Pro Audio Design Forum

The FCS products; one of our hosts here.

Oh, I couldn't google anything about them.

I thought it was something you built yourself.

The FCS comps are an evolution and refinement of the basic THAT app notes, so an applicable reference.

Their real name is Foote Control Systems, and they seem to do compressors, not limiters. Is that so?

An adjustable compressor can be used like a limiter, but not the other way around.

JR

Limiting is question of ratio, no? They do high enough ratio, and the non-linear circuit gives acceptably fast response. In my example, I used them as limiters. I can flatline transient rich program material with this sort of THAT based compressor if I really want to, with the non-linear side chain timing also providing some AGC characteristics on sustained peaks. I've found a simple (and probably faster) small peak detector capacitor side chain will suffer from more obvious release artifacts, and doesn't work as well in practice.

Almost nothing I've ever heard will give you an acceptable sounding brick wall infinite ratio limiter in the analog domain, with a diode clipper usually sounding as good as anything else in that realm.

Anyway, don't get hung up on the FCS in particular, it's just an example of a THAT based unit that functions along the lines implied by THAT app notes. Dig into the notes and try some things.

emrr wrote:Limiting is question of ratio, no? They do high enough ratio, and the non-linear circuit gives acceptably fast response. In my example, I used them as limiters. I can flatline transient rich program material with this sort of THAT based compressor if I really want to, with the non-linear side chain timing also providing some AGC characteristics on sustained peaks. I've found a simple (and probably faster) small peak detector capacitor side chain will suffer from more obvious release artifacts, and doesn't work as well in practice.

As I think I've already said generally limiters are high ratio, fast attack and fast release.

A great deal of work has gone into optimizing a few specific limiter applications. One is for broadcast to prevent over modulation at the transmitter. Orban was pretty respected for his work in transparent limiting, while broadcasters morphed into applying heavy compression for loudness wars.

A slightly more pure limiting application is for clip limiters associated with power amps. In that specialized case they detect clipping and use that to drive a fast gain reduction with similarly quick recovery after the transient. Most customers do not realize it is limiting unless they look at the clip limiter lights.

Almost nothing I've ever heard will give you an acceptable sounding brick wall infinite ratio limiter in the analog domain, with a diode clipper usually sounding as good as anything else in that realm.

It is impossible to make a dynamic processor analog or digital without creating some kind of artifact. In fact the audio signal gets multiplied by the gain reduction step function. The impact can be mitigated by different techniques but you can not alter the sound without altering it...

Anyway, don't get hung up on the FCS in particular, it's just an example of a THAT based unit that functions along the lines implied by THAT app notes. Dig into the notes and try some things.

Yup the THAT chip set is an excellent collection of basic parts and if anything the hard part is reading all the application notes and figuring out what yiu don't need.

JR

I can't find that re-design article for the THAT 1510, where it was mentioned why to use the 1N4004GP instead of regular 1N4004.

Is it really important or the difference will be minor?

The GP types do not seem to come in SMD version.