Noise Reduction
SSM2000
I didn't even know that the CBS process existed, I remember HighCom and dbx and Dolby very well.
In the late 1990s, I experimented with the HUSH system, which also produced amazing results. But now the CX system makes me very curious.
How does it work and what does it do with non-CX encoded LPs?
Great
SSM2000
I didn't even know that the CBS process existed, I remember HighCom and dbx and Dolby very well.
In the late 1990s, I experimented with the HUSH system, which also produced amazing results. But now the CX system makes me very curious.
How does it work and what does it do with non-CX encoded LPs?
Great
How does it work?
To the technical aspects, I recommend reading the Elektor edition mentioned above; or whatever else you can find about it on the internet.
If you don't have the Elektor edition, I can email the relevant article pages and whatever other reading material I have. (*.zip file)
I already wrote something about the listening impression in the first post
and also on my own site (german): http://suzuki-gt250.de/misc.electronics/AUDIO/CX-Decoder/CX_Decoder.php
The whole thing works by increasing or decreasing the level, so nothing is actually being encoded or decoded in the actual sense.
E.g.: Very quiet passages of the sound material are cut onto the record at an increased level (+20db) in order to be significantly above the background noise level of the record, and when played, these passages (including noises) are played back by the “decoder” at a correspondingly decreased level.
The background noise therefore disappears with quiet pieces of music or even when there is no sound signal.
Also the two adjusters on the decoder are nothing but level controls.
If you play CX records without a decoder or non-CX records with a decoder, you will experience sudden, seemingly unmotivated level jumps depending on the piece of music/sound material.
With some rock music, which genuinely consists of constant (high) volume, you don't notice anything, in contrast to, for example, classical music, where there are larger differences in volume in the sound material.
(By the way, I have one leftover board for the CX decoder as shown above, also the IC HA12044.
If someone would be interested..... )
To the technical aspects, I recommend reading the Elektor edition mentioned above; or whatever else you can find about it on the internet.
If you don't have the Elektor edition, I can email the relevant article pages and whatever other reading material I have. (*.zip file)
I already wrote something about the listening impression in the first post
and also on my own site (german): http://suzuki-gt250.de/misc.electronics/AUDIO/CX-Decoder/CX_Decoder.php
The whole thing works by increasing or decreasing the level, so nothing is actually being encoded or decoded in the actual sense.
E.g.: Very quiet passages of the sound material are cut onto the record at an increased level (+20db) in order to be significantly above the background noise level of the record, and when played, these passages (including noises) are played back by the “decoder” at a correspondingly decreased level.
The background noise therefore disappears with quiet pieces of music or even when there is no sound signal.
Also the two adjusters on the decoder are nothing but level controls.
If you play CX records without a decoder or non-CX records with a decoder, you will experience sudden, seemingly unmotivated level jumps depending on the piece of music/sound material.
With some rock music, which genuinely consists of constant (high) volume, you don't notice anything, in contrast to, for example, classical music, where there are larger differences in volume in the sound material.
(By the way, I have one leftover board for the CX decoder as shown above, also the IC HA12044.
If someone would be interested..... )
This is a very interesting thread, despite its age. I experimented with many compander schemes back in the late 80s to help breath life into poorly encoded Dolby recordings.
The radio station I worked for at the time in southern Germany broadcast alot of classical music. They put a lot of effort into lowering the noise floor of their audio.
They used a proprietary compander system developed by their own engineer, which was similar to DBX, but it had a much wider effective range across a greater FR. With a decent tuner, you could achieve over 70 dB of effective dynamic range which rivaled decent vinyl. I had to calibrate this system with a test tape every morning, which had to be done in under 5 minutes.
The system essentially was made up from several VCAs groups which had linearity adjustments across the range of 40hz - 17khz split into 8 frequency bands and 5 level ranges per band, totalling 40 bands. There also was a very sharp multiplex trap that had to be set within 20ppm.
For my own purposes back in the early 90s, I designed a custom expander circuit with Dolby B and C ICs commonly used in tape decks. It had a level and threshold adjustment per channel. The system could be switched between Dolby B or C with dedicated adjustments for either system.
There are some provisions in Steinberg's Wavelab software for expansion of pre-compressed audio which work very well for cleaning up Dolby B recordings. This allows you to clean up old tape transfers. Dolby C and DBX are much more finicky as is Dolby A.
The radio station I worked for at the time in southern Germany broadcast alot of classical music. They put a lot of effort into lowering the noise floor of their audio.
They used a proprietary compander system developed by their own engineer, which was similar to DBX, but it had a much wider effective range across a greater FR. With a decent tuner, you could achieve over 70 dB of effective dynamic range which rivaled decent vinyl. I had to calibrate this system with a test tape every morning, which had to be done in under 5 minutes.
The system essentially was made up from several VCAs groups which had linearity adjustments across the range of 40hz - 17khz split into 8 frequency bands and 5 level ranges per band, totalling 40 bands. There also was a very sharp multiplex trap that had to be set within 20ppm.
For my own purposes back in the early 90s, I designed a custom expander circuit with Dolby B and C ICs commonly used in tape decks. It had a level and threshold adjustment per channel. The system could be switched between Dolby B or C with dedicated adjustments for either system.
There are some provisions in Steinberg's Wavelab software for expansion of pre-compressed audio which work very well for cleaning up Dolby B recordings. This allows you to clean up old tape transfers. Dolby C and DBX are much more finicky as is Dolby A.