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Thread: Will digital voice recorders work to load/save data for old computers with a cassette

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    Default Will digital voice recorders work to load/save data for old computers with a cassette

    Will digital voice recorders work to load/save data for old computers with a cassette interface?

  2. #2

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    Probably depends on the particular computer, and especially if it relies on the motor-control signals that later cassette records included for answering machines and the like. But on a basic audio level, yeah, probably; effective bandwidth on compact cassette is something like 12-15 KHz, and any decent digital audio device can far outperform that. Though I would be curious what MP3 compression does to data signals; might want to use a FLAC recorder.
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    If the recorder can do AIFF/WAV/whatever-uncompressed-format it'll probably do fine as long as it supports a decent bitrate. (See projects like the Apple II Disk Server; it works fine through a standard smartphone's audio out.) Compression will probably torpedo things.

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    I was messing around with capturing and replaying cassette data on a 5150 motherboard a few months back, and I found the bigger problem was not recording it, but playing it back. Some computer audio systems try to filter out "noise", and most cassette data signals basically are "noise". Over all, if one can adjust the "bass" and "treble", it will work. But I noticed that some computers don't allow the user to adjust those (but have a zillion other fancy useless settings).

  5. #5
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    Quote Originally Posted by SomeGuy View Post
    Some computer audio systems try to filter out "noise", and most cassette data signals basically are "noise". Over all, if one can adjust the "bass" and "treble", it will work. But I noticed that some computers don't allow the user to adjust those (but have a zillion other fancy useless settings).
    Re: that "Apple II Disk Server" I mentioned, for me it works fine through my mobile phone and a cheap*** old Android tablet, but I've had much worse luck trying to use an Apple MacBook. (And not just with the Apple II, I had issues, again with the MacBook, trying to play cassette audio into a Tandy Color Computer.) So magical filtering or equalization or whatever may indeed be an issue.

  6. #6

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    I picked up a Sony icd-px370 at best buy after making them price match it to amazon. So far results are similar to SomeGuy's experience. I disabled anything in the settings that alter the sound like "clear voice" and other features. I sent the input to microphone on medium sensitivity and it has a bar graph showing signal strength that seems to put it in the center at this setting. The problem is loading. Most of the time it works, but not all the time. The volume goes up to 30 and it seems to have the best results in the 25-30 area, it fails more quickly at 20 and under. Not sure I love it. Maybe I need one that can record in WAV as an option.

  7. #7

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    Ok - a follow up. I measured the output of the tape deck on my oscilloscope and used that to get the digital voice recorder outputting similar. It turns out that it needs the external input set to microphone/medium sensitivity. Once this is done, set the volume to maximum (30) and it outputs a signal very close to where the tape deck was (800mV peak to peak) that worked well. I ended up switching to the highest recording mode MP3 192K because the mono 48K looked rougher and I had some load failures trying to load with it. So far though the 192K settings seems to be working great.

  8. #8

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    Just as another data point -- I'm using a Sony ICD-PX470 (in MP3 mode) to successfully record and playback TRS-80 Model 1 compatible cassette audio. This is on a modern clone of the original hardware, which uses a copy of the original output circuit. The input circuit is somewhat modified though, as it's a variant of an input signal conditioner I had/have on my original box. I've also verified with a scope that the audio input signal from the digital recorder is pretty close to what I get out of the original cassette player (although it is missing the (quite large) 60Hz "carrier" that I see from the original).

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