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I am trying to make my own cassette adapter that will help me play my music on my iPod through my car stereo system that supports only cassettes. For that I've bought a 3.5mm earphone jack and a cassette player head unit. Here's the layout:

enter image description here

As you see, the head unit has only 2 pins. But the jack has 3 - one for left and right each and one for grounding. Now what do I do in this case? How do I connect three wires into to pins on the head unit? Thanks in advance.

ADDED

Here's the head from the other side enter image description here

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  • \$\begingroup\$ Is that a mono or stereo head you have bought? \$\endgroup\$
    – HandyHowie
    Oct 14, 2015 at 10:28
  • \$\begingroup\$ Hmm, that is a really good question. I don't really know. I didn't think of asking. But there was no other one. And the seller didn't bother to ask. \$\endgroup\$ Oct 14, 2015 at 10:28
  • \$\begingroup\$ I believe stereo heads have 4 connections. \$\endgroup\$
    – HandyHowie
    Oct 14, 2015 at 10:30
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    \$\begingroup\$ @ricardomenzer, I've added the picture you mentioned. Sorry, that's the best focus I could get. \$\endgroup\$ Oct 14, 2015 at 12:24
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    \$\begingroup\$ Either pin. And if there are only 2 pins it's a mono head. (Confirm this by measuring there's a resistance between them). If it's an erase head, the larger gap may be an advantage. If a replay head isn't aligned within a micron of the player's head you'll lose quality - 10 microns off and you'll probably hear nothing at all, \$\endgroup\$
    – user16324
    Oct 14, 2015 at 13:23

4 Answers 4

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There is a lot more to a tape player than just the tape head. Tape heads are not meant to connect directly to a regular preamp or even a microphone input.

The proper circuit inside a tape player would probably consider the output of the tape head a differential signal. The head's case would be grounded, and the two coil connections treated as equally as possible until after the differential to single ended conversion. After that there will be some frequency shaping and amplification to line level. Only then is the signal ready to be connected to other equipment that the jack you show would plug into.

A tape head and a plug are a long way from a tape player.

Just because you wire a signal to a standard plug doesn't mean that signal magically has the characteristics of what the plug is intended to carry.

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Apparently you already have a sound source, and want to "inject" that into a existing tape player so that the tape player thinks it's playing a tape but is actually playing the signal the tape head is being artificially stimulated with. That's such a bizarre thing to want to do that I didn't realize that's what you wanted on initially reading your question.

The first obvious solution is to not try to fake out the tape player. This player most likely puts out a line level audio signal that goes to a power amp somewhere. Tap into that directly. Your iPod should be able to drive that.

If you really really want to go this bizarre route, then you can drive the tape head you have from the iPad output and hold it right up against the pickup head in the tape player. However, there will be some problems with this:

  1. The frequency response will be a mess. The signal written to magnetic tape deliberately has the high frequencies emphasized. This is so that high frequencies can be attenuated on reading, which helps with overall signal to noise ratio. The same thing was done with old vinyl records, although the frequency profile are different between the two. It's been many years since I've dealt with audio tape electronics, but vaguely remember that the tape head frequency profile was called something like the "NAB" standard, and that for records the "RIAA" standard.

  2. Getting the drive level right will be tricky. The tape head probably has higher impedance than what the iPad is intended to drive, so the iPad won't care. The tape head itself is just a electro magnet electrically, so it should be easily able to take the little power the iPad can put out. However, the pickup signal from a real tape head is quite small, and it will be easy to overdrive the pickup head in the tape player. The coupling will also vary significantly with the placement and size of gap between the two heads.

You might be able to kludge this up if you look up the appropriate frequency shaping (NAB standard?), then add appropriate resistors and capacitors between the iPad output and the tape head.

Again, tapping into the line level audio signal between the tape player and the power amp makes a lot more sense.

