Compressor/limiter

On a sunny day (Wed, 17 Feb 2021 07:21:48 -0800 (PST)) it happened mkr5000 wrote in :

In the long ago past I used the NE570 compander / expander chip. That chip was used in satellite transmissions and I used it in international phone lines (tx compand / rx expand). If you run Linux it can all be done in software with 'sox':

scroll down for explanation and sox parameters I used to emulate the NE570 compander in software with sox, no hardware needed.

Yes that circuit should work as advertised. Linear ICs like NE571 and SA575 are still made and used widely. For example see this datasheet:

piglet

Try THAT Corporation....

Used to design their stuff into compressors and AGCs the 1980s

Log amp to make the control voltage and VCA to control the gain.

They have a lot more parts nowadays and also have some app notes to help with the design.

Just what you're looking for !

boN

one person's "horribly inconsistent audio" is another person's "dynamics."

But there's a loudness standard for broadcast audio in the US including commercial streaming, ATSC A/85, question is if the "horribly inconsistent audio" is just due to peak vs. average levels or some channels you listen to aren't adhering to the standard, like I'm not sure that say YouTube automatically adjusts the audio on some random guy's video to comply.

In that sort of situation it could be hard to find set-and-forget peak limiting settings on an analog compressor that consistently sound good across channels.

The best way to make it sound like a 1965 AM radio would be to totally crush all dynamics out of it using a dedicated peak limiter like:

(turn the threshold all the way down and makeup gain all the way up)

Sum the channels into a low-power AM transmitter and tune it in on a

1965 AM radio

On second thought I'm not sure -13 dB on the threshold control will be enough to destroy the audio in the way the OP prefers

the horribly inconsistent audio, which is a trademark of digital audio any way. Soft one minute then an unreal blast the next. I'm a creature of the p ast and remember there were actually some linear chips strictly for audio c ompression and limiting but certainly none now. You guys are the design exp erts so looking for schematics or something you think would suffice. I want to get an hdmi audio extractor and put something on the analog audio and m ake it sound like a damn 1965 AM radio station !

prefered -- nothing fancy).

It'll work, but isn't ideal. Do you use a traditional audio amplifier, wi th tape monitor features? The easy circuit for this function drives a light bulb from amplifier outpu t, which drives a light-dependent-resistor to attenuate in the tape monitor path.

Other treatments, using a JFET, are commonly discussed.

ng the horribly inconsistent audio, which is a trademark of digital audio a nyway. Soft one minute then an unreal blast the next. I'm a creature of the past and remember there were actually some linear chips strictly for audio compression and limiting but certainly none now. You guys are the design e xperts so looking for schematics or something you think would suffice. I wa nt to get an hdmi audio extractor and put something on the analog audio and make it sound like a damn 1965 AM radio station !

s prefered -- nothing fancy).

th tape monitor features?

put, which

Sum the channels into a low-power AM transmitter and tune it in on a

1965 AM radio

lol -- won't go that far.

THAT stuff tends to be great. Only problem is IIRC you have to buy a tube

Look for a good sound card that contains audio FX. I had a E-Mu 0404 that let me control my audio level. My new MB only allows PCIe