Stereo to Mono for Ipod Amp

[niggez]

Ive been trying to solve this problem for ages but can't find a thread answering my questions, so here they are.
I built a ruby amp for my sisters birthday so she can listen to all her Ipod music not just on headphones. I just can't get it to work. One of the problems, I am suspecting, is that the outpot from the Ipod is stereo, and the Input of my little amp is mono. So how do i convert the signal from stereo to mono?? Whats the most simple solution for this problem?

[~arph]

From good to better and bad.

1) Make another ruby and split the signal with a stereo jack.
2) Take stereo jack and use a summing amp config  (search for a simple mixer )
3) Take a stereo jack and use just left or right output..

[ambulancevoice]

you should be able to hear one of the channels
i think the left channel you should be able to hear, since stereo plugs are usually wired

tip = left
ring = right
sleeve = ground

if you cant then its something else, wrong wiring or plug or the circuit itself, or the output is miss wired or something

to convert stereo to mono, you can make a plug with a stereo 1/8" jack and a mono jack
simply wire the left and right channel both to the tip on the mono plug
and the sleeve to the sleeve of the mono

so from stereo to mono its

tip: left and right

sleeve: ground

another thing you can do is build either of these instead (which would be alot more suited to a ipod listening device)
build this stereo amp (this ic is made for these sorts of applications)

or this little mono ipod amp by mac (which according to him is popular with the locals)
http://www.diystompboxes.com/smfforum/index.php?topic=61480.0

[frequencycentral]

Treat her to a Zvex impamp!

[Processaurus]

you should be able to hear one of the channels
i think the left channel you should be able to hear, since stereo plugs are usually wired

tip = left
ring = right
sleeve = ground

if you cant then its something else, wrong wiring or plug or the circuit itself, or the output is miss wired or something

to convert stereo to mono, you can make a plug with a stereo 1/8" jack and a mono jack
simply wire the left and right channel both to the tip on the mono plug
and the sleeve to the sleeve of the mono

so from stereo to mono its

tip: left and right

sleeve: ground

In electronics it's almost never a good idea to connect two low impedance outputs directly together, as one will be doing its darndest to hold the output at a different voltage than the other, making each demand as much current as it can to fight the other.  With a headphone output like the Ipod has, capable of driving (I'm guessing) 32-ish ohm ear buds, that could be a good amount of current, and be hard on the driver chip and the battery.

The simplest solution that will work right is to use a resistor in series with each channel, joining the far resistor ends together (making a "Y") at the Ruby's input, like you do on the front end of a simple opamp summing stage, except we need no opamp.  I'm guessing 2x 470 ohm resistors would work fine.

[Processaurus]

Oh yeah, there might be a mono setting buried in menus in the ipod software.

[ambulancevoice]

you should be able to hear one of the channels
i think the left channel you should be able to hear, since stereo plugs are usually wired

tip = left
ring = right
sleeve = ground

if you cant then its something else, wrong wiring or plug or the circuit itself, or the output is miss wired or something

to convert stereo to mono, you can make a plug with a stereo 1/8" jack and a mono jack
simply wire the left and right channel both to the tip on the mono plug
and the sleeve to the sleeve of the mono

so from stereo to mono its

tip: left and right

sleeve: ground

In electronics it's almost never a good idea to connect two low impedance outputs directly together, as one will be doing its darndest to hold the output at a different voltage than the other, making each demand as much current as it can to fight the other.  With a headphone output like the Ipod has, capable of driving (I'm guessing) 32-ish ohm ear buds, that could be a good amount of current, and be hard on the driver chip and the battery.

The simplest solution that will work right is to use a resistor in series with each channel, joining the far resistor ends together (making a "Y") at the Ruby's input, like you do on the front end of a simple opamp summing stage, except we need no opamp.  I'm guessing 2x 470 ohm resistors would work fine.

strange since ive done it before (plugged my ipod into my bass amp) and it worked perfectly fine

[grapefruit]

strange since Ive done it before (plugged my ipod into my bass amp) and it worked perfectly fine

Well, it might seem to "work" but as Processaurus said it's not a good idea. Imagine if one channel has no audio signal and the other channel is blasting out a high level signal (not uncommon with stereo music). If you have the outputs joined together the channel that is trying to output signal is being slammed into the low impedance output of the other channel. It can't be doing any good for the signal level, quality, or the output amps. A couple of series resistors is all thats necessary to make a reasonable mixer for this application. It's not worth the risk. I often use 1/8 watt resistors and fit them inside the plug.

Depending on the lead you used it either "worked" because you only had one channel connected, or they were being slammed together as described above.

I'm not having a dig, just explaining that because it works doesn't mean it's a good thing to do.

Cheers,
Stew.

[ambulancevoice]

just as well, i lost the damn thing anyway!