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Audio Attenuator circuit

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Tianfeng:
Hi,

I am new to building stuff and I am trying to attenuate an audio signal used to drive an 8ohm 5w speaker for an arcade cab.  So far I have found that the audio out has a 0-6v swing and I used a 5.62k and 2.2k resistor as a voltage divider to bring the voltage down to 1.66v which is about where I want it incase some boards are quieter. I think this is the proper way to do this but if I am worng please let me know.

 After the voltage divider I am putting it through a capicitor but I can't figure out how to properly calculate the value. I have tried 1uf and 47uf.  The 47 seemed more muddy but I can't be sure. 

When I asked in an arcade forum they just pointed me to pre-made ebay stuff but I want to learn why and how this works as much as I want to get it working right. 

 

Richard Crowley:
Please clarify WHERE you are trying to attenuate the audio signal.  Are you trying to attenuate it at the INPUT to the power amplifier, or at the OUTPUT?  It is not clear why the specs of the speaker are significant here if you are asking about attenuating the "line-level" audio signal going into the power amp.

Why wouldn't you simply use a potentiometer as a variable "volume control"?  Depending on how you are deploying your gadget, you could put  knob on the back of the console for adjusting the volume, or you could put it on the front where it is a user-control.

The larger capacitor will better pass low frequencies (along with the higher frequencies).  When you say that it sounded "muddy" it seems possible that is more a function of the speaker and whatever enclosure you have it in.  There are ways of calculating the value of the capacitor, but you wold need to know the "input impedance" of the next stage (the input of the power amplifier).  It would help if you revealed what you are using for the power amplifier.

Tianfeng:
Ok I can try to provide more details. I am using it as part of a supergun the the there is an onboard amplifier that is set up to drive a an 8ohm speaker and supposedly peaks at 6v. I am trying to bring down the voltage to line level audio after it is amplified.  I read that line level audio was generally 500mv before put into an amplifier or tv but many devices are actually closer to the 2v level.  I don't want to have an adjustable volume but just a consistent output.

EDIT*  The audio amp to drive the signal to the jamma edge is a TDA7240A.

Richard Crowley:
So simply install a potentiometer ("volume control").
Isn't the solution that simple?  Are we missing something here?
A potentiometer is simply an adjustable voltage divider or attenuator.

JPM_AEIC:
I don’t have much to add to this conversation, but I can tell you definitively that Line level audio is 1.23V. This is the voltage level you should be sending to the power amplifier.


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