[antonow]

I know very, very little about electronics. They probably shouldn't have even given me a password to this board.

I'm trying to bring "an invention" that I've been thinking about to life. It would allow a person to "sing along with their ipod". There is an image below. Please be very forgiving.

This is only meant to OUTLINE the idea, not the exection.

> I have no real understanding of electronics, but it seems like I should be able to mix (1) the signal coming from my ipod with (2) a signal from a mic.

> In my consumer-radio-shack-world the signal would come from a clip on mic ($25) that would plug into (4) the mixer/amp. I'm assuming the signal from the mic needs to be powered (although there is a little watch battery in it) - that's why I'm calling this an amp. I'm assuming there would have to be a AA or 9V battery in there.

> There is a dial (3) on the mixer/amp to change the relative mix between the two signals (or perhaps this is just changing the power of the mic signal). The remixed signal goes out to the headphones (5).

This is only my guess as to how it would work.

I'd be grateful if anyone would be willing to work through this project with me.

Thank you.

Eric Antonow

 

[mikeblas]

What you want to build is called a "mixer". If you search the web, I'm sure you can find some circuit ideas given that name. Or, get a book on opamps.

(I'm not giving a complete answer because I figure you want to explore and experiment for yourself. If not, let me know and I'll provide more details.)

 

[ericj]

Holy Crap, what a bad idea!

You can call it "Geeze, do i really sound like that?!" and it could put an end to sober karaoke overnight!

The drunken karaoke will continue on as usual.

On the other hand, there might be a way to mask peoples awful singing voices so that only people who aren't wearing headphones know how bad they sound.

 

[Clutz]

Quote:

Originally Posted by ericj Holy Crap, what a bad idea!

That's a little harsh, don't you think?

 

[antonow]

Holy Crap, what a bad idea! You can call it "Geeze, do i really sound like that?!"

Whatever horror you can possible imagine, I assure you (at least in my case) it's worse.

Still looking for some technical guidance on how to approach it. Maybe a specific question -- I'm assuming the mixer/amp needs to be powered and there's no way to simply splice the mic's signal with what's coming out of the player...

 

[ericj]

OK, my initial response was a bit on the, ahem, visceral side.

Knee-jerk reaction. Sorry about that. Didn't mean any offense.

What i meant to say was, most people who sing along with their favorite music do so mostly when there is both nobody around to hear them and they cannot hear themselves clearly.

This explains people singing in the shower, people singing with headphones on, and any time you've walked in on someone singing along with their stereo.

People are always surprised to hear what they sound like on tape the first few times. Even if it's good, but we all know it's usually bad. And it's never what you thought it would be - this is simply because of how humans are built. The vocal cords are close enough to the ears that it never sounds the same when you're hearing yourself while you talk as it does when you hear a recording.

As an occasional vocalist for a noise band, I know just how bad it can be. But since it's a noise band, we have the option of doing our mixing with the audio output turned off. We have in fact laid down one entire album without hearing any part of it. It's awful.

But i digress. The phenominon that allows people to enjoy singing without really hearing themselves is that they feel the vibrations of their own vocal cords, and it feels good. In a car or a shower, they can feel the reverberations of being in an enclosed space. It's a sensual experience.

Without some filtering and sweetening, what this would do is take something that works for people only because it's imperfect, and render it perfect.

Unless, I suppose, maybe your target audience is actual vocalists? My initial assumption was that it was intended as a recreational device - a sort of personal karaoke.

However, it might be pretty easy to filter and enhance their voice so it makes them sound like a superstar.

As for how to do it.

If you know nothing about electronics, it would be very wise to pick up a copy of Horowitz & Hill's "Art of Electronics".

I haven't checked, but there are likely examples of microphone bias, microphone preamp, and audio mixer circuits - and that's the bare bones of what you need to start with.

 

[Francis_Vaughan]

OK, I tend to agree on visceral side of things.

But in the interests of furthering the technical side, a few thoughts.

The headphone output of an iPod or clone, is low impedance, designed to power headphones. In order to mix in the microphone output you will need to do a few things.

Amplify the microphone input to roughly line level. This is because most microphones have a very feeble, and often quite high impedance output.

Mix the microphone (now line level) with the output of the iPod. This can be quite simply done if both signals are from low impedance sources (which they now will be.) A simple resistive mixer into an op-amp.

Now amplify the signal to headphone driver levels. This could easily be combined into the same stage that the mix resistors feed.

However, it will actually sound awful. The user's voice will appear in the middle of their head and, as described above, sound rather unnatural to the user. There is stuff that may help. Of course the standard answer to any person who actually can't sing is reverb

Using a couple of simple bucket brigade delays you may be able to create a mix of some reverb, and also a comb filter to make a pseudo stereo image that spreads the voice across the sound-stage. This might make for a much more palatable result. Some eq may be useful too.

But, if I ever find anyone within earshot, singing along with their iPod, with one of your inventions, I will come looking for you.

 

[DaKi][er]

Keeping it simple for starters, here's my idea of it
Could probably add some volume control on the Mic though

 

[mikeblas]

Quote:

Originally Posted by antonow Still looking for some technical guidance on how to approach it. Maybe a specific question -- I'm assuming the mixer/amp needs to be powered and there's no way to simply splice the mic's signal with what's coming out of the player...

Yep, the amp needs to be powered. Otherwise, it can't put out more than it got in and wouldn't be an amplifier.

You can integrate the microphone's signal with the output of the player directly using passive components, but it won't work well. The microphone has a tiny signal output compared the output of the MP3 player, and the player's signal will overwhelm the signal from the microphone.

 

[xluben]

Sounds like this could be modified into a DIY PTH module

You wouldn't even need a mixer, just a mic, switch and amp.

 

[antonow]

Thank you - this is exactly the kind of insight I was looking for. Is there any other detail you can provide on the type of delays/filters?

Oh, where I live and people already sing to themselves with their ipods on as they walk down the street. (I almost wrote 'walkman' which dates me). This 'invention' would only lower their volume level given that their voice would be mic'd.

-----
However, it will actually sound awful. The user's voice will appear in the middle of their head and, as described above, sound rather unnatural to the user. There is stuff that may help. Of course the standard answer to any person who actually can't sing is reverb

Using a couple of simple bucket brigade delays you may be able to create a mix of some reverb, and also a comb filter to make a pseudo stereo image that spreads the voice across the sound-stage. This might make for a much more palatable result. Some eq may be useful too.