Need some help understanding this SSL schematic

[dustbro]

I'm still very new to the whole DIY thing... built a few projects and I'm having a ton of fun.
I'll looking to build a no frills DIY SSL channel strip compressor (not quad bus comp)... no sidechain, gate, etc.. just compressor. So I need help on determining which section from this schematic is the compression section. I'm assuming its the general area around the AD536J chip, but the dbx chips were used in the Gssl project.. so that leads me to the top of the schematic. If someone could help me figure out where and why, that would be greatly appreciated.
Also, what diodes are 1544? I see where they are located on the schematic, but cannot find any specific info on where to buy and exactly what they are... same with the 1/4 CA234 IC chips.

 

[SSLtech]

"1544" = IS44. Use 1N4148's or whatever -basically just a standard glass signal diode.

You can't "remove the sidechain". If you did, you don't have a compressor, you have a VCA.

A quick explanation:

Everything from C10 to R84 is the VCA and audio path.

Everything from C1 to the R11/R12 junction is the RMS/DC block.

Everything from R12 to D18 is the comp/lim DC path.

Everything from R34 to D16 is the Exp/gate DC path.

The ten-opamp bit (2x 5-op-amp ladders) at the bottom is two 5-LED meters (for GR display)

Before you go any further with this, I really suspect that you might not understand how difficult this may be to build. -The AD536J is the precision log-output RMS-DC converter. Look at the schematic; it drives both the compressor and the gate circuits.

Have you tried to source the AD536J yet? -If so, let me know how much you can find one for, then maybe think about building this circuit.

CA324E is a quad op-amp of very general characteristics. No audio passes through any of them. TL074s or more or less anything else will work... but this is all academic if you can't get the RMS-DC converter.

Keith

 

[CJ]

Eat your heart out:

:shock:

You can add a buffer to the 737 and get the same thing, I think.

 

[dustbro]

Holy **** Keith! I absolutely have no idea how hard this will be to build. Compaired to a few other projects floating around out there, this one seems a little on the easy side (if you are just looking at a schematic.) I wanted to do a few projects from scratch cause I'm very interested in this whole process. 98% of me wants to lean how this stuff works, and 2% of me wants cheap knockoffs of great sounding gear. I'm also working on a rebuild of the Roger Mayer RM57/RM58... should be fun as well.
I'll see if I can get the BOM going. That will give me a good idea if this project is possible.
I really appreciate the post. You're a life saver.
Dan

 

[dustbro]

[quote author="CJ"]Eat your heart out:

You can add a buffer to the 737 and get the same thing, I think.[/quote]
CJ, would this be a replacement for the AD536J? Not exactly sure what you are showing me.
Thanks

Dan

 

[dustbro]

[quote author="SSLtech"]
You can't "remove the sidechain". If you did, you don't have a compressor, you have a VCA.
[/quote]
I was under the impression that this was an external sidechain... used for controlling the vca from an external audio source. like ducking and stuff like that.

 

[Svart]

no he's right, those are for led driving, likely a cheap comparator IC.

the AD536 is easy to get but costs 12-17$ each.

 

[Svart]

the 737 would not work, it only has a BW of 33hz.. the other AD offerings are odd voltage rails too.

 

[clintrubber]

[quote author="SSLtech"]Have you tried to source the AD536J yet? -If so, let me know how much you can find one for, then maybe think about building this circuit.[/quote]
Right, these aren't cheap. :? I still have a AD636JH (metal can) here, new, unused. I think I paid around 55 Dutch guilders (~ EU25) then for a 'dB-meter' project.

 

[Svart]

it might be cheaper to roll our own rms converter with some opamps and some diodes..

 

[dustbro]

[quote author="Svart"]it might be cheaper to roll our own rms converter with some opamps and some diodes..[/quote]
Now that would be totally over my head. I'm having a hard enough time copying someone elses design!

 

[dustbro]

[quote author="Svart"]
the AD536 is easy to get but costs 12-17$ each.[/quote]
Where would you find them? I haven't had any luck.. been emailing places like www.usbid.com that source out hard to find parts.
Dan

 

[SSLtech]

SSL stopped using them a few years ago. They have a small number of stock-on-hand for repairs and service, but I bet they won't be cheap!

SSL now uses SSM detectors in their X-Logic, J and K-series consoles.

CJ, These are 14 or 16-pin devices with a big gold plate on the back, not yer little 8-pin nonsense... :green:

Keith

 

[dustbro]

[quote author="SSLtech"]SSL stopped using them a few years ago.

SSL now uses SSM detectors in their X-Logic, J and K-series consoles.[/quote]
What is the sonic difference between the 2? I'm a much bigger fan of the G series channel strip comp than the 9K. If I were to move forward with this project, would it be wise to retrofit this new chip in place of the old?

 

[Svart]

Digikey has tons of them in stock. :wink:

Digikey carries all of the Analog Dev stuff.

 

[dustbro]

[quote author="Svart"]Digikey has tons of them in stock. :wink:

Digikey carries all of the Analog Dev stuff.[/quote]
the AD536J? What's the part number? I cant find it on DigiKey

EDIT

OK... found
AD536AJD IC TRUE RMS/DC CONV 14-DIP $15.48
AD536AJH IC TRUE RMS/DC CONV TO-100 $11.25
AD536AJQ IC TRUE RMS/DC CONV 14-DIP $11.25

What is the one I need? What is the difference??

 

[dustbro]

[quote author="SSLtech"]"CA324E is a quad op-amp of very general characteristics.[/quote]
Do you mean the CA234?

 

[clintrubber]

[quote author="dustbro"]
AD536AJD IC TRUE RMS/DC CONV 14-DIP $15.48
AD536AJH IC TRUE RMS/DC CONV TO-100 $11.25
AD536AJQ IC TRUE RMS/DC CONV 14-DIP $11.25

What is the difference??[/quote]
Most likely the package-style, as you actually already listed. See datasheet for confirmation.

Regards,

Peter

 

[Boswell]

Of the ones on that list, go for the AD536AJQ. You don't need to spend the extra for your intended use. The 14-pin DIP package is easy to get sockets for.

 

[Michael Tibes]

I wonder if the AD536 could be replaced by THAT 2252 http://www.thatcorp.com/2252desc.html?

Michael