I have this electronic talking toy with a "ceramic speaker" (or whatever it's called) and want to create a line out socket so I can connect it to an audio system, but I'm having problems getting a good sound. The "speaker" looks similar to this picture I found by doing a google search:
and is marked as follows: Murata VSB41D25-07AR
I've searched on the web for it, trying to get some specs, but to no avail (I did find Murata.com, but that part is most likely outdated and not available any longer since the toy is from the early 80's). I've tried measuring the resistance across the "speaker", but nothing comes up on my multimeter! Must have an infinite resistance or something strange is going on ;-)
Then I disconnected the speaker from the toy's circuit board and connected a jack socket in its place. The signal was way too loud, but I got the right level by connecting 440K Ohms worth of resistance (two
220K Ohm resistors) along one of the signal paths. Still, the sound isn't quite too my liking. I believe I need to filter out some bass. I might possibly also need to raise the treble a bit, but I'm not sure about this yet. But I definitely have to remove some lower frequencies. I know that a filter involves resistors and capacitors, but other than that I'm clueless and have spent a lot of time playing around with different combinations, but not really getting anywhere, so what do I do? This is what I've done so far:ORIGINAL CIRCUIT:
----------------->------ audio | out O piezo-ceramic speaker
|----------------->-------
NEW CIRCUIT:
----------------->-------------------------------------------------->
audio line out out
----------------->---------------o---xxxx----o---xxxx-------->
220K 220K