Can I use this circuit to control cars stereo volume?

[david90]

volume

how can I use this circuit to control my car's stereo volume if I don't have access to the "line" level output? Can i input the amplified signal into this circuit or would that blow the chip?
**broken link removed**

 

[IanP]

Re: volume

You need to get access between pre-amplifier and power amplifier. This circuit, the DS1669, that is, is basically digitally controlled potentiometer, so it is very likely that if you connect it between amplifier and speaker .. BOOM!!!
According to ts data sheet the max voltages on the RHEOSTAT inputs are (-)V-0.5V and (+)V+0.5V..and (-)V to (+)V max is 8Vdc.
Regards,
IanP

 

[david90]

volume

do all audio amplifier ICs require line level input only? If the u input a source that is already amplified, would u need to reduce the voltage before it could be inputted into the amplifier ic to get more wattage than before?

 

[IanP]

Re: volume

In standard AV applications the audio input of a device would be prepared to take the signal, which is ≈0.775, but from your post it is not clear, where this signal would come from..
Regards,
IanP

 

[VVV]

Re: volume

If by "amplified signal" you mean the speaker signal, then, yes, that would definitely blow the chip.

 

[david90]

volume

yeah amplified signal = speaker signal.

Can I use a simple voltage divider circuit to bring the speaker signal back down to line level, input it into the volume control, and amplify it back up with a homemade amplifier? Kinda wasteful but power is readily available.

 

[IanP]

Re: volume

You can reduce the level by a resistor-based voltage divider, and then feed this signal to DS1669 volume controller, and amplify it again, and feed it to speakers..
It is like a trip around the World, but it will work..
Regards,
IanP

 

[david90]

volume

How do I figure out how much to reduce the voltage of the speaker output?

 

[IanP]

Re: volume

According to the data sheet, the DS1669 can tolerate up to almost 8Vpp of audio signal, if supplied of +/-4V. If you have an oscilloscope you can "see" what is the peak-to-peak voltage from your amplifier. If you don't have it you can use the formula: Upp = 1.41*(PR)½, so for example, for P=20W amplifier at R=4Ω speakers you will have ≈12,5Vpp voltage so you will need to reduce this voltage only something like 1:2 (bear in mind that without load this amplifier can output higher voltages).
Another option is to build a peak detector which will simple be a diode with a capacitor and just measure thos pp voltage and reduce its level accordingly..
Regards,
IanP

 

[david90]

volume

how did u get Upp = 1.41*(PR)½?

 

[IanP]

Re: volume

If P=U²/R and Upp=√2 U ≈ 1.41 * U then Upp=√(2*P*R)
Regards,
IanP