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Technical Topics => The RF Workbench => Topic started by: Antennae on February 01, 2014, 0303 UTC
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I want to plug my mp3 player into my lm386 amplifier. I learned that just connecting the right and left channels together is a no no. I got a nice circuit diagram from this place under "Stereo to Mono Summing Box:"
http://www.rane.com/note109.html
Is it really necessary?
Are these resistor values good for my wee little mp3 player or are these for something like stage wiring (which might be different as far as I know)?
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Your MP3 player probably won't care if its output are tied together, but if your worried about it, use a 1-10K resistor in series with each channel to sum them together. That's all you really need.
+-RH
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Thanks.
Yeah, I'm worried about it. It'll help me not worry about hurting my mp3 player. They are little, but expensive.
Since I first posted, I consulted the Corsair and Commando wiring and they had one input for sound, but nothing about the combining of the left and right from the music player.
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One of those schematics has a left and right input with series resistors feeding the modulator.
+-RH
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Tried sending you email via this board. Send me a personal email if you can see the info. This is something even I know! Very simple, just a few resistors involved. I can send jpg. You can run that mp3 player at probably 2/3 - 3/4 headphone output and it will work fine.
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Yeah Antennae, as redhat said, your player probably won't care... mine do not. Although I'm sure there are exceptions, I believe that article to be as much opinion as fact. If you need a cheap MP3 feed try this:
http://www.allelectronics.com/make-a-store/item/MP3-1/MP3-PLAYER-W/MICRO-SD-CARD-AND-READER/1.html
These little dudes are Sansa slotmusic players. They use an SD micro card and work GREAT. Very well-made with a metal frame. Also All Electronics sells the same without a card for 2 dollars less. These are WAYYY better than those crappy menu-driven things they sell in the dollar stores and you can't beat the price...
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redhat: Thanks, I could easily have missed it. I also didn't check multiple sites.
moof: Thanks, I sent you a private message.
ff: OK, you said the article has some "opinion." So I've found in every hobbyist group there are opinions that are held religiously, is this one of those?
P.S. Wow, 9 bucks with a card and reader! I have a Sansa with the menu driven crap and its a pain especially when driving a car.
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ff: OK, you said the article has some "opinion." So I've found in every hobbyist group there are opinions that are held religiously, is this one of those?
P.S. Wow, 9 bucks with a card and reader! I have a Sansa with the menu driven crap and its a pain especially when driving a car.
No Antennae, this is NOT held religiously. From an engineering standpoint what the article writer said is true and HE holds that viewpoint religiously. Both channels should be isolated from each other. From a practical standpoint that is often overkill. With low power circuits and modern chips such as those found in a pocket MP3 player the channels usually require no further isolation. If in doubt, err on the side of safety. The link I provided is for the Slotmusic player. There is no menu-driven anything. Just plug and play (and adjust the volume). BTW - I often use these to feed my transmitters, and I hardwire both channels together. Been using them for over a year that way and I've never had a problem...
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Go to Rat Shack, buy a stereo headphone to RCA jack. You now have a monophonic output to feed the transmitter with. Plug the stereo end into your audio source and the RCA end into your patch cord. Plug the other end patch cord into your transmitter, switch the tx on and crank the audio, you're on the air. Nothin' to it, and no soldering.
It will cost you about two and half bucks, plus tax.
Invest in a snap-on ferrite for the patch cord while your there, if you don't have a few around the radio room. Give the patch cord about 3 turns around the core and snap it shut. It will stop rf from creeping back into your audio source.
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ff
Thanks for your response, I understand now why modern, low power players are forgiving. I have enough info to solder in some wires. I checked out your link and I like the player a lot.
Pigmeat
I'll have to get me one of those snap-on ferrites.
I'm being particular because I want the best sound quality I can have. So I'm taking my time before soldering stuff into place.
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I always convert my shows (on mp3) to mono before distributing, to nullify the whole issue.
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Thanks. That's my final decision, I soldered them up last week. I used stereo jacks and soldered the tip (+) and the sleeve (-) . I used 2 jacks, one for a player and one for a microphone.