Compressor or Limiter?

[Vivek]

Please help me to understand the curves that SPICE generated when I was studying a compressor.

I plotted output Vp for different input Vp at 1Khz between 0V and 1.5Vp input signals

Linear Linear Axes:



Log Log Axes :


My Log Log graph does not look like your Log Log graphs. Why ?

Have I to first log the values and then plot on a linear scale ?

[Vivek]

Admittedly, that what-happens-next aspect of compression is very difficult to illustrate with the simple transfer function graphs used, since it involves plotting gain recovery of a standardized input signal over time.  I can't fault you for not doing the impossible.   

https://www.uaudio.com/blog/digital-emulation-of-distinctive-compressors/

Interesting article on program dependent release of compressors

[amz-fx]

I have added the compression curve for the NE570 chip to the article at the end of Part 3.

Best regards, Jack

[Eb7+9]

good work Jack,

for fun maybe you can do the ALC version of the 570 ... see fig. 17 of AND8159

ie., from the DC2 schematic simply disconnect pin2 from pin3, leave ac feed from output to pin3 and run a separate cap from input to pin2

[amz-fx]

I took a look at the ALC version and the pcb that I made is not easily adapted to perform that action.

The standard 570 compressor is a feedback design and the ALC uses a feedforward detector.

I might look at more 570 uses later when I can get a few more NE570 chips.

Thanks for your comments!

Best regards, Jack

[GFR]

Some people may be shocked by this, but... guitar "compressors" are in fact limiters, and the "tremolo" bar is in fact a vibrato bar 

[rankot]

A really nice full range compressor for guitar is detailed here:
http://www.thatcorp.com/pedals/4316%20Battery-Powered%20One%20Knob%20Squeezer.pdf
I have this on my bass pedalboard, and it is almost always clicked on.
I have an LED bar graph on mine that shows when it is amplifying and attenuating, and by how much.

Did you build it on your own? If so, where did you buy that4316? It seems to be unobtanium.

[Ben N]

https://www.mouser.com/ProductDetail/THAT/4316Q16-U?qs=UsT9WWBIYFHRtMT94uCrzA%3D%3D

OK, so it's SMD, and OK, it's $3.37 plus shipping, but still.

[rankot]

Thanks a lot! Couldn't find it there for some reason!

[EBK]

A really nice full range compressor for guitar is detailed here:
http://www.thatcorp.com/pedals/4316%20Battery-Powered%20One%20Knob%20Squeezer.pdf
I have this on my bass pedalboard, and it is almost always clicked on.
I have an LED bar graph on mine that shows when it is amplifying and attenuating, and by how much.

Did you build it on your own? If so, where did you buy that4316? It seems to be unobtanium.

Yes, I built it on some vero, using an adapter board for the surface mount 4316 chip.
https://www.diystompboxes.com/smfforum/index.php?topic=116252.msg1075858#msg1075858

[Mark Hammer]

Note that it isn't a typo.  It really IS a 4316 chip and NOT the more familiar 4136 quad op-amp.

[Eb7+9]

Yes, I built it on some vero ...

Lovely work EBK

[Ben N]

Yes, I built it on some vero, using an adapter board for the surface mount 4316 chip.
https://www.diystompboxes.com/smfforum/index.php?topic=116252.msg1075858#msg1075858

Is there a switch in there?

[EBK]

Lovely work EBK

Thanks!

Is there a switch in there?

Of course!
There's also a microcontroller and an LED bargraph under there.  It's in a 1590BS enclosure.


I'm taking up too much space in Jack's thread.  My apologies.   

[Phend]

Question
How does this relate...?

[Eb7+9]

that dbx runs on early UPC1252H2 blackmer cells (NTE1794) ... THAT4316 likely blows them away

btw EBK, the RMS calibration is really a THRESHOLD control in disguise ... is it not?!

http://www.thatcorp.com/pedals/4316%20Battery-Powered%20One%20Knob%20Squeezer.pdf

[EBK]

btw EBK, the RMS calibration is really a THRESHOLD control in disguise ... is it not?!

Mostly/somewhat? It's a bit more interesting if you read this:
http://www.thatcorp.com/datashts/dn125.pdf

[Eb7+9]

EBK, found what was bugging me about this one-knob bizniss ...

in the one-knob doc it says:

"VR3 can also be a front panel control or user-adjustable
screwdriver trim to permit operating levels other than -20 dBu.
In pedal applications adjustment of instrument levels ahead of
the One Knob Squeezer will usually suffice and no external
adjustment of VR3 will be required."

---

front panel control ... a first confirmation from the author
the unit is assuming a nominal -20dbu signal ... so, it's a fixed threshold system
which they set to -20dbu

if we look at the circuit we see that VR3 is designed to inject a DC current (+/-) into the summing node of the nearby op-amp
and cause an offset at the output, which results in a lower or higher step to jump up from ... ie., producing variable Threshold

what they recommend doing is amping up an instrument level signal to meet -20dbu ... which means adding noise

rather, seems obvious to me, we could drop the 330k series resistor which is (current) limiting the Threshold variation to only +/-2dbu
then we might have a proper (ie., wide range) Threshold control ...
and thus match the response to a higher or lower level source without having to do anything to the source (ie., no added noise)

with the goal of making the circuit more compatible with lower Strat/Tele type signals ...