How to monitor microphone sound through headphones?

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clay1st

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Hi,

My dilemma is very simple, I wish to listen to live sound from a basic 3.5mm output microphone using 3.5mm input headphones/speakers.

There obviously needs to be some kind of intermediary amplification - but what piece of kit would best do the job?

It needs to be battery operated, small, and cheap! :thumbs up:

Thanks! Clay

mic to headphones.webp
 
Well, if you have a laptop, that would qualify on all counts, depending on how big it is and what you mean by "small."

One significant question is whether the mic requires power. If it does, that complicates things. An appropriate higher-end video camera would work, but that's not exactly cheap unless you already own it. If the mic requires power of the sort ordinarily supplied by a video camera, you're probably only going to find that in a video camera or an outboard portable preamp that's intended for serious video people who want a step up in audio performance from their camera (read: expensive).

Some MP3 players have mic input jackes. Many standalone SD-card recorders do too. You can even connect both a mic and headphones to an iPhone (I think) with an 1/8" insert cable (one TRS plug splitting into two TS jacks).

There are some battery-powered mic preamps with headphone monitoring, though - as mentioned - they tend to be more high-end, and thus pricier, than what you probably want. The Sound Design MM1, for example. Semi-ironically, it probably winds up being cheaper to use something that does other stuff (like recording) and also has a mic preamp bulit-in, than a standalone preamp.

Some choices would require you to use an adapter, e.g. to plug the mic into an XLR jack, or the headphones into a 1/4" jack. Neither - particularly the latter - is enormously difficult.
 
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Another thought: mini-cassette recorder with a mic jack. I don't know where you'd find one, exactly. Goodwill, maybe?
 
Just to be confusing, and answer for the third time:

I didn't look at the photo initially. Based on that - particularly the TRS jack on the mic and the fact it's a shotgun design - I suspect that mic requires video-cam power. You can get that from (i) an appropriate camera, obviously, (ii) a preamp intended for videography, which may cost more than a cheaper camera or (iii) cleverly wiring up a batter-power supply yourself.
 
I am actually designing an electric stethoscope. (I have made a bell-diaphragm with flared tubing to slip a microphone into)

I have made a prototype using a voice recorder as the intermediary between microphone & headphones - but it doesn't do live output, you have to record first, then listen.

Clarifications:

Power? - This is not powered mic, and besides it is interchangeable with several others I have - including XLR mics if needed...

laptops/videocameras/cassette players? - These are all a bit too bulky for my project, unless someone could suggest how to extract the active part of a cassette player that I actually need?

MM1 - Yes, I came across the 'Sound Devices' MM1 & MP1 and they seem the kind of thing I need.... except they cost ~£400.... I think they're intended for TV studio use.

Spy devices - That's actually a really good idea, but they all seem to have built in microphones that seem like they wont fit into my stethoscope tubing....


Thanks for the ideas so far guys!!:)
 
Yeah... I could just buy one, I know they already exist... I just figured since I have lots of spare headphones, microphones & stethoscopes I could make my own... I only need one part...
 
Fiio?: Sadly headphone amplifiers don't fit the bill, I own a FiiO E3 and a powered Behringer headphone amp... I get zero output when I use either in the loop. Strange, because they should provide enough gain in theory...

Spy ear circuit: It's a neat idea, I'd be willing to try it. It might be easier to buy a cheap hearing amplifier/spy ear with a built in microphone then hack it to attach my own microphone instead!

Any suggestions on how to do that would also be great!... I feel that might require a separate thread/some more research though.
 
Let's step back to basics here for a moment.

The electrical output of microphones is extremely low...typically -50 to -60dB. Any electronic device using a microphone has what is known as a micophone pre amp as the very first stage when you plug in the mic. The mic pre amp raises the low microphone signal to somewhere around 0dB (known as line level) which is what electronic devices work with internally. Then, the output you plug your headphones into is amplified again to drive the headphones.

The suggestions to use something like an old mini cassette recorder are good ones because they have the gubbins you need built inside. You're going to have problems finding something cheap that does just what you want because it's rare in the the extreme to want to simply listen to a microphone. Normally people want to record it or mix it or something.

An additional issue is that I agree the mic you picture looks like an electret designed for use on a video camera. These often DO require a small amount of voltage (provided by the camera) to work. If you know for sure this one doesn't, great, but...

Now, my suggestion. You mention that you have a variety of other mics available to try, including XLR ones. If so, move to XLR since you'll have a lot more flexibility in terms of gear to hook them to. Then, for the XLR mic scour eBay for the cheapest, nastiest Behringer mini mixer you can find. The start around $60 new so I'd hope you can find a used one for well under $30. This'll give you something you can plug an XLR mic into, a mic pre amp and a headphone amp, then a socket for a headphone.

Finally, at the risk of being a downer, when my wife was pregnant with our last baby, I tried to rig something like this up using really good gear. I never got it to work as well as a $4 midwife's ear trumpet.
 
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