ssl external sidechain

Hello,

I am a newbie here so I appologize

I am just finishing building 3 SSL clones and wonder if anyone can answer a question regarding the sidechain modification.

I do not wish to have the balanced in/outs as these units would only be sidechained for ducking. I read the simple solution for mono of taking the two to sidechain signals through two 4k7 resistors for a send. I also noticed the diagram by Mathias. Without the modification the left and right are summed together through two 47k resistors = 94k. With the simple modification based on the diagram, the two channels are summed together through two 4k7 resistors for a send. The return goes through the two 47k resistors. Note that based on the diagram, when the unit is not connected to a send, the signals are now being summed into the two 47k resistors but the 4k7 resistors are in parallel with the 47k's giving 8.5k. Does anyone know if this is o.k? This will affect the send signal and what is going to the sidechain VCA. I don't know if audio is affected.

 Advice appreciated

Thanks

I don't understand exactly what you mean.
When not in side chain mode, the signal is beeing summed by two 47K resistors, that's it. There is also a switch which selects between the signal from the two 47k resistors and the signal from the return which goes to paralleled 47k resistors. When your not using the return (and set the switch accordingly) the signal goes only through the two 47k resistors before it reaches the vca....

SO after getting the PCBs from Greg, i am about to design my front panels..


are the frequencies really 60, 90, 130, and 200?? if not what are they

cheers
-d

[quote author="quadwould"]...
are the frequencies really 60, 90, 130, and 200??...
-d[/quote]

yepp :sam:

Keep in mind you can make them whatever you want by the appropriote R and C in the first order high pass...

fc = 1/(2*pi*R*C) :thumb:

I'm looking to add an external side chain, but I'm a little confused between the options.

Jakob, your suggestion seems quite simple but I don't understand why the circuitry that comes before the internal sidechain does not need to be re-created for the external. Is it because that initial circuitry is converting the balanced signal to unbalanced and the sidechain is just using the hot and ground (unbalanced signal)?
Maybe I'm not understanding the concept correctly. I only have some experience with electronics.

Thanks!

Yes, the signal is unbalanced at that point, and also predictable and rather low source impedance (because it's directly at the output of input opamp).

It should work, but note that I have not tried this in real-life!

Jakob E.

Is it still possible to get the external sidechain PCB? from Greg? or?

Jørgen

There is now a 'super sidechain' PCB which has all of the filter stuff plus the 'thrust' options.
You can get it from Gustav.
See 'White Market'.

barclaycon said:

There is now a 'super sidechain' PCB which has all of the filter stuff plus the 'thrust' options.
You can get it from Gustav.
See 'White Market'.

Click to expand...

where can I find more information about these 'thrust' options??

Do a search. There was a lot of discussion about this on the forum.
The thrust idea comes from API who used it on their 2500 compressor.
Clintrubber did a lot of research into the design and came up with a circuit, but API weren't too happy about their design being used. That's why there isn't a whole lot of documentation around!

a final skeme (jpg)
will be a really welcome news
8)

barclaycon said:

Do a search. There was a lot of discussion about this on the forum.
The thrust idea comes from API who used it on their 2500 compressor.
Clintrubber did a lot of research into the design and came up with a circuit, but API weren't too happy about their design being used. That's why there isn't a whole lot of documentation around!

Click to expand...

That is the problem! I have searched a lot around on this forum for weeks now. Noticed that the design of Clintrubber has been sadly removed due some comments from API.
If anyone has it, please let me know where I can find it or pls email it to me...
Have some space restrictions in my case and want to put 2 sidechains inside. The other functions such as on the off/on switch, relays and VU lighting will be transferred to a seperate PCB that is mounted on the backside of the frontpanel.
thx

Have you considered sending a PM to clintrubber ?

barclaycon said:

Have you considered sending a PM to clintrubber ?

Click to expand...

Don't want to disturb people to much but will try. Thanks...

Hello  , just one question .

my gssl is rev .7  pcb .

want to add the internal  simply hpf  on board sidechain filter implimented on rev11.
on this pcb the "hpf" holes are not present
somebody can help me to connect it?
thanks in advance.

cray,

Look at the new schematic, and relate to PCB - insert point location should be obvious.

Jakob E.

Thanks Jakob.

i ve  found  it!

Here's a simple HPF setup that's quick and requires no new boards.  Feed the signal from the two 47k resistors feeding the sidechain to one side of a DPDT switch.  The off position returns to the 15k resister at the sidechain input.  Connect the on position to the off position with the capacitor across the two contacts, on the switch itself.  When switched on the signal will return through the capacitor and when off the signal will bypass the filter.  I used a .047uF Wima 63V on mine, which will give you a 6dB/oct. at 225 Hz filter.  No resistor is needed on the switch, because the 15k at the sidechain input going to ground completes the filter.  The other half of the switch can be used to switch an LED if desired.

Hard to find.. qith so many posts

thanks!