a part of analog ground. The objective is to keep the RF energy outside of the metal enclosure.

• System Grounding Strategy

• The juicedLink mixers employ a “star” grounding topology. All of the different grounds (analog, power supply, chassis) come together to a single point (to form a “star”), and are isolated otherwise. The balanced mic cable shield which comes in at XLR pin-1, goes directly to chassis ground through enclosure piercing pins on the Neutrik connectors. So, any potential interfering signals that the mic shield has picked up to protect the integrity of the balanced mic signal, never comes in proximity to the mixer circuitry. This is textbook, best practice for grounding in professional equipment.

• Ground to the camcorder enters through the shield of the input mic plug. This is the one and only ground connection to the camcorder, and this has been done by design to ensure that there are no secondary connections to create ground loops. Isolating all other ground contacts (other than the shield of the mic cable) is accomplished by the anodizing the aluminum, isolating the tripod screw from the aluminum chassis with nylon washers, and using a nylon screw as the azimuth pin.

• With the juicedLink mixers, no ground position switch is necessary.

• Why do other camcorder adapter manufacturers have a G1/G2 ground position switch?

• To understand why some other adapters have ground position switches, you need to look at the history of camcorder adapters:

• The dilemma for the early adapters (that connected through the camcorder tripod mount) was that you can’t have ground connections between the adapter and camcorder in 2 different places, otherwise you would get a ground loop resulting in hum/buzz. Keep in mind that this would be a hum/buzz BEFORE ANYTHING WAS EVEN CONNECTED TO THE ADAPTER INPUTS. This has nothing to do with long mic runs in nasty environments (the input Common Mode Rejection Ratio).

• Because of the way the adapters are physically constructed, there was always going to be a ground connection between the adapter and camcorder ground going through the tripod mount (which is not the case for the juicedLink mixers). So, they would cut the ground connection that would go through the adapter output cable, leaving only a single camcorder/adapter ground path through the tripod mount.

• But then, some camcorders introduced didn’t have analog ground connection to the tripod mount (older Sonys, like TRV900). So, if you tried to use the adapter on the new camcorder, there was no ground connection between the 2 at all (an unbalanced signal MUST have a ground reference), and it was ALL hum/buzz (again, before even connecting a microphone).

• So, the manufacturers introduced 2 different models for the 2 different camcorder grounding schemes. But, if you were not using the correct version of the adapter with your camcorder, you needed to do funky things, like file off some of the paint on the adapter and use alligator clips to create your own ground connection. Again, the juicedLink ground never goes through the tripod mount and only goes through the cable (always), so it works with either configuration (I’ve tested it on the TRV900).

• Eventually, the manufacturers introduced a switch to change between the different camcorder grounding schemes, so a single adapter could be used with either.

• So, if you used one of the passive adapters with the G1/G2 position switch on the HV20, one position will sound OK, and the other might be flaky (or worse in some setups). juicedLink always connects ground to the camcorder through only one path, so it is not necessary to have a switch.

• Additional benefit of preamplifier architecture

• Another nice thing about having a preamp is that provides you with more noise immunity in the camcorder/adapter interface … any type of noise. This is because your signal level will be higher going into the camcorder (and the camcorder gain throttled back accordingly), versus a passive type adapter. Let’s say we took a signal generator and injected noise into the output cable going into the camcorder. The juicedLink can provide ~16dB (the max gain) better noise immunity (with the camcorder throttled back 16dB). This is true for any type of noise, including electromagnetic interference (EMI – a concern with low-level unbalanced signals).

• Always observe best practices for earth ground

• So, this speaks to the interface between the camcorder and adapter. As a separate concern, you should always follow best practices for connection to earth ground. Run battery operated when possible. If you have multiple pieces of equipment running from mains, try to run from the same ground return (or power strip).