Doug Self Preamp from Linear Audio #5


2018-09-06 4:09 pm
The BOM specifies this for the PCB side, AMP which is TE now.

The BOM doesn't say btw which one to use on the cable side.

A matching one for the cable would be Mouser p/n 571-2-215882-0.


2018-09-06 4:09 pm
BUILDERS NOTE: * XLR Pin1 Grounding *

Note that the IO PCB that I delivered ties pin1 to the internal circuit ground. This is not an uncommon practice for consumer gear and works as expected 99% of the time. If your desire is to ground the XLR Pin1 to the chassis you must use a different XLR connector than the one specified in the BOM. Instead use an XLR whose pins extend straight out the back rather than down to the PCB. Doing this allows you to route pin 1 to the chassis using a short wire. You will also need to run short wires between pins 2 and 3 to the PCB.
There are Neutrik connectors where all 4 contacts are independently routed out, regardless if they are horizontally or vertically mounted, made especially for this purpose. Like the standard NC3FAV ties pin1 to chassis (pin4) but the NC3FAV2 has all 4 contacts routed out independently.
This is why Neutrik is simply preferable than Amphenol or any other brand for XLR connectors. Not to speak that the same Neutrik's are available as well with the whole ring made out of metal for making a 100% EMI shield around the connector itself (compare NC3FBH2 to NC3FAH2 for horizontal mount, denoted by "H" or NC3FBV2 to NC3FAV2 for vertical mount, denoted by the "V"). The "2" denotes that pin1 is independently routed out and not tied to pin1. Then, on the PCB do whatever you want, have a configurable jumper, etc.

The male MAV has always 4 separate pins on the back.
And same play here with MAV and MBV or MAH and MBH.

"M" stands for male, "F" stands for female, easy not.

I noticed the Amphenol XLR connectors in the BOM - I would never use those, but NC3FAH2 and NC3MAH or the more expensive (pin compatible and) 100% EMI shielded NC3FBH2 and NC3MBH - they all are horizontally mounted and with separated pins for ground and chassis on the solder side. Maybe the IO PCB have to be remade.
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