dBx 3BX Three Band Dynamic Range Expander

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mediatechnology
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dBx 3BX Three Band Dynamic Range Expander

Post by mediatechnology »

Schematics for the dBx 3BX dynamic range expander. One of the first applications I saw using the non-linear capacitor.

Image
dBx 3BX Schematic

Large format: https://www.proaudiodesignforum.com/Images/jpg/3BX.JPG (4.4 MB)

When I had a 3BX I had thought about modifying it to be a feed-forward three band compressor. Check out the derived filters and FET switching inside the OA feedback loops as well.

Wayne

EDIT: 1979 patent for 3Bx showing the non-linear capacitor: https://proaudiodesignforum.com/images/ ... 177356.pdf
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Re: dBx 3BX Three Band Dynamic Range Expander

Post by emrr »

That looks a little bit crazy. Probably just that they put it all in one drawing! What era is this device?
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mediatechnology
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Re: dBx 3BX Three Band Dynamic Range Expander

Post by mediatechnology »

There is a second page I need to post with PSU and metering I had forgotten about.

It was early 1970's era.
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Re: dBx 3BX Three Band Dynamic Range Expander

Post by JR. »

Interesting the ancients are stealing our ideas again...

Those active cap multipliers with diode clamps to make it fast for large changes and slow for small changes is very similar to a circuit I did in the '80s for a NR... While I added a few other tricks too, it was the same general concept.

JR
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Re: dBx 3BX Three Band Dynamic Range Expander

Post by mediatechnology »

JR. wrote:Those active cap multipliers with diode clamps to make it fast for large changes and slow for small changes is very similar to a circuit I did in the '80s for a NR... While I added a few other tricks too, it was the same general concept.
Still found as the NLC in the Pico and THAT DN-114: http://www.thatcorp.com/datashts/dn114.pdf

Was yours in the NE570 compander we posted here?
JR. wrote:Interesting the ancients are stealing our ideas again...
On that note I'm tempted to start a thread on the "superbal" cirrca 1982.
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Re: dBx 3BX Three Band Dynamic Range Expander

Post by JR. »

viewtopic.php?f=6&t=252

here it is, a NE572 based tape NR

I did a bunch more than just the dual time constant C... I give a full description at the above link.



enjoy,

JR
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Re: dBx 3BX Three Band Dynamic Range Expander

Post by mediatechnology »

That's the one I remember. Very clever.
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Non Linear Capacitor in 1979 Patent 4177356

Post by mediatechnology »

1979 patent for 3Bx showing the non-linear capacitor: http://www.waynekirkwood.com/images/pdf ... 177356.pdf
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Re: dBx 3BX Three Band Dynamic Range Expander

Post by ricardo »

JR. wrote:viewtopic.php?f=6&t=252

here it is, a NE572 based tape NR

I did a bunch more than just the dual time constant C... I give a full description at the above link.
I grovel at your feet in awe, Oh Guru JR :o
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