ssl external sidechain

There was a bunch of info about putting an external sidechain on the ssl in the other forum. I only have bits and pieces.

I thought I would start a thread for it hopefully we can gather info again on how to do it.

If I remeber correctly there were a couple of different ways people were approaching it.

thanks.

chris

An approach for a (mono) sidechain insert could be:

Take the two "to sidechain" signals, and add them together with two 4K7 resistors.

This becomes your insert send.

Connect the two 47K's at the input of the sidechain together.

This becomes your insert return.

Use a tip/ring stereo jack socket. Send to ring and return to tip. Normalize ring to tip. This way you can also use the insert as an input (for ducking etc.), and if no jack is inserted it will just act as a normal clone.

Result: Insert point output impedance ~2K5, input impedance ~25K.

This should be good enough for most purposes.

Unless I missed something - I havent really slept enough the latest couple of days..

Jakob E.

I remember people were suggesting various ways to do it as well.

If I recall correctly some of the other ways people were suggesting it be done was to buffer the sidechain inputs; another was to cut the track just before the VCA.

In the second case, I believe Jakob had made the comment that it wouldn't work because the VCAs are current-in/current-out devices with zero ohms input impedance. So he suggested the solution he posted above.

Hope that saves some grief if someone still remembered the cut-the-track-before-the-VCA solution and thought it would work.

[quote author="gyraf"]
Use a tip/ring stereo jack socket. Send to ring and return to tip. Normalize ring to tip. This way you can also use the insert as an input (for ducking etc.), and if no jack is inserted it will just act as a normal clone.

Jakob E.[/quote]

Couldn't I just use a mono socket with normalising lug. At least if I don't connect it to a patch bay. Otherwise I would have problems if I put a mono lead into the socket?

If I would connect it to a patch bay Jakob's example would be necessary... or am I just confused now?

The way I did it (Jacob explained this in another SSL sidechain thread on the old TT forum) is: cut the two sidechain traces before the two 47K resistors, take them together each thru a 4k7 resistor, this is the send.
The return will go thru the two 47K's in parallel.
To make my sidechain balanced I added the input and output stage of the SSL clone.
I tested this by connecting the balanced send to the balanced return and it seemed to work. I had to re-adjust the threshold to compensate for the volume difference of the sidechain but besides from that it worked fine.
I have not tested the sidechain with a EQ or a trigger signal though....
The sidechain will be switched by a relais.
I think I will also make a sidechain listen function so I can hear the EQ tweaks or the trigger signal.

Maybe a stupid question... but i never do these. How I can normalize the ring to tip. In general, how I can normalize outs and inputs....
Thanks

Arnau

If there is a switch in the jack, that is activated when a plug is inserted..

I'll do it this way:




is that correct :?: :?:


mm

aaaaahh.... oks... there is a switch on the jack, mechanical... thanks! where type of part is? or where I can buy that type of switched sockets?
... i ever asked myself for that question, I suposed that it could be with mechanical switch, but never be sure, thanks for the info


Arnau

ups... I found it in a catalogue...
Thanks guys... is the Mathias schem correct?

Arnau

[quote author="Apache5"].. is the Mathias schem correct?[/quote]

It looks right to me.

Hi, Im building SSL now and I want to implement the sidechain option. I have one neutrik stereo switched (NC) jack plug socket and im trying to find the correct schem... I found one possibilty but with that I use the sleve contacts to pass the board control signal when no jack is inserted. Is that correct? there will be ground problems if I plug a jack with grounded sleve? what is the correct wiring schem with a stereo switched plug socket to obtain a sidechain?
Can anyone help me with that? i must stop the SSL construction until I can do the correct... :sad:

Thanks for all your help in that and other questions that I usually do

Arnau

The schem that i imagine is that


Can it runs ok?

I use the Matthias pic to draw mine... hope that it dont matters he

Arnau

Can it runs ok?

Click to expand...

The circuit right above won't work I'm afraid. The sleeve on such jacks has usually switching too (like those black plastic Re-An types), but you can't use it here.

I like the previous circuit, by just adding a switch. If you choose to skip an inserted external processor you simply hit that switch and don't have to rely on a bypass that could be meters away - and you can still keep everything wired up.

I'd also go for two separate jacks (sidech. send, sidech. return) if you have the rear-panel space. It'll avoid the potential confusion for insert plugs. Since:

Use a tip/ring stereo jack socket. Send to ring and return to tip. Normalize ring to tip. This way you can also use the insert as an input (for ducking etc.), and if no jack is inserted it will just act as a normal clone.

Click to expand...

I understand this as being the convention for 'serious non-prosumer' gear, but as I'm still living in/near Mack. & Beh.-country , I face the usage of Tip=Send & Ring=Return. Using two jacks would solve this without having to think too much about wiring it up.

Bye,

Peter

Oks... thanks for your reply. I try to do it with two switched jack plugs I havent the space in front plate to put one switch more ( I drilled it some days ago). I try with switched ones or I could try to do it with XLR plugs and a switch when I will change the front plate... If I cant use the switch of the jack plugs I can put xlr sockets that i like more and just use a switch.
Could you explain me why my circuit not runs? I cant see the "reason" and Id like to learn. My sleve is switched too and I cant see why it is not ok if I take care in not connect the jack sleve to ground in my insert cables..
Thanks Peter for your help :wink:

Arnau

Hmm, while it's not impossible, or probably quite OK to use the sleeve for 'signal' instead of 'ground'/shielding, it's not common or advisable. There could be thought of an arrangement, but that would make things unnecessary complex for the things you want to do here.

Thanks Peter... I'd try the option to separate send and return with two plugs... I really like it more too... :razz:


Arnau

I'm trying to add a high pass filter with selectable frequencies in the sidechain of one of my SSLs. I was thinking about using a circuit posted by Steffen some time ago.



I breadboarded this design and it worked, but I read in this thread that the VCA is a current in device, with zero ohm input impedence. I also noticed that this sidechain filter has less than unity gain.

Any comments on the matter... I'm a little confused?

[quote author="Greg"]I'm trying to add a high pass filter with selectable frequencies in the sidechain of one of my SSLs. I was thinking about using a circuit posted by Steffen some time ago.



I breadboarded this design and it worked, but I read in this thread that the VCA is a current in device, with zero ohm input impedence. I also noticed that this sidechain filter has less than unity gain.

Any comments on the matter... I'm a little confused?[/quote]

dont forget the 47K resistor between the SC circuit and pin1 of the sc vca. I reduced the gain of the circuit because the threshold was too low then....even with the threshold pot fully counterclockwise it was still compressing a litte on high input levels....


steff

Thanks Steffen. Let me make sure I have this implementation correct. I take the TO SIDECHAIN points to the FROM INPUT BUFFERS of your filter, then the TO CONTROL AMP goes to a 47K resistor to pin 1. What about the 100p and 15K from pin 1 to ground. Does that stay, or go?