Fig. 2: A surplus Tektronix Digital Audio Monitor … At the Radio America Network in Arlington, Va., Director of Engineering Fred Gleason and Production Director Alan Peterson often must troubleshoot remote host mixer issues from afar.
Small mixers are populated with aux sends, tape-to-mix functions and other controls that can be confusing to a layperson. Thus a host may mistakenly hit a button or raise a fader and kill the backhaul or send themselves into a runaway echo over the air.
Fig. 1: Highlight and color-code essential controls to simplify operation.
Recently, a New York-based show host began to use a Comrex BRIC, which doesn’t have a built-in mixer in its interface. Therefore, a separate mixer was required, but Gleason and Peterson were intent on keeping things simple for the non-technical host. They then determined what basic functions were needed, bought an inexpensive Behringer two-mic mixer and created a mask to cover the mixer faceplate. This isolated only those controls necessary to get the job done at the host end.
Peterson diagrammed a simplified control scheme for the host and went trolling for colored knobs in the parts bin. Meanwhile, Gleason measured the placement of the controls and jacks and created a printed overlay in a Linux CAD program.
Fig. 3: … feeds a video monitor for color display of your audio. The “no-touch” controls are in a red-outlined box and have red knobs. The mics are on a pair of nice, safe beige knobs. All sources feeding the headphones have gray knobs and are outlined in a blue box. There is one great big yellow MASTER level control rounding out the front panel, as seen in Fig. 1.
The overlay also includes arrow pointers, showing where critical controls such as pan or aux send should be set to work properly. Any knob not necessary for the task is unlabeled and can be ignored, or in the case of the EQ controls, set up by the host and “spiked” using a Sharpie-brand marker.
Most of the jack field is also ignored, with only the essential ones plainly labeled. Cables are similarly labeled — for example, “Aux Out” on one end and “BRIC L In” at the other.
Fig. 4: A compact lightning detector is mounted in a clear case. Everything was packaged, along with IKEA-like instructions, and sent to New York. Now when there’s a problem, the board operator simply asks the host whether power is on and whether a certain colored knob is turned up or down.
Thanks, Alan and Fred, for sharing your method of simplifying remote broadcasts.
Alan is willing to send readers a sample copy of the instruction sheet, along with photos.
Fig. 5: The detector was modified to operate with “D” cells. Univision’s San Francisco Chief Raul Velez found a used Tektronix 764 Digital Audio Monitor, shown in Fig. 2, for around $300. It’s a real bargain, considering this instrument sold for more than $5,000 new.
Raul uses his 764 to monitor his stations’ digital audio quality. The instrument can monitor four channels, but if you’re only monitoring two, the third and fourth channels can display the sum and difference of the first two.
This is really helpful when you connect the monitor’s VGA output to a video monitor, as seen in Fig. 3. The result is a full-color display of what your audio is doing. There’s even a headphone jack and volume control.
Given the comments I’ve received about the Franklin Lightning Detector, featured in the Aug. 1 Workbench, I thought I’d include a couple of new photos from Ron Gnadinger.
Fig. 4 gives you a perspective of size of the instrument. That’s Ron’s wife Penny Marie posing with the detector. In Fig. 5, you can see the modification that Ron made to accommodate two “D” cell batteries.
It goes without saying, but we’ll say it anyway: Electrolytic capacitors will start to go bad after about seven years.
In audio equipment, the result is usually noticeable hum. In this day of microprocessors, however, AC ripple on the DC supply lines can cause all kinds of wacky problems.
So if you have an operational issue, take a ’scope to the supply rails and look for ripple as your first troubleshooting step.
Motor start capacitors, found in large air conditioning compressors and air handlers, also can fail with time. Look for a bulging insulator that surrounds the capacitor contacts.
Reading Workbench is like taking a college course in hands-on radio problem-solving! Contribute your ideas, help your fellow engineers and qualify for SBE recertification credit. Send tips to firstname.lastname@example.org.
John Bisset has spent 44 years in the broadcasting industry He handles West Coast sales for the Telos Alliance. He is SBE certified and is a past recipient of the SBE’s Educator of the Year Award.