Electronics > Beginners

Audio Amplifier

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Audioguru:
Now that you reduced the input to 0.7V does the output still need to be amplified to 10V?
10V RMS is a very high signal level, maybe it must drive a loudspeaker? Then you need a power audio amplifier, not an opamp.

Where does the noise come from, is the intercom used in a noisy factory? If you filter away high noise frequencies then you also filter away the important high frequency consonants sounds of speech.
Background noise jumps up and down during speech when AGC is used. 

staticshock:
I will find out in the next few days about all of that.

Doctorandus_P:
Have a look at simple single chip audio amplifiers:
TDA2030 or TDA2050.

Nowaday's small class D amplifier boards from China / Ebay are also common.

staticshock:
Well I have been updated with new information, but my design is pretty much going back to a blank slate. I'm now required to replicate existing circuits, but modify them for a variable gain. The existing circuits used AD840 op amps, but they are now obsolete. From TI I've found OPA846 as the cross reference, but if anyone knows of another substitute for that op amp, please let me know. Also most circuitry use transformer coupling, which I've never been introduced to. Is there a certain type of transformer I need to use?

HB9EVI:
maybe you should fill the blanks for us.
normally in audio circuits you don't work with variable gain, but you adjust the signal level before the amp by a simple pot.
also I don't understand why to take such rf opamp for an intercom; why aren't some normal TL082/084 not enough? why transformer coupling?

if you want some serious advise you should tell more what we are talking about

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