Help: Calibrating Tape Restore Live!: Dolby B volume calibration
This step is only necessary if you will be using the Dolby B removing filter of Tape Restore Live!
When using Dolby B, it is essential that the sound that is read from the tape matches the recording volume as closely as possible.
This is the main reason why tapes recorded with Dolby B often sound dull
when played back on another cassette deck, and why tape wear affects recordings with Dolby B much more
than recordings without Dolby B. Often, old Dolby B recordings are played back with Dolby turned off to get an acceptable
sound. Tape Restore Live! can fix these old recordings, but the Dolby B in software needs to be calibrated
against the Dolby B on the original recording.
This section describes how to calibrate Tape Restore Live! to match the Dolby B encoder of your cassette deck, and the PC
recording volume settings.
When calibrating Tape Restore Live!, it is essential to approach the
real recording and sampling situation as closely as possible. This means
that, if possible, the tape deck on which the original recording was made
should be used to record calibration sounds, and the tape deck that will
be used to digitize the recordings should be used to play it back.
The recording volume on the PC must be identical to the recording volume
used to sample the actual recordings.
If the original cassette deck is no longer available, see the hints below
for some tips on performing this calibration manually.
Important: The PC recording volume must match the recording volume of the
tapes that will be restored. So first find a tape with a loud recording, and use that first to find the
optimal PC recording volume. Perform this step afterwards.
To calibrate Tape Restore Live!, perform the following steps:
Record the sound 'dsp_tape_restore_live - Calibrate Dolby B volume.mp3' on the
cassette deck on which the original recording was made, with Dolby B turned on.
This file can be found in the Winamp plugins directory,
usually 'C:\Program Files\Winamp\Plugins'.
Play the tape back on the recorder that you will be using to digitize the recording that you want
to restore, with Dolby is turned off.
Record it on the PC, with the same volume that is used for the recordings that will be repaired.
Hint: Record the sound 'dsp_tape_restore_live - Manual tape head calibration helper sound.mp3'
just before the calibration tone, and use it during playback to calibrate the
tape head.
Open the recording in Winamp.
Enable Tape Restore Live!, turn the Tape Bias and Dolby B remover filter on.
Also enable 'Display 2kHz tone volume'.
Play back the recording, and play with the 'PC recording volume' slider, until the
2kHz tone volume display is as flat as possible.
Peaks mean that the 'PC recording volume' slider is set too high,
valleys mean that it is set too low.
Peaks: PC recording volume is set too high.
Valleys: PC recording volume is set too low.
Flat: PC recording volume is set correctly.
IMPORTANT: Please ignore steep peaks or valleys like this one.
Dolby B is now calibrated. Make sure that you keep the recording volume
equal for every tape that you convert to the PC.
If the original tape deck is no longer available,
you can try to calibrate it using another cassette deck. The differences
might be small enough. Otherwise, try the following steps:
Find a Dolby B recording of a song that was made on the old cassette
deck, where the song fades away slowly (which is often the case with
older music).
Turn on 'Constant volume'. Now all sounds are played back with the same
volume, regardless of the recording volume.
Play it back and play with the 'PC recording volume' slider.
If the
slider is set too low, lower volume recordings will sound sharper
(too much high frequency sounds)
than the higher volume recordings. If this is the case, turn the slider
up.
If the
slider is set too low, lower volume recordings will sound less sharp
(missing high frequency sounds)
than the higher volume recordings. If this is the case, turn the slider
down.
Keep doing this until all the sounds are equal, regardless of the
recording volume.
Note: Because Winamp uses a buffer, it takes a few seconds before
the effect of changing the slider setting can be heard.
Dolby B is now calibrated. Make sure that you keep the recording volume
equal for every tape that you convert to the PC.
Peaks: PC recording volume is set too high.
Valleys: PC recording volume is set too low.
Flat: PC recording volume is set correctly.
IMPORTANT: Please ignore steep peaks or valleys like this one.