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Step 9It didn't work, so now add bigger resistors
Ok the 150 Ohm wasn't enough; the sound is still distorting a bit. I'll try adding larger resistors in series. For testing I just soldered them in just sticking out until I find the right size. I first tried adding 470 ohm resistors. After trying it, it didn't seem to make much difference. Next I tried 3000 ohm resistors, but still hardly any change. Next I'll try 10k ohms.
Update 10-07-07
Adding resistors didn't seem to be helping; then I got a suggestion from another great Instructables user, unknownuser2007 He suggested that instead of trying to use resistors to drop the level of the headphones output of the MP3 player, I could try bypassing the cassette head preamp IC like he did in his instructable. A great idea!! Thanks unknownuser2007!
The tape head wires (which I am using as the input from the MP3 player) are attached to the circuit board and traces ran from there to an LA3220 IC chip (see second pic). I looked up this chip on at a great Data Sheets website (see third pic) and found that it is an Equalizer Amplifier that is apparently acting as a preamp for the tape head.
There's another IC, an LA7769 (fourth/fifth pics) whose output goes straight to the speakers. This IC is apparently the main, higher power amplifier for the speakers.
"OK", I thought. "Great; its just what I need to amplify the headphones output of the MP3 player! I'll just move those input wires straight to the input of that IC".
Well, it worked, but then the sound was very loud all the time, even with the MP3 player's volume set at its lowest setting of "1"...bummer..so close!!
Well, one last idea....see next step
Update 10-07-07
Adding resistors didn't seem to be helping; then I got a suggestion from another great Instructables user, unknownuser2007 He suggested that instead of trying to use resistors to drop the level of the headphones output of the MP3 player, I could try bypassing the cassette head preamp IC like he did in his instructable. A great idea!! Thanks unknownuser2007!
The tape head wires (which I am using as the input from the MP3 player) are attached to the circuit board and traces ran from there to an LA3220 IC chip (see second pic). I looked up this chip on at a great Data Sheets website (see third pic) and found that it is an Equalizer Amplifier that is apparently acting as a preamp for the tape head.
There's another IC, an LA7769 (fourth/fifth pics) whose output goes straight to the speakers. This IC is apparently the main, higher power amplifier for the speakers.
"OK", I thought. "Great; its just what I need to amplify the headphones output of the MP3 player! I'll just move those input wires straight to the input of that IC".
Well, it worked, but then the sound was very loud all the time, even with the MP3 player's volume set at its lowest setting of "1"...bummer..so close!!
Well, one last idea....see next step
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