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I have a cassette in my car, I was using a cassette-aux adapter to play music through my phone. It looks like this:

enter image description here

After searching a bit about how it works, I found out that it's nothing but a tape head that is connected to an aux cable. By having the two tape heads close to each other, the signal is transmitted from the first to the other.

I believe this will pick up some noise along the way, so I decided to solder the aux wire directly to the cassette where the tape head is soldered. This way, I don't have to use tape heads at all and have a cleaner signal.

When I opened the cassette, I saw that there are 6 points to solder to:

  • RL (Rear Left)
  • RR (Rear Right)
  • FR (Front Right)
  • GND (Ground)
  • FL (Front Left)
  • COM (Common)

I'm not sure if I've understood correctly.

Here is what I found: enter image description here

I'm planning to solder the aux cable as follows:

  • Right to RR and FR
  • Left to RL and FL
  • Ground to ??

Where should I solder the ground? Should I solder it to both GND and COM?

How should my wiring be?

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    \$\begingroup\$ Without a full schematic and/or some reverese engineering, no one can tell you anything. Compact cassettes have only stereo tracks so Left and Right. Why would there need to be Front and Rear for a stereo signal? I know: it is not the signal from the cassette player's input, it an internal signal going to the speakers or speaker amplifiers. Connecting to this point might not work, it might be an output (not an input) and it might damage whatever you connect to it. \$\endgroup\$ – Bimpelrekkie Apr 17 at 14:50
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    \$\begingroup\$ Most likely that is not the tape head input. Even if it is, the voltage levels from the phone are way too high compared to tape head signals, so you can't just connect it directly. Even if you attenuate the signal to tape head leveks the next problem is that tape head input would most likely have circuitry to equalize the tape head signal to have flat frequency response, but that applied to direct audio signal that already has flat frequency reaponse would sound poor. \$\endgroup\$ – Justme Apr 17 at 15:06
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    \$\begingroup\$ If that really is the head connector, then I’m guessing the F is forward and R is reverse. Presumably your player can automatically turn the cassette over by reversing the tape. Your head will have 2 stereo pickups in it. \$\endgroup\$ – HandyHowie Apr 17 at 16:13
  • \$\begingroup\$ I have to say that I've done it once. I didn't even know then what each wire will correspond to (didn't see the text). I connected only 3 of them (don't remember which) and the sound worked nicely. the next day, the sound got lower. It kept getting lower. I tried using the tape instead since it had a higher sound but it wasn't working at all. I decided to desolder the wires and all of a sudden it worked again. \$\endgroup\$ – StackExchange123 Apr 17 at 16:19
  • \$\begingroup\$ @HandyHowie Yes, that's very likely. It actually does that. \$\endgroup\$ – StackExchange123 Apr 17 at 16:20
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I would recommend finding the schematics for this. Because it could be the speaker outputs. Attaching to the tape head circuit without modifying it might cause failure due to the line signal coming out of the phone is several times greater than the signal that is produced on a tape head. Also there are other things, like cassette present switch, actuated by the basket assembly, that without it defeated, it wouldn't allow the unit to switch to the "cassette".

Other things you should be aware of, is you need to use coupling caps between the phone and the stereo, mainly because phones don't isolate their signal, and a small amount of voltage is present on the signal lines on the phone jack.

COM is the signal common, or signal ground (which is not a correct term). It is different than DC ground or GND. These are different things. COM refers to a common to an AC signal (in electrical power, it is the same as the neutral or white wire) Some circuits tie DC GND to Signal COM, some don't have them referenced at all.

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