Circuitbenders Forum

Circuitbenders Forum => Circuitbending discussion => Topic started by: ELHeath on April 06, 2009, 05:02:44 PM

Title: Not strictly circuitbending, Home Mini System Aux Input Install
Post by: ELHeath on April 06, 2009, 05:02:44 PM
Ello, I own a few circuitbend keyboard but my biggest bugbear is I own a very nice sounding stereo system at home which is pretty much useless as it has no input. I have studio monitors downstairs but they weigh a lot and the leads break if moved around too much. I have a Panasonic SA-PM21 system and I've tried everything from using the radio to using MP3 player radio transmitters.

Would it be easy to install an aux input? Would it just work seperate from the interface of the stereo? Would it just blow up?

All answers on a postcard. I could just buy another stereo but it would be such a waste!
Title: Re: Not strictly circuitbending, Home Mini System Aux Input Install
Post by: Gordonjcp on April 08, 2009, 11:58:14 AM
Has it got a CD player?  You should be able to break into the audio lines from the CD deck and add a stereo jack socket.
Title: Re: Not strictly circuitbending, Home Mini System Aux Input Install
Post by: ELHeath on April 09, 2009, 05:14:23 PM
It has a CD player, a Tape Player and an utterly useless radio (as in it will not pick up a thing).

What would you reccomend for the actual jack plug? How could this be done?
Title: Re: Not strictly circuitbending, Home Mini System Aux Input Install
Post by: ELHeath on April 09, 2009, 05:19:42 PM
The leads between each of the circuitboards and the Tape, Radio and CD player parts are similar to Serial leads that you would find in a computer. I'll trt and get a picture up here sometime.
Title: Re: Not strictly circuitbending, Home Mini System Aux Input Install
Post by: LoFi-Ninja on April 09, 2009, 06:07:43 PM
Either buy one of those casette tape adaptors for mp3 players, or you can inject audio directly to the tape players tape head.. Easy!
Title: Re: Not strictly circuitbending, Home Mini System Aux Input Install
Post by: ELHeath on April 09, 2009, 06:40:44 PM
Tape adapters are not the clearest form (unless they've suddenly got amazing in the last few years)! Anyway, the door closes very tight so that's a no go. How can you inject it directly into the head?
Title: Re: Not strictly circuitbending, Home Mini System Aux Input Install
Post by: LoFi-Ninja on April 09, 2009, 07:31:43 PM
The tape reader head is just a metal box with some coil assembly inside. It's what reads the casette tape. 3 wires should run to it. Gnd & L & R.. So Just cut the vire of some old sterio headphones and solder it accordingly.. Plug your audio source and switch amplifier to tape.. You might need to press play on the tape deck to get sound. Should work just fine. You MIGHT get some distortion, but this should only happen on really old tape decks.. That's why people do this to old walkmans.. Simple distortion/fuzz box...
Title: Re: Not strictly circuitbending, Home Mini System Aux Input Install
Post by: Gordonjcp on April 09, 2009, 07:35:24 PM
You can't really inject the signal into the head, because it's designed for a signal in the order of microvolts and has a massive lowpass filter on it (otherwise everything would sound very tinny).

Work out which are the left and right audio outputs from the CD deck and tap in there.  It's the right level and everything.

Gordon
Title: Re: Not strictly circuitbending, Home Mini System Aux Input Install
Post by: ELHeath on April 09, 2009, 07:47:44 PM
Thanks! Suggestions on a stereo input jack? What am I looking for?
Title: Re: Not strictly circuitbending, Home Mini System Aux Input Install
Post by: Gordonjcp on April 09, 2009, 08:13:17 PM
Stereo jack with break contacts.  The "fingers" go to the amp, the break contacts go to the CD player.  When you push a jack in, the plug will push the fingers off the break contacts.

Have a look at 1/4" jack sockets in your local electronics shop to see how this works.
Title: Re: Not strictly circuitbending, Home Mini System Aux Input Install
Post by: ELHeath on April 09, 2009, 08:39:06 PM
http://www.maplin.co.uk/Module.aspx?ModuleNo=982&doy=1m4&C=SO&U=strat15

Suitable?

Thanks for all the help!
Title: Re: Not strictly circuitbending, Home Mini System Aux Input Install
Post by: deathbender on April 09, 2009, 10:22:55 PM
Looks like it should work. "Break contacts" is the keyword here if you are after the solution Gordonjcp described...
Title: Re: Not strictly circuitbending, Home Mini System Aux Input Install
Post by: ELHeath on April 10, 2009, 12:52:43 AM
Yeah it seems like the most suitable solution, but I'll post up a pic of the wire first.

Says it is 3 break contacts.
Title: Re: Not strictly circuitbending, Home Mini System Aux Input Install
Post by: Gordonjcp on April 10, 2009, 01:32:04 AM
Just the job.  You see how it breaks the circuit when you put a jack in?

If you wanted to break the output of the CD away from the amp and feed that *out* the jack, you'd wire that to the fingers and the amp to the break contacts.  Clever, eh?
Title: Re: Not strictly circuitbending, Home Mini System Aux Input Install
Post by: ELHeath on April 10, 2009, 01:36:52 PM
So in effect, if you wanted to use the CD player you could just wire it back up to the jack? Nice. Here are some photos of the inside:

http://www.autonomouspeople.co.uk/Pics/Inside1.JPG
http://www.autonomouspeople.co.uk/Pics/Inside2.JPG
Title: Re: Not strictly circuitbending, Home Mini System Aux Input Install
Post by: MrSoul on June 11, 2019, 01:41:50 AM
Hi,

Sorry to dig up this post, but I'm on the same project and there are really few people who have made these kinds of modifications.

After watching this video (https://www.youtube.com/watch?v=DTus8kwXA8U) and working on the Service Manual (https://elektrotanya.com/panasonic_sa-pm21e.pdf/download.html), we can see that it is possible to solder a jack on the tuner circuit: TUNER_LCH(5), TUNER_RCH(7), and PORTSEL(1) (which seems to be in bridge with TUNER_GDN(10)) for ground.

I deduce that it is possible to solder a jack on the k7 audio circuit: PB_LCH(6), PB_RCH(8), but for the ground, 9VGND(19), or VREF-(11)+AGND(10)?
Or on the CD drive: CD_L(17),CD_R (15) and D_GDN(12)?

You think I'm right?