Passive low-value audio pads

I've often had to knock up audio attenuators to make music gear (which is typically +4dBu for zero level against 0dBu for broadcast) and my usual m.o. is to approximate everything around a 10k potentiometer; typically 100ohm sending impedance, 10k ohm terminating impedance and an H-network for balanced lines and a T-network for unbalanced. You can find numerous examples online.

So - all credit to my colleague Matt for saying "..no, no - let's do it properly";

 

So, for a variable 1.5 -> infinite pad you need Z1 and Z2 at 390 ohms and a 5K potentiometer. 

Blow me down, the 5k pots arrive with their wipers at the centre position and all six that I've made so far have been bang on 2dBs at that centre point. It pays to be precise.

Engineer's Bench - new podcast "Custom Hardware 1: Electronics and Arduino"

Hugh and Phil talk about the need for custom made boxes and panels. They talk about the metalwork as well as circuit details used and wind up with a review of the Arduino platform

Find it on iTunes, vanilla RSS, YouTube or the show notes website.

Tricaster tally-light interface for EX3s

One of my favorite parts of the job is prototyping and making little interface units so that equipment from different manufacturers can talk to each other.

This gadget allows the Tricaster TXCD850 studio production system to light the tallies on Sony EX3 cameras; although the Tricaster has "wet"-style GPI outputs it can drive the 12V needed for the lights. So, simple buffer circuit with relays to drive the studio tallies;

There are some photos in a Facebook album - click the title link.