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Topic: Input/Output gain matching |
Mark Herrick
From:
Bakersfield, CA
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Posted 20 Sep 2001 5:24 am |
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Can someone explain to me the concept/theory of matching input and output gain? I'm talking about balanced/unbalanced line inputs/outputs.
I am working mostly with video equipment, some of which has balanced audio output at +4dB and some unbalanced at -10dB.
The mixer I am using has adjustable gain control on its inputs and outputs.
The question is, and its always been confusing to me, if your output gain is +4bB, what do you set your input gain to in order to get the best level without distortion? Same question for -10dB.
If there is any info on the web that explains this without having to have a degree in electrical engineering to understand it, please point me to it.
Thanks. |
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Jack Stoner
From:
Kansas City, MO
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Posted 20 Sep 2001 6:32 am
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| This is one for Blake Hawkins. Blake is a retired engineer from WSB-TV. |
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Blake Hawkins
From:
Florida
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Posted 20 Sep 2001 9:53 am
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Jack, Thanks for the plug.
Mark,
Many professional videotape recorders operate with +4dbm, 600 Ohm balanced outputs.
The line inputs on most professional audio equiment will operate with a +4dbm input, which allows you to connect the output of one piece of equipment to the input of the other without having to worry about matching.
-10 db is usually used in unbalanced consumer or "pro sumer" equipment.
Generally, your maximum clean audio output, that is +4 dbm,will be achieved when the VU meter,or other volume indicating device is reading "0" (On analog meters,this is about 2/3 scale.)
The input level which will give you this, depends on the design of the amplifier.
If you are using a professional microphone, that level might be -55 dbm.
It could also be -10, -20,+4 or +8. That's why there are attnuators on the inputs of audio consoles..to adjust for a variety of sources.
This is just a brief sketch...audio,recording, broadcast, and sound reinforcement are complicated subjects, and the deeper you get the more questions you will have.
If you have a specific set up, please E Mail me and I'll try to help you with that.
Ultimately, most all audio and video equipment will work together, it just requires some tweaking.
You might find a copy of "Sound System Engineering" published by Howard Sams or the "Audio Cyclopedia",an older Sams Publication in the local library. Those books have detailed information on the how's and why's of audio engineering.
Blake[This message was edited by Blake Hawkins on 20 September 2001 at 10:54 AM.] [This message was edited by Blake Hawkins on 20 September 2001 at 10:59 AM.] [This message was edited by Blake Hawkins on 20 September 2001 at 11:02 AM.] |
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John Paul Jones
From:
San Diego
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Posted 20 Sep 2001 6:27 pm
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Mark,
Also, pick up a copy of the September, 2001, "Electronic Musician" at your favorite newsstand. Starting on page 36 is a great article entitled, "Staying Out Of The Red".
It's all about gain matching.
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John Paul Jones
GFI U-12
Evans FET500 amp
ART T2 effects
HM-4 harmony machine
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