Why does a tape recorder plugged into my computer's Mic input record so quietly?
February 23, 2012 7:33 PM   Subscribe

Why does a tape recorder plugged into my computer's Mic input record so quietly?

I have recordings of my grandfather talking about WWII on a tape recorder, and want to digitize them to MP3 and eventually transcribe them. The tapes are those small voice recorder sized tapes, with a 2.5 inch jack ear piece out. I have a 2.5 inch to 3.5 in converter cable, and have plugged this into both my computer's mic in and line in inputs.

The result, when trying to record the audio in both audacity and adobe audition, is way to quiet to be usable. It's picking up a signal, but it's around -45 db, and when you try to increase the volume, the hiss pretty much drowns it out.

I thought it may have been an issue with my computer, but just plugged it into the mic in on my wife's computer and audacity had the same issue.

Any ideas how to fix this? The next thing I was going to try is just mic-ing the tape recorder while it is playing out loud, but obviously this would degrade the quality as well.
posted by JoeGoblin to Technology (10 answers total) 3 users marked this as a favorite
In whatever OS you're using, have you gone to your audio properties and checked the recording level on the line-in?
posted by brownrd at 7:43 PM on February 23, 2012

You don't want to use the mic in, most likely, but a line in if it has one. Increase the volume on the tape player as much as possible - you want to be hitting more like -3db.

(I assume you mean 2.5mm and 3.5mm not inch)

When you are increasing the volume in audacity, are you increasing the *input* volume or your speaker's volume? You want to increase the input volume (some, but doing it too much will not help if the source is too quiet)

If you absolutely can't get the tape player's output high enough (make sure there's not like a boost switch or something, some tape players have one) then you probably are going to want to try a pre-amp of some kind. Or, you might just try a reasonably decent external sound device - there are some pretty nice USB sound devices that have good inputs with input volume controls, monitoring, etc. Most of the M-audio ones are OK, I've used them for years for low-demand audio recording.
posted by RustyBrooks at 7:44 PM on February 23, 2012

Is that converter cable stereo or mono?
posted by Ardiril at 7:46 PM on February 23, 2012

If you're using a PC, look for a light blue jack. That's the Line In jack. If it's not on the front, check the back. Plug into that.
posted by Sys Rq at 8:05 PM on February 23, 2012

Response by poster: I'm in Windows 7. The Recording Level on the Line in is set at 100.

Tape player is up to 100% as well. When you don't have anything plugged into it's mic out, and it plays through its own speaker, it's quite loud.

(Yes, 2.5mm).

The converter cable is a simple male 2.5 to female 3.5. I'm not sure if it's mono or stereo or if the tape recorder is even in stereo in the first place.

Audition is apturing audio at around -45. Frustrating.
posted by JoeGoblin at 8:07 PM on February 23, 2012

There is a definite difference between the performance of the line in and mic jacks, so if you're in once, switch to the other and see what happens.

Also, there used to be a checkbox somewhere for microphone boost, but I can't find it on my XP machine, so that may have gone away with Windows 2000, or it might be buried in your chipset software.
posted by Kid Charlemagne at 8:38 PM on February 23, 2012

You may have to experiment to see what works - the line in method suggested by RustyBrooks "should" give the best results though I would caution against going too high - one you clip a digital signal it degrades drastically, and if you set your recording software to 24bit and record wavs first you can afford to peak around -12dB, and still have plenty of headroom to apply noise reduction and any other post processing to clean up the recording later. Once you have a good digital copy you can dither down to 16bit and export to mp3 (or better still ogg vorbis / aac or FLAC). Perhaps the recordings would be of archival interest to others after your transcribing?

Anyway, aside from my getting distracted with technicalities, you may find that taping an external mic to the speaker and trying different volume settings gives an acceptable recording if you have a quiet enough room - preferably with lots of soft furnishings (don't be afraid to borrow some cushions or a blanket to help isolate you recording area and reduce room noise if do it this way.

The recorder is probably mono, so you'd only get signal on the left channel when connecting stereo equipment - if you have a small pair of powered computer speakers try plugging those in via your 2.5mm adaptor and see if what you get - it could be that the jack socket is dirty / poor quality.

Good luck.
posted by dirm at 8:41 PM on February 23, 2012

nthing the need to use the line in jack, not the mic jack, although it sounds like you may have tried both. In which case I'd second the suggestion above re: pre-amp devices to boost the signal from the tape recorder.
posted by NikitaNikita at 8:52 PM on February 23, 2012

When you don't have anything plugged into it's mic out

You originally said you were using the jack for an ear piece out, so I'll assume that's what you mean rather than "mic out" (connecting the mic input on the tape player to the mic input on the computer is clearly not going to work). I'll also assume that when you say "ear piece" you're talking about one of those older types that fits in just one ear; that would be pretty typical for an old voice recorder using microcassettes, which is pretty unlikely to be a stereo device.

If I'm right, that means that the jack in the recorder is almost certainly mono, not stereo. If you have the actual earpiece, look at its 2.5mm plug to confirm this: if it's a mono plug the connector will be a tip+sleeve type; stereo plugs are tip+ring+sleeve.

Most PC microphone inputs are mono, even though PC microphones come with tip+ring+sleeve plugs. Tip is signal, sleeve is signal ground, and ring is a current-limited microphone power supply. Microphone inputs will usually be expecting quite a lot less signal than you'd get from a typical headphone or line output; for connecting a tape recorder it's much better to use line-in.

A standard PC audio cable has two signal conductors connecting tip to tip and ring to ring, and a shield conductor connecting sleeve to sleeve. These are also the connections you'd find in a stereo 2.5mm to 3.5mm adapter. Looking at the 2.5mm plug on your adapter should tell you whether it's mono (tip+sleeve only) or stereo (tip+ring+sleeve).

When you plug a tip+ring+sleeve plug into a tip+sleeve socket, the tip will connect as intended but what happens to the ring and sleeve depends on the particular socket. You can get (a) sleeve connected properly, ring disconnected; (b) plug ring and sleeve shorted together and connected to socket sleeve; or (c) plug ring connected to socket sleeve, plug sleeve disconnected. If (c), you will get signal arriving at the PC without a reference ground and this will make it very weak and very noisy.

The correct solution is to use a 2.5mm mono to 3.5mm stereo adapter, which will connect the 2.5mm tip to both tip and ring on the 3.5mm side, and wire that to your PC's line in socket with a standard PC audio cable.
posted by flabdablet at 9:22 PM on February 23, 2012 [2 favorites]

It's unlikely, but you may be in a situation where your computer has a balanced input, and you are giving it a mono signal over a stereo cable, which would cause the sound to cancel itself out.

Try this: Do what you have been doing, but unplug the cable going into your computer a little bit at a time. If you have a problem with a balanced input, as soon as one of the conductors comes undone in the plug, the signal should jump way up. If unplugging the cord part way doesn't change anything, than it is a different issue, but without being there, I wouldn't be able to figure it out.
posted by markblasco at 10:12 PM on February 23, 2012

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