walkman's mic-in jack not good for non-mic sources, why?

[chriscatfood]

i have a wm-sr10 sony walkman that has a built-in mic as well as a mic-in jack (that says "plug in power"). i've tried to use it to record from another source - from my preamp for the turntable and from my computer's audio out, with horrible results. the overall sound is very quiet and littered with noise. i know very little about audio in this sense, is it possible that the "plug in power" is the problem? is there anything i can do to get this input to record line-to-line audio decently?

 

[Arkay]

Just speculating here, but it seems to me that a microphone gives out a very weak, small signal. It needs to go through pre-amplification and then another round of amplification, to reach listening levels. The outputs from your computer or other gear give out a much higher-level, already partially amplified signal. You are probably over-driving the poor Walkman by pouring too much power into that input that is only designed to take the weak signal from a mic. Is there an "aux" input on it? That would be the one to use, instead of the "mic" in.


If you look on the back of many modern receivers and such, like HT gear, they will have "low-level outputs" and "high-level outputs", including the speaker out connectors. If the gear you are using has a "low-level output" or "direct out", try using that to feed into your Walkman, and see if it works better.

 

[koltrast]

Plug-in power is 'Sonyspeak' for phantom power. In professional use phantom power is a 48V dc supply which powers condenser microphones which otherwise would require an internal battery. Sony's Plug-in power does the same, although not 48V, so it's not interchangable.
Anyway, this has nothing to do with your problem.
Arkay is right. Pumping a line level signal into a mic input will overload the input. You need to use some kind of attenuator to step down the signal.

 

[chriscatfood]

thanks for the responses! my next question is, is there some kind of small, simple adapter to do this? ideally something i could take traveling in a backpack...

 

[x_25]

Plug it right into the line out on your computer and turn the volume (in the volume control panel) for everything as low as it can go but not quite off. (turn all the ones for wave and mp3 and such down and then turn the main one down as low as you can without turning it off.) This should bring the signal down low enough that it should be about even with a mic. Yes, I have done this and have had it work (although it was from a source into my computers mic in, but the same concept).

 

[koltrast]

Use a simple 'RCA line level attenuator'. Shouldn't be too hard to find. Use one which cuts the signal by 6db or preferably more. This should help. You need one for each channel of course!

 

[SaSi]

The Mic in inputs have a sensitivity of about 1~2mV (very similar to the Phono inputs in pre-amps). They tend to overload at about 80~100mV for the best equipment. I would expect portable devices to overload much lower.

The "low voltage outputs" from the amps (like Rec Out to tape) typically give 100~400mV, depending on audio level and any adjustments available.

One way to attenuate the signal is to build a resistor divider for the signal. In order to attenuate the signal enough to feed to the mic-in jack, about 10~20dB are needed. Take two resistors, 1kOhm and 48kOhm and solder/wrap then in line. Take the source signal and solder/wrap it at the end of the two resistor chain. Take an output signal from the ends of the 1kOhm resistor and feed that to the walkman.

What you would be doing is dividing the input signal between a large and a small resistor. The large resistor will take most of the voltage drop and the small one will take a small voltage drop. The two ends of the small resistor will give you an attenuated signal.

Any value resistors will do, provided they are not smaller than 1~2kOhm for the smaller. The larger the better, so that the source isn't overdriven by current.

 

[philcib]

Plug-in power is 'Sonyspeak' for phantom power. In professional use phantom power is a 48V dc supply which powers condenser microphones which otherwise would require an internal battery. Sony's Plug-in power does the same, although not 48V, so it's not interchangable.
Anyway, this has nothing to do with your problem.
Arkay is right. Pumping a line level signal into a mic input will overload the input. You need to use some kind of attenuator to step down the signal.

Actually Phantom power is for BALANCED mic signals. Plug in power is for
UNBALANCED mic signals. The two are not the same thing.

 

[koltrast]

What I meant was that the principle is the same. The microphone gets it's power from the unit it is plugged into.