I just used CoolEdit to open an mp3 I made from an old audio tape, and saw this: [img]413b6b5206[/img]

I only see it on files I pulled in from audio tape - is this an inherent problem of ripping from audio tape, or did I screw something up?

I saw something similar once on an mp3 encoded from the radio. But the line was 1 khz higher and there was something that looked like a filter around 15 khz. Later I read somewhere that FM radio uses a "stereo pilot" at 19 khz. Something that tells the radio that it has a stereo signal i guess. Maybe tape recorders use a similar system? Just speculation tho...

Can't remember well right now, but it could be the polarization or bias signal used at magnetic recording.

Or it could be interference in the line from a component of your computer or something around it.

So, do you think I should lowpass just below the signal (say at 17kHz)? Given the age of the tapes I'm ripping, I'm guessing there isn't meaningful content above there anyway.

Yeah. Probably a good idea anyway. --alt-preset 128 may actually be a good setting to encode tape rips like this with...

Try it, see if it loses anything in the translation. Pretty simple formula, if you don' t know then give it a try...

I think that the tape bias is far outside the audible range. This could be an FM 19 kHz tone, but it would mean that the tape is running 5% too slow, that's a bit too slow
Mine runs 3% too slow, and it's quite annoying.

And who will tell me what's this 30 kHz tone in the background noise of my phono input ?

[img]a275372978[/img]

BTW, my computer screen is at 81.5 kHz

I just checked my original WAV files, and they don't exhibit the "noise" at 18kHz. They were encoded with standard using Lame 3.90 (not sure which rev). When I re-encoded one of the WAVs, it didn't exhibit the same problem - it looked normal.

AFAIK the tape bias or pilot (or whats-its-English-name) is located at 30KHz for MC Cassette - so may it be studio tape bias from the master-tape ???

No, I wasn't playing anything, the turntable was not even plugged. It is a recording of the bare plug.