Diode Based Compressor(Passive to Active)

joaquins · Jul 19, 2014

Using the 4148 you get less noise, because threshold is higher and more applicable for pro audio levels, so not a problem about that, still true the knee much softer, you can try with Ge diodes in series if you like more that way.

About the metering circuit, it's ok any meter you want to use, just add the buffer and inverter and then replicate the gain cell on the other side so you can measure that from a DC voltage.

JS

AMZ-FX · Jul 21, 2014

ForthMonkey said:
What about 1N34A? When i use 1N34A,it changes attack & release. Faster responses...It's easy to find germanium diode for me.

The 1N34a will be a good substitute for the AA119.

For best performance, I would match the forward voltage drops of the diodes so that D1=D2 and D3=D4.

Also, you don't need both R5 and R7 since they are in parallel. One resistor will do the job.

regards, Jack

ForthMonkey · Jul 21, 2014

About the metering circuit, it's ok any meter you want to use, just add the buffer and inverter and then replicate the gain cell on the other side so you can measure that from a DC voltage.

Can you show me any example for buffer and inverter? By the way did i take voltages from rights places?

The 1N34a will be a good substitute for the AA119.

For best performance, I would match the forward voltage drops of the diodes so that D1=D2 and D3=D4.

Also, you don't need both R5 and R7 since they are in parallel. One resistor will do the job.

I tried AA119 and 1N34a.They are adding distortion too much.4148 is the best to me for now.And i checked voltage drpos for 4148 and they are same values.

And you're right about R5 and R7.I'm still designing. ;D

ForthMonkey · Jul 23, 2014

Circuit updated.

Changed Output Control and added values.

Pot values not okay for now.Still calculating...What about bypass?Is this ok?And what about bypass resistor value?

ForthMonkey · Jul 24, 2014

Any idea to taking voltage for GR meter?

ForthMonkey · Jul 30, 2014

I'm still waiting for your answers,masters! :-\

I breadboarded circuit and working great.Now i will make pcb but first i have to be sure about GR meter.

ricardo · Jul 30, 2014

This type of compressor doesn't have a sensible 'Control Voltage' which is what is usually metered for GR display.

The 'control' quantitiy is actually the DCcurrent through the diodes. Extracting & displaying that sensibly may be more complex than the rest of the circuit.

... over to those who like challenges. But forth, make sure you try out any of their pie-in-the-sky ideas for real before investing in expensive parts.

ForthMonkey · Jul 31, 2014

What about this idea? I can see reduction,i guess.

ricardo · Jul 31, 2014

ForthMonkey said:
What about this idea? I can see reduction,i guess.

No idea what that will show but its definitely NOT GR.

ForthMonkey · Jul 31, 2014

ricardo said:
ForthMonkey said:

What about this idea? I can see reduction,i guess.

Click to expand...

No idea what that will show but its definitely NOT GR.

???

There is no way to add GR meter?

ricardo · Jul 31, 2014

ForthMonkey said:
There is no way to add GR meter?

Someone cleverer might have different ideas but I can only see methods which are more complex than the rest of the circuit put together.

Why do you need a GR meter?

hakanai · Jul 31, 2014

I would go with joaquins' idea of a simple led indicator when compression is happening. precise gain reduction has always been a bit overemphasized to me. The perfect GR meter for me would be 2 led, -1 and -6. That's it. I would know everything I need to know with that much metering. But even that is overkill quite often. I think a "It's happening" light would be perfect for this box. Get a guitar amp power light jewel housing like this:
http://www.guitarpartsresource.com/images/large/099-0950-000.jpg
stick your led in there, and I think your in good shape.

samples sound cool. Definitely has a home on a drum bus. Would like to hear some samples on other sources (a nice stereo piano or a cleanish complete mix are always telling)

Don

ForthMonkey · Aug 1, 2014

hakanai said:
I would go with joaquins' idea of a simple led indicator when compression is happening. precise gain reduction has always been a bit overemphasized to me. The perfect GR meter for me would be 2 led, -1 and -6. That's it. I would know everything I need to know with that much metering. But even that is overkill quite often. I think a "It's happening" light would be perfect for this box. Get a guitar amp power light jewel housing like this:
http://www.guitarpartsresource.com/images/large/099-0950-000.jpg
stick your led in there, and I think your in good shape.

samples sound cool. Definitely has a home on a drum bus. Would like to hear some samples on other sources (a nice stereo piano or a cleanish complete mix are always telling)

Don

I can make led indicator but i can't imagine from where should i get voltage and how?

hakanai · Aug 1, 2014

joaquins said:
There is no simple way to do that, and this is a simple compressor which shouldn't be looking for that. Between P1 and R4 you will have some voltage changing in some function of compression, but I wouldn't use that more than for knowing it's compressing or not, maybe one led called 'activity' or something like that.

You just need to reference your older schematic (which is not in the thread anymore)

ForthMonkey · Aug 1, 2014

hakanai said:
joaquins said:

There is no simple way to do that, and this is a simple compressor which shouldn't be looking for that. Between P1 and R4 you will have some voltage changing in some function of compression, but I wouldn't use that more than for knowing it's compressing or not, maybe one led called 'activity' or something like that.

Click to expand...

You just need to reference your older schematic (which is not in the thread anymore)

My old schema in first post.I added meter pin.Can you check?

frizze · Aug 10, 2014

in this way make the difference between in and out, get a linear scale if I'm not mistaken.
inserting a logarithmic converter should be able to drive the vu!

300px-Op-Amp_Logarithmic_Amplifier.svg.png

joaquins · Aug 10, 2014

That's true, there you have your meter, take R11 out and make your output pot 500k or 1M, I think I used R9 to change the ratio instead of R8 and R18, but I don't remember exactly, that way with a dual pot you use the other side for your meter, changing the ratio will change your level but low interaction if the output pot is high enough. For your meter I'd add some buffering, maybe you could pick your points after R8/R18 so you leave it this way and you don't need to add a pot for the meter, then add the diodes and R9 to a variable DC, set that DC for zero on the meter, and R9 for good tracking, that would be it.

JS

ForthMonkey · Aug 13, 2014

Thanks for responses!

Now i can build prototype.Then i will work on meter design.

joaquins · Aug 13, 2014

You still don't have a prototype?? Come on! your samples on the breadboard sounded nice!

You are missing an input control to be able to control the threshold, we discuss it, it have to be buffered, but would be nice to have, if not, at least a couple of diodes to select between to be able to do something about it in steps.

JS

Diode Based Compressor(Passive to Active)

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