Reckless compressor - an original feed-forward diode based compressor

[jonny.reckless]

The music is from my band Saint Wry: https://open.spotify.com/album/76AYXUusxuLu0GiVGBQn6q

Really wanted to hear, but Spotify's not available in my country. 

https://play.google.com/music/m/Buof5bfbr4tog3pq3lzjvipbmmy?t=Wine_and_Honey_-_Saint_Wry

[rankot]

Nice! Kind of music I like to listen to while driving!

[Ben N]

Ben, which revision did you have? I can take a look and see if I have a spare PCB in my drawer somewhere.

Thanks Jonny, that's kind of you; I'll check, but I doubt very much it's a board issue, because it worked flawlessly with nary an issue for months. First thing I'll check board connections, try swapping chips, check caps & diodes, then a signal trace, and we'll see where we are.

[rankot]

Hi Jonny, few questions: I got a PCB set for Reckless diode compressor rev A.1 from you. I see there's also rev B.4 of this compressor. Should I proceed with building A.1, or make a vero for B.4? What's the difference in sound?

[jonny.reckless]

Hi Jonny, few questions: I got a PCB set for Reckless diode compressor rev A.1 from you. I see there's also rev B.4 of this compressor. Should I proceed with building A.1, or make a vero for B.4? What's the difference in sound?

I did a demo video of each. They are quite different. The rev B has an engineer's thumb style sidechain. The rev A has a much simpler average level detector sidechain, so it is more subtle and transparent IMHO. Rev B if you want a chicken picking squash. Rev A for transparent always on compression.

[rankot]

Hi Jonny, few questions: I got a PCB set for Reckless diode compressor rev A.1 from you. I see there's also rev B.4 of this compressor. Should I proceed with building A.1, or make a vero for B.4? What's the difference in sound?

I did a demo video of each. They are quite different. The rev B has an engineer's thumb style sidechain. The rev A has a much simpler average level detector sidechain, so it is more subtle and transparent IMHO. Rev B if you want a chicken picking squash. Rev A for transparent always on compression.

OK, I will build A, since I already have ETC.

[rankot]

I've been experimenting with using diode bridges in a compressor for a while. It's a very old school approach, but can be made to work really well, and it has a warm character to the tone which I really like. This is an original design, with a precision full wave rectifier feed-forward side-chain.

It's quite warm and characterful, but also can be set to be very transparent. It fits into a 1590BB.

Here is the circuit:

What is C10 here? DNF means "Did not fit" or something else? 

[PRR]

....DNF means "Did not fit" or something else? ...

Do Not Fit.

A component which might have been needed, but wasn't.

In this case, the V/I converter stability may depend on PCB layout, so provisions for a few-pFd cap were included, but it turned out the cap was not needed.

[rankot]

Jonny, what kind of cable and connector should I use to connect main and I/O PCBs?

[jonny.reckless]

Jonny, what kind of cable and connector should I use to connect main and I/O PCBs?

I just used a regular ribbon cable and IDC box header.

[freebird92]

Can I get any pcb or gerber files of rev A?

[rankot]

Can I get any pcb or gerber files of rev A?

It is pretty unusual that people with only one post in this forum ask for gerber files...

[freebird92]

Can I get any pcb or gerber files of rev A?

It is pretty unusual that people with only one post in this forum ask for gerber files...

Oh I was not familiar with this forum and DIY culture, so I didn't know it was disrespectful. I sincerely apologize for my inexperience and ignorance.

[bluebunny]

I don't recall Jonny releasing any Gerbers for this, although he did have a few boards made.  Try PMing Jonny to see if there are any left.  There's a vero layout on the previous page by andy-h-h.

[Ben N]

's-ok. Our welcomes are usually a little bit warmer. Welcome, freebird92!

You might want to PM Jonny. He's a friendly, helpful guy. I don't know if he wants to share his Gerber files, but that would be the way to ask. He also may have a RTS PCB to sell--I bought my Rev. B board from him, and am very happy with this comp.

Edit: Ah, great minds, etc., Marc.

[freebird92]

Hi. Thank you for enlightening my ignorance.

I reflected a lot. I realized that I had to try on my own before I asked someone.

So I made rev A on the perf board. It was difficult for me, but after a long time of debugging, I was finally able to complete it.

I put this in the input of the preamplifier.
Reckless compressor prevents the preamplifier from distorting.
And this helps to make uniform and good sound without reducing the dynamic range.

Thank you so much, everyone.

However, some questions arise.

I have a hard time playing with Time Knob because I don't know exactly how it works.

As the resistance of the Time Pot increases, does Attack and Realease time decrease? Or is it the opposite?

If you turn the Time Knob, something changes, but you don't know where it's appropriate.

[andy-h-h]

I made Rev A recently as well.  Turn the compression up until it's compressing quite hard, then try adjusting the time control.  The change in attack is easier to hear when it's compressing heavily.   In my opinion, just set it where it feels right, as for me compression is just as much about the feel as it is the sound.  Others may disagree.   

[jonny.reckless]

I don't have any PCBs left for the diode compressor(s).

PCBs for rev A and rev B of the diode compressor:
https://drive.google.com/drive/folders/1Apz7R7oSrA2EcCY_PMb7qlkBFp01aJwr?usp=sharing

You need the free Altium viewer:
https://www.altium.com/altium-designer-viewer

As always, non commercial use only, thanks.

Jonny

PS I have been tinkering with an idea for revision C of the diode compressor, mainly for vocals and studio use. This one will have XLR balanced in and out, and more flexible side chain options.

[jonny.reckless]

Jonny, what kind of cable and connector should I use to connect main and I/O PCBs?

I just used regular old school 0.05" ribbon cable and the IDC box headers on a 0.1" grid. If you get any noise issue (I didn't) try wrapping it with copper tape connected to signal ground, but I found having it in a grounded aluminum box was fine.

[bowanderror]

Thanks for posting this jonny.reckless, it sounds great! I've looked into doing some pro audio diode compressors but they tend to be pretty complex & have much higher rail voltages than the standard +-16V on my rack.

I'm building RevB.4 on vero, but had a few questions:

• On the vero layout andy-h-h posted on his VeroP2P blog, the Vref voltage divider resistors are upped to 10k from your schematic's 1k. Was the 1k chosen for impedance/current reasons?
• My 470uF electros are gigantic, did you find that this circuit requires that level of filtering? Looks like swapping them for 100uF like on andy-h-h's layout increases the fc from ~3.3Hz to ~16Hz, decreasing attenuation from -30dB to -10dB @ 60Hz. Based on that, maybe 470uF was on point!
• How close do you recommend matching the diodes? I've done some synth builds recommending <1-2mV, does this build require that level of matching?
• I'll probably match the diff amp transistors as well, not sure if you found that necessary.