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  • \$\begingroup\$ Olin, he's trying to inject music into the tape head and then position said tape head in front of the tape head in his car stereo. You can buy em for next to nothing of course! \$\endgroup\$
    – Andy aka
    Oct 14, 2015 at 10:46
  • \$\begingroup\$ Sorry, @Olin, but I've just got what I need from ebay yesterday for just a dollar. It indeed does what I need to do. The only thing is the sound quality is poor which made me think I could do it on my own. The cassette adapter I got from ebay also has a head with two pins. \$\endgroup\$ Oct 14, 2015 at 10:49
  • \$\begingroup\$ @Andyaka, yes you're absolutely right that I want to position this hed to my car tape head. And yes, they're really cheap. I'm just trying to do it on my own. \$\endgroup\$ Oct 14, 2015 at 10:51
  • \$\begingroup\$ @Andy: Oh, I thought he was trying to make his own tape player. \$\endgroup\$ Oct 14, 2015 at 11:32
  • \$\begingroup\$ Bit of an amusing indictment on those up-voting your answer!! \$\endgroup\$
    – Andy aka
    Oct 14, 2015 at 11:38
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Well as you seem to be struggling with the concepts you can get all the parts you need from here: -

Yes I know it's already assembled into what you want but you can: -

  • Review the performance
  • Strip it down
  • Learn from the process
  • Then rebuild it or put your own parts in etc..

enter image description here

There is an even cheaper one here (£1.68)

enter image description here

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  • \$\begingroup\$ It amazes me that there are actually commercial products out there for this kludge. I'm surprised there are enough ancient tape players still out there in systems that don't have some kind of obvious auxiliary audio input. +1 \$\endgroup\$ Oct 14, 2015 at 11:56
  • \$\begingroup\$ @Andy, I've already gotten this one from ebay. :) It's just the sound quality is poor. I think this is because of the low quality head and bad wires. So I thought I'd buy my own jack and head to build it from scratch. \$\endgroup\$ Oct 14, 2015 at 12:00
  • \$\begingroup\$ @MikayilAbdullayev You may be able to improve the quality by slightly adjusting the alignment of the head in the one you bought. I have seen people use these that sound OK. \$\endgroup\$
    – HandyHowie
    Oct 14, 2015 at 12:32
  • \$\begingroup\$ :) Thanks, I'll try that. But still I would love to have made one on my own. \$\endgroup\$ Oct 14, 2015 at 12:39
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If you want to build the tape head coupler then it better sound better than the bought one .Remember that the standard tape head preamp inside your cassette player has equalisation for the recording and the tape itself.You will want equalisation which will be different to RIIA but could be reasonably approximated with simple passive components .You could consider a stereo tape head .A worn one from a dead tape deck will do .The stereo heads that I have seen have 4 terminals .To get any stereo seperation you will want to adjust the Azimuth accurately.Maybe you could use the Azimuth adjustment screw assembly from the dead tapedeck.You should adjust the input level to avoid overloading the tape preamp ,perhaps a pot on the tapehead would suffice.Once this is done you should get really good SNR because there is no tape moving .

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Finally I could do what I needed so I thought I'd share it with you. As my question was focused on how to connect 3 wires coming from audio jack to 2 pins on the tape head, I'll try to stick to that purpose only. So, first I tried doing what @ ricardomenzer suggested: soldered L & R channels to those 2 pins separately and connected the grounding to a metal spring that I found on the cassette body. Sadly, it didn't work. I then took the L and R wires and soldered them together to one pin and the grounding to the other and voila, it worked. And believe me, I now get decent sound quality. Much smoother than the one I purchased online. Thank you all for your help and effort.

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  • \$\begingroup\$ I wouldn't short the two channels together. \$\endgroup\$
    – crasic
    Oct 15, 2015 at 2:03
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    \$\begingroup\$ Yeah, that is indeed short circuiting but how/why does that work? \$\endgroup\$ Oct 15, 2015 at 4:11
  • \$\begingroup\$ The degree of ungood depends on the output impedances and output coupling of the headphone amps. I suspect apple makes it fairly robust. Otherwise I would expect some distortion due to the mixing as stereo channels do jot carry identical signals. have you tried just using L or R ? \$\endgroup\$
    – crasic
    Oct 15, 2015 at 5:32
  • \$\begingroup\$ No, I have not. \$\endgroup\$ Oct 15, 2015 at 5:37
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    \$\begingroup\$ Shorting the two L and R wires is not a good idea. At least put 10 Ohm resistors or so in series with each. Did you look up NAB and add the frequency shaping network? If not, you'll get a lot more bass than high notes. Resistors will be required with the network, so that gives you the opportunity to put some resistance between the two channels so that they are not shorted. \$\endgroup\$ Oct 15, 2015 at 10:48

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