4 bit volume attenuator
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 9th October 2004, 08:08 AM #1 luvo   diyAudio Member   Join Date: Oct 2004 4 bit volume attenuator Hi peoples, I'm after a little guidance on a small problem I have. My radio (Philips FM91) has a 4-bit volume attenuator that has gone wheels-up. It's unrepairable, and I only have a block diagram for it. i/p--[4dB]---[8dB]---[16dB]---[32dB]-----o/p | | | | | | | | D0 D1 D2 D3 D0-D3 Truth table: 60dB = 1111 (Volume off) 56dB = 0111 52dB = 1011 48dB = 0011 0dB = 0000 (Full volume) I've read on other forums, people reckon a few resistors chucked into a similar array will suffice? I can't see how. As far as I can tell, at least four active devices are required to switch in/out each attenuator!!? Anyways, thats easy enough to do, what I'd like to know is - Is there an easier way? Does a logic chip exist that will do what I ask? This radio is not a high-end audio monster, so quality is not too much of a concern here...
 9th October 2004, 02:00 PM #2 FLZapped   diyAudio Member     Join Date: Oct 2003 Location: Florida Actually, a 4 bit attenuator gives you 16 steps, that's 17 resistors needed for an L-pad divider. Can't you find a suitable replacement at someplace like Digikey? -Bruce
 9th October 2004, 09:08 PM #3 luvo   diyAudio Member   Join Date: Oct 2004 Yes, it is only a 16 step attenuator, using four address bits D0-D3. Depending on which bits are set low, detemines which attenuators (resistors) are switched into the audio path. ie Set D0 and D1 low = 48dB attenuation.

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