SOLIPSIUMAlpha

SOLIPSIUM Super resolution audio engine

Cassette tapes

Clean up a cassette or answering machine tape after you capture it.

Capture the tape to a file and drop the file here. Solipsium measures its hum, hiss, clipping and gaps before it changes anything, and names what it found.

Drop a captured tape here

Solipsium checks it in your browser for clipping, hum and noise, without uploading it. It can then repair the first 20 seconds for you to hear, with no account.

WAV, FLAC, MP3, M4A and more, up to five minutes for the check.

Choose a captured tape

Capturing

Make a file from the tape.

Play the tape on a deck connected to the computer, and record it with the recording program you already use.

  1. Connect the deck.

    Run the deck's line out into the computer's line in, or plug in a USB cassette deck.

  2. Set the level on the loudest passage.

    Play the loudest part of the tape and set the recording level so it stays under full scale. A capture that reaches full scale clips, and clipped peaks can only be partly raised back.

  3. Save it as a WAV.

    A WAV keeps every sample the deck sent. The first question below gives the settings.

If the computer lists the deck as an input, the online voice recorder can capture up to 30 minutes at a time in the browser, as a mono 16-bit WAV, with echo cancellation, noise suppression and automatic gain asked off.

Fault by fault

What a tape brings, and what is repaired.

The check in your browser names mains hum, background noise, clipping, dropouts and muffled sound, and says when it hears each one. The try repairs the first 20 seconds on Solipsium's server and lists a reason for each step. Solipsium's free try is built for speech.

Hum from the deck.

Hum is labelled when the lines at 50 or 60 Hz and its multiples stand 10 dB over the frequencies around them. It is notched out in bands 3 Hz wide: the first four harmonics always, and higher ones up to the 24th where they stand 8 dB over their neighbours. The result reads: “Mains hum was found, so it is notched out before any cleanup.” Hum that comes and goes, in stretches of 3 seconds or more, is notched only where it is, with quarter-second fades: “Mains hum was found in parts of the recording, so it is notched out there; the voice is put back wherever the notches removed nothing.”

Hiss.

Hiss that holds steady within 26 dB of the voice gets Full-band speech cleanup: “A steady noise floor was found, so it is removed.” When held musical tones sit under the hiss, cleanup stays gentle and lowers it by at most 6 dB. Lighter hiss, more than 26 dB under the voice, is not labelled; when nothing else is found, a listening model decides whether speech cleanup runs. On an answering machine tape whose sound stops under about 5.4 kHz, as a phone line does, hiss gets gentle cleanup, and only together with the treble rebuild.

Clipped peaks.

Flat tops up to 10 ms long, from a capture set too hot, are partly raised back from the undamaged samples around them, never more than 2.3 dB over the clip level. A top that is unsafe to raise is left exactly as it was.

Dropouts.

A tape dropout is a dip in level, and the gap filler leaves it. A hole of exact digital silence up to 100 ms, from a glitch in the capture, is filled by continuing the voice's pitch from each side: “Short holes of lost audio were found, so they are filled from nearby sound.”

Dull treble.

An answering machine message came down a phone line. When its sound stops under about 5.4 kHz and nothing else was found, the AP-BWE model rebuilds the treble and keeps the sound below 4 kHz as it was: “Little sound was found above 4 kHz, like a phone line. The treble is rebuilt from the sound below it, which is kept as it was. What is added is inferred.” With steady noise as well, gentle cleanup runs first, then the rebuild. A tape whose sound stops between 5.4 and 8.3 kHz gets no rebuild.

Wow, flutter and print-through are not repaired.

Questions

About tape transfers.

What should I capture the tape to?

A 16-bit WAV at 44.1 or 48 kHz. If it has to be an MP3, use 192 kbps or more, since a lower bitrate cuts more of the treble the tape still has. Solipsium's server decodes every file at 48 kHz.

Will it remove tape hiss?

Hiss loud enough to be labelled gets Full-band speech cleanup. The editor describes that cleanup as: “Targets hiss in speech. Check quiet or distant voices; may remove music and ambience.” Compare Original and Repaired on the same words before you keep it.

The tape drops out in places. Can that be filled?

A dip in level from worn tape is left as it is. A hole of exact silence up to 100 ms is filled, and the fill is labelled an estimate. If the silence came from a glitch in the capture, capturing that stretch again gives you the real sound.

Where does hum from the deck come from?

Hum on a capture can come from the deck's power supply or from a ground loop between the deck and the computer. Plugging both into the same outlet, or running a laptop on its battery, can break a ground loop before you capture. Hum already in the file is notched as the hum tile above describes, including hum that comes and goes.

Can it bring back the treble a tape lost?

In two cases: a phone-line recording, as above, and a tape whose sound stops between about 8.3 and 11 kHz, which looks like a file saved at 16 kHz and gets AP-BWE's 16 kHz model. That result reads: “The recording seems to have been saved at 16 kHz, so nothing is left above 8 kHz. The treble is rebuilt from the sound below it, which is kept as it was. What is added is inferred.” Either rebuild runs only when nothing else was found, or only steady noise. In the editor, a free account can run AudioSR on a passage of up to 60 seconds, and what it adds is inferred.

What about a whole box of tapes?

The family recordings page covers voicemails, memos and old tapes. A shop or an archive that transfers tapes can read about the pilots on Solipsium for teams.

Is my recording uploaded?

Not for the check, which runs in your browser. Pressing Repair the first 20 seconds sends those 20 seconds; when your browser could not open the file, or it runs over five minutes, the file itself goes to Solipsium's server, so the try is offered for it only up to 25 MB. Solipsium keeps only the first 20 seconds and deletes them within an hour. If you are signed in, a file you drop or choose is uploaded to your account and opens in the editor instead. The privacy notice has the rest.

Free audio tools

Related free tools.

For one fault at a time, or a capture too long to check in one go.

The whole tape.

Make a free account and drop the same capture into the editor to repair all of it, up to 30 minutes at a time.

Repair the whole tape

Free account, no card.