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  • Mix-Minus Applications

    by Benchmark Media Systems January 01, 1997 2 min read

    Mix-Minus Applications

    The IFA-10 as a Mix Minus

    By Allen H. Burdick


    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

    Closeup of Plasma Tweeter

    Making Sound with Plasma - Hill Plasmatronics Tweeter

    by John Siau June 06, 2023 2 min read

    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.

    Hill Plasmatronics Tweeter Demonstration - AXPONA 2023

    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

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    Benchmark AHB2 Power Amplifier

    Audio Calculators

    by John Siau June 04, 2023 1 min read

    We have added an "Audio Calculators" section to our webpage. Click "Calculators" on the top menu to see more like these:

    THD % to dB Converter
    THD dB to % Converter
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    Benchmark AHB2 Power Amplifier

    System Performance Calculations

    by John Siau June 03, 2023 13 min read

    If an audio system is composed of multiple components, we may have detailed specifications for each component, but we will not know the performance of the combined system without doing some calculations. You may have questions such as these:

    • Will my audio system produce audible noise?
    • Will my audio system produce audible distortion?
    • How will my audio components work together as a system?
    • How loud will my audio system play?

    Use Benchmark's online audio calculators to find answers!

    For example, if we know the output power of an amplifier, as well as the sensitivity and impedance of our loudspeakers, we can calculate the maximum sound pressure level that our system can produce.

    dB SPL (2.83 V,1 M)
    dB SPL

    This application note provides interactive examples that help to answer the questions listed above.

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