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 Post subject: Stereo to Mono Adapter
PostPosted: Apr Sun 17, 2016 7:04 pm 
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I have an old TV that I added a mono headphone jack and a bypass switch for the internal speaker. I would like to build the ipod adapter schematic so I can run it to a pair of stereo headphones or an amplifier.

The ipod adapter schematic references a radioshack isolation transformer that you can't buy on their website and they're no longer available from any local radioshack. What are the specs of these transformers so I can order something from digikey? Also this circuit will work in reverse with the way I am intending? Right now plugging in headphones or running to a stereo amp only outputs on one speaker.

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 Post subject: Re: Stereo to Mono Adapter
PostPosted: Apr Sun 17, 2016 8:27 pm 
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That circuits been floating around on the web, for some time. Its an isolated "additive" mixer. One issue, with those, is that the frequency response is dependent on the transformers used. Usually you lose the low end. I find this circuit simpler:

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 Post subject: Re: Stereo to Mono Adapter
PostPosted: Apr Sun 17, 2016 9:07 pm 
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OK. I am using this with a Vectrex game system and do want to keep some of the bass. Sounds a lot better coming through an Amp or Headphones instead of that puny speaker they put in it.

This circuit will work just fine reverse? The way I am intending to use it?


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 Post subject: Re: Stereo to Mono Adapter
PostPosted: Apr Sun 17, 2016 11:55 pm 
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Maraakate wrote:
OK. I am using this with a Vectrex game system and do want to keep some of the bass. Sounds a lot better coming through an Amp or Headphones instead of that puny speaker they put in it.

This circuit will work just fine reverse? The way I am intending to use it?
You don't need anything fancy. Just a mono plug to dual whatever your stereo device is splitter. Such as
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That will output the mono channel to both left and right stereo inputs.


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 Post subject: Re: Stereo to Mono Adapter
PostPosted: Apr Mon 18, 2016 12:07 am 
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I figured as much, but I didn't know if this adapter would be better than that option. It doesn't have to be hi-fi or anything. It's mostly just to listen to atari-like explosion sounds, :)


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 Post subject: Re: Stereo to Mono Adapter
PostPosted: Apr Mon 18, 2016 12:12 am 
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Maraakate wrote:
I figured as much, but I didn't know if this adapter would be better than that option. It doesn't have to be hi-fi or anything. It's mostly just to listen to atari-like explosion sounds, :)
The radio shack circuit won't get you anything, it's for combining stereo into mono. You shouldn't ever tie two stereo OUTPUTs together (like to a mono radio) but driving two INPUTs from a mono channel is fine.


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 Post subject: Re: Stereo to Mono Adapter
PostPosted: Apr Tue 19, 2016 12:16 am 
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Quote:
What are the specs of these transformers so I can order something from digikey?

Hi,
I used a pair of Triad TY-146P line transformers to do the stereo to mono function so that I could attach my laptop PC headphone output to a Bell 2122C monaural hi-fi amplifier. They work great and the sound is great. I posted a demonstration video at http://www.zippcast.com/video/1f1d415ac983f95f445

You can use this circuit in the other direction just fine.

I preferred this approach because of the electrical isolation that it provides. I can't remember if I ordered them from Newark or Digi-Key. It was back in 2012.
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-73


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 Post subject:
PostPosted: Nov Sat 24, 2018 3:10 pm 
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Flipperhome wrote:
shouldn't ever tie two stereo OUTPUTs together (like to a mono radio) but driving two INPUTs from a mono channel is fine.


I have a 'stereo to MONO' adapter for listening to my 8tracks and cassettes and it works well :)

I have always loved MONO,it sounds much better!! (Any stereo record I can find IN MONO I do try to get)


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 Post subject: Re: Stereo to Mono Adapter
PostPosted: Nov Sat 24, 2018 4:07 pm 
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[quote="random73"]
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This looks pretty much the same as the circuit in the OP, but without the 10 ohm resistors. But there's a BIG difference in the two diagrams. One of the windings on the jack side of the transformer is wired in opposite phase from the other when compared to the OP's circuit. This would mean that in one one the two circuits, one stereo channel would be out of phase. Am I seeing this correctly? If so, which circuit keeps the phases correct?


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 Post subject: Re: Stereo to Mono Adapter
PostPosted: Nov Sat 24, 2018 10:33 pm 
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Except for the resistors, they're both connected the same way. It's just the way it's drawn. Notice that in the first diagram, the common lead goes to the same white lead on the transformer primaries. And the secondary connections are identical.


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 Post subject: Re: Stereo to Mono Adapter
PostPosted: Nov Sat 24, 2018 11:40 pm 
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Macrohenry wrote:
random73 wrote:
Attachment:
Combiner.png


This looks pretty much the same as the circuit in the OP, but without the 10 ohm resistors. But there's a BIG difference in the two diagrams. One of the windings on the jack side of the transformer is wired in opposite phase from the other when compared to the OP's circuit. This would mean that in one one the two circuits, one stereo channel would be out of phase. Am I seeing this correctly? If so, which circuit keeps the phases correct?
The transformers are just shown in a different orientation but they're the same phase in both. Follow the phasing dots, not winding orientation.


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 Post subject: Re: Stereo to Mono Adapter
PostPosted: Nov Sun 25, 2018 1:22 am 
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Flipperhome wrote:
The transformers are just shown in a different orientation but they're the same phase in both. Follow the phasing dots, not winding orientation.


Thanks guys. This is why I try to keep orientation uniform when I draw schematics. I know how confused I can get and things not matching only makes it worse. I know, I know, uniform orientation would have made for an uglier schematic in the first one, so I guess the lesson learned here is is indeed not to make assumptions about orientation in drawings.


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 Post subject: Re: Stereo to Mono Adapter
PostPosted: Nov Mon 26, 2018 11:42 pm 
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Here's mine, less chance of screwing it up. :lol:

A 1:10 step up boosts the output nicely.


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 Post subject: Re: Stereo to Mono Adapter
PostPosted: Jan Tue 22, 2019 3:06 am 
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There's three ways to do it.

1. Install a stereo 1/8" jack with the left and right channels of the jack shorted together and use a standard stereo 1/8" to stereo RCA cable.
2. Install a stereo 1/8" jack with the left and right channels of the jack shorted together then use a stereo 1/8" plug and wire one channel to a larger speaker of the same impedance as the original.
3. Take the audio signal from before the amp and feed it to a stereo 1/8" jack with the left and right channels of the jack shorted together and use a standard stereo 1/8" to stereo RCA cable.

1. Will work and will not require any special cable or adapter and will work with stereo headphones.
2. More of a stand alone option so that you are not dependent on an external amplifier and will still allow headphone use.
3. Best signal quality but will not allow headphone operation.


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