Limiters with optocouplers

Where we discuss new analog design ideas for Pro Audio and modern spins on vintage ones.
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JR.
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Re: Limiters with optocouplers

Post by JR. » Sun Mar 08, 2015 2:06 pm

If you are proud of your woofers and amps, here's a track to listen to. And don't crank it up until you are confident you system can keep up. :oops:

http://www.danleysoundlabs.com/danley/w ... inale4.zip

He only claims 70 dB dynamic range but I trust him that it's a solid 70... Lots of info in the
20Hz region with decent stuff down to 10Hz... not exactly music (A fireworks show recorded from a 1/2 mile away)
but classical music has used cannons, artillery, and mortars to punctuate symphonic music for a long time.

Tom Danley hasn't shared exactly how he made this recording, but I'll bet dollars to donuts that he stuck a
mic element down into the throat of a huge ass horn.

If your speakers don't do 10 Hz (mine don't) maybe try some headphones.

JR
Visit https://circularscience.com to hear what properly "cleared" drums sound like.

emrr
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Re: Limiters with optocouplers

Post by emrr » Sun Mar 08, 2015 9:25 pm

Thanks JR, I'll check it out.
Best,

Doug Williams
Electromagnetic Radiation Recorders

carlmart
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Re: Limiters with optocouplers

Post by carlmart » Mon Mar 09, 2015 4:10 am

Going back to limiters, JRC is sending me some NJM2762 samples to see if they are any good as limiters or just garbage.

If they are reasonable, they could work on a small preamp version I'm working on.

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JR.
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Re: Limiters with optocouplers

Post by JR. » Mon Mar 09, 2015 10:51 am

That part is after my time so I never checked it out myself (I used my share of cheap gain cells like NE 570 family).

Looks like it will be better than clipping but just barely... The below limiting path is not very pure, but you can decide if it is clean enough for your needs. I am partial to limiters that are out of the path unless limiting, and I even experimented with using VCA's that way to make their already good nominal performance even better (downside is subtractive VCAs are cut only, but below limiting as clean as a simple op amp.)

JR
Visit https://circularscience.com to hear what properly "cleared" drums sound like.

carlmart
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Re: Limiters with optocouplers

Post by carlmart » Mon Mar 09, 2015 5:10 pm

That's why I asked for the samples.

Hopefully I can make the 4305 limiter work, when the parts get here, so I should have something to compare it with.

I'd prefer to bypass the 2762 completely when the limiter is off, and I might do that.

Bill Wilson
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Re: Limiters with optocouplers

Post by Bill Wilson » Mon Mar 16, 2015 10:23 am

Go online at Rolls Audio; look up the manual for the 422 field mixer. You will find a limiter implementation using vactrols & also low freq. cut on the output of their transformer less mike preamps.

carlmart
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Re: Limiters with optocouplers

Post by carlmart » Mon Mar 16, 2015 11:21 am

I have seen Rolls 422. and I'm not so sure I like their Vactol limiter implementation.

The filter is very simple, and I think my proposals on the other thread on HP are a bit better.

carlmart
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Re: Limiters with optocouplers

Post by carlmart » Mon Mar 16, 2015 2:57 pm

Has anyone seen a limiter built around this VCA?

http://www.thereminworld.com/Forums/T/2 ... uit?Page=0

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mediatechnology
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Re: Limiters with optocouplers

Post by mediatechnology » Thu Mar 19, 2015 10:49 am

Returning briefly to the subject of Vactrols...

Mammoth Electronics stock quite a few: http://www.mammothelectronics.com/category-s/84.htm

Thanks Bill for steering us to the Rolls MX422:

Image
Rolls MX422 Limiter Output Stage.

This is a very clever minimalist limiter.
A slight improvement could be made in the detector by splitting the junction of R23/R51 and duplicating C16 then summing both caps into D6.
That would make the detector chose the higher of Left/Right.
No current limiting on the Vactrol LEDS other than the transistor.
https://ka-electronics.com

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carlmart
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Re: Limiters with optocouplers

Post by carlmart » Thu Mar 19, 2015 11:34 am

Thanks for the tip on Mammoth: they are a bit less expensive than those from Newark.

A friend of mine told me that the place to get Vactrols is in China, for much lower prices.

I've opened another thread on FET limiters, as that seems to be an interesting type too.

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