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Old 19th July 2003, 04:41 AM   #1
biff584 is offline biff584  United States
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Default 20 output distribution amp

I'm trying to build an audio distribution amp to split a 4v line level audio signal from a car cd player into about 20 outputs- I work in a store selling car audio equipment and need the distribution amp to demo power amps. I remember seeing a schematic here recently with 4 outputs- pretty simple opamp circuit. Would something simple work for as much as 20 outputs?

Thanks.

Brian.
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Old 19th July 2003, 05:09 AM   #2
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A couple of Gain Clone chips each with 20 x 100 ohm build-out resistors would do the job just fine.

Eric.
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Old 19th July 2003, 09:54 AM   #3
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Quote:
Originally posted by mrfeedback
A couple of Gain Clone chips each with 20 x 100 ohm build-out resistors would do the job just fine.

Eric.
I imagine that the unit is needed so that each power amp can be punched in/out for in-store ABX.

Wouldn't it be easier to get a patch bay, with the added benefit of no actives in the signal path?

:)ensen
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Old 19th July 2003, 10:53 AM   #4
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Default Re: 20 output distribution amp

Quote:
Originally posted by biff584
I'm trying to build an audio distribution amp to split a 4v line level audio signal from a car cd player into about 20 outputs- I work in a store selling car audio equipment and need the distribution amp to demo power amps. I remember seeing a schematic here recently with 4 outputs- pretty simple opamp circuit. Would something simple work for as much as 20 outputs?

Thanks.

Brian.

yes it would. I think either TI or National has a schematic about a distribution amp. Just make sure that you get a stable op amp at unity gain.
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Old 19th July 2003, 12:00 PM   #5
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Err, yeah I'm not sure if the LM GC chips are unity gain stable.
If not, there are TDA series amplifiers that will do the same job.
I have seen a broadcast DA that used a TDA series chip - I forget which one - TDA 1521 maybe.
Switching is a pita construction-wise if a constantly distributed signal to suitable, and more expendive.

Eric.
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Old 19th July 2003, 12:14 PM   #6
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my understanding is that distribution amps are NOT power amps. their job is to essentially split input into many outputs, drive the signal over a reasonably long distance and terminal at a power amp (thus the name).

so you aren't going to use power amps for this.
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Old 19th July 2003, 12:28 PM   #7
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Default Millwood, You Thought Wrong.

Typical DA's provide a means of driving multiple device inputs from one signal source.
One metod is to provide say, 20 opamps each driving an individual output, another method is to to resistively split the output of one amplifier stage that is capable of driving said 20 loads.
Resistively splitting the output from one amplifier provides guaranteed uniformity of the signal, and the resistors ensure that if one output is short circuited the remaining 19 signals are unaffected.
Normal broadcast and PA usage is one amplifier with resistive splitting.
Using an integrated power amplifier provides economical and appropriate output voltage and current capability in one package.

Eric.
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Old 19th July 2003, 01:15 PM   #8
moamps is offline moamps  Croatia
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Default Re: Millwood, You Thought Wrong.

Quote:
Originally posted by mrfeedback
Normal broadcast and PA usage is one amplifier with resistive splitting.
For example?(1in8 or 1in16 with one amp and resistive network)
BSS?LEICH?AKG?RANE?SHURE?SYMETRIX?BERINGHER?
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Old 20th July 2003, 03:20 AM   #9
biff584 is offline biff584  United States
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Thanks for the replies everyone. Can someone direct me to one of the schematics from TI, national, or some other schematic showing a resistive splitter distrubtion amp?

Thanks again.

Brian.
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Old 20th July 2003, 03:47 AM   #10
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Quote:
Originally posted by biff584
Thanks for the replies everyone. Can someone direct me to one of the schematics from TI, national, or some other schematic showing a resistive splitter distrubtion amp?

Thanks again.

Brian.

I am not sure exactly what "resistively" mean. I guess it is simply putting a large resistor in serial with the load and hang it to the output of an amp in parallel with other loads.

I would you will find this types of distribution amps from TI or National as it discourages the sales of their products.
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