Mix-Minus Applications
The IFA-10 as a Mix Minus
By Allen H. Burdick
Introduction
Radio talk shows are currently enjoying unprecedented success. Witness the phenomenal success of hosts such as Dr. Dean Edell, Rush Limbaugh, Larry King, not to mention comedy car repair experts. Is it any wonder that local hosts are clamoring for the limelight as well? If your station has plans to add a talkshow, you will face the problem of creating a mix-minus, a signal that returns all of the program audio, except the caller's own voice, to the caller. Otherwise, echo, caused by Telco system signal delays, can confuse the caller.
If you have a production console with auxiliary buses that can be assigned to create a mix-minus, you are in luck. However, most simple on-air broadcast consoles do not have that luxury. And note that it takes one auxiliary mix-bus per phone line to create the mix-minus within the console. The IFA-10 is the answer for a simple two or three phone line talk show mix-minus. The IFA-10 is a 4 IN by 4 OUT assignable mixer, using removable internal jumpers to create the desired mixing array.
Figure 1.0 above shows a block diagram of a mix-minus system for use with a stereo console, with the IFA-10 downstream from the console. All of the audio for the host and local guests is mixed in the console. The output of the console is fed to the IFA-10 at the Program Left and Right input positions. By following the schematic diagram you will see that the program audio follows across to the respective Program outputs. Additionally, telco audio is mixed with program audio. At the Tel Line 1 and 2 outputs you will see that they receive the program audio and the audio from the other Tel lines, but not audio from their own line. Of course you will need a Telco "Hybrid" for each of the phone lines and appropriate controls for the phone lines. Gain control for the incoming telco levels is also important. Metering at the program outputs is a must. Figure 2.0 below shows the configuration for a mono mix-minus and Fig. 3.0 shows what can be done by interconnecting two IFA-10s.
Larger mix-minus systems are easily possible using System 1000™ technology. For example, we recently designed a 48 by 20 system for one customer and we can do the same for you!
Also in Audio Application Notes
Audiophile Snake Oil
The Audiophile Wild West
Audiophiles live in the wild west. $495 will buy an "audiophile fuse" to replace the $1 generic fuse that came in your audio amplifier. $10,000 will buy a set of "audiophile speaker cables" to replace the $20 wires you purchased at the local hardware store. We are told that these $10,000 cables can be improved if we add a set of $300 "cable elevators" to dampen vibrations. You didn't even know that you needed elevators! And let's not forget to budget at least $200 for each of the "isolation platforms" we will need under our electronic components. Furthermore, it seems that any so-called "audiophile power cord" that costs less than $100, does not belong in a high-end system. And, if cost is no object, there are premium versions of each that can be purchased by the most discerning customers. A top-of-the line power cord could run $5000. One magazine claims that "the majority of listeners were able to hear the difference between a $5 power cable and a $5,000 power cord". Can you hear the difference? If not, are you really an audiophile?
Making Sound with Plasma - Hill Plasmatronics Tweeter
At the 2023 AXPONA show in Chicago, I had the opportunity to see and hear the Hill Plasmatronics tweeter. I also had the great pleasure of meeting Dr. Alan Hill, the physicist who invented this unique device.
The plasma driver has no moving parts and no diaphragm. Sound is emitted directly from the thermal expansion and contraction of an electrically sustained plasma. The plasma is generated within a stream of helium gas. In the demonstration, there was a large helium tank on the floor with a sufficient supply for several hours of listening.
While a tank of helium, tubing, high voltage power supplies, and the smell of smoke may not be appropriate for every living room, this was absolutely the best thing I experienced at the show!
- John Siau
Audio Calculators
We have added an "Audio Calculators" section to our webpage. Click "Calculators" on the top menu to see more like these: