How to add side chain on 1176 comp?

[xarolium]

Hello everybody

I'm a newbie frog on the forum.
I want to build a 1176 but i want to add a external sidechain with a filter
and a bypass switch
i seen it here
http://www.groupdiy.com/index.php?topic=11151

and i don't know how he made it
i'm waiting for your help
thank you very much

 

[SSLtech]

On the GR disable switch (attack time all the say to the left) on an 1176, the GR is disabled by muting the sidechain. All you'd need to do is add a send buffer, a return buffer and break the signal at this point.

Connect the outgoing side to the input of the send buffer, connect the incoming side to the output of the return buffer, and add some sort of linkage or switch to connect the send & return terminals for when the sidechain is not in use, or add an SPDT switch to connect the sidechain return to the sidechain send, effectively re-making the connection which you broke, but simultaneously disconnecting the sidechain return buffer from the sidechain input... you can connect one signal or the other, but NOT both at the same time. Two outputs don't connect to each other and play nice.

Keith

 

[xarolium]

ok i've not all understand but i think that i must connect a jack on the meter board but can you show me please on witch Pad and How i connect this ?

Thank you for your help

 

[Sleeper]

check out the purple mc76 schematics. they have an external sidechain buffer, I think its on the last page.
Kelly

 

[xarolium]

Thank you Sleeper

I look the schematic here http://www.purpleaudio.com/pdflib/PurpleMC77v34.pdf
But what explain SSLTech isn't exactly what's on the schematic ?
If i want to add sidechain i must build a VCA ??

 

[Sleeper]

what ssltech describes is insert loop driver and insert loop return.
Every compressor already has a sidechain.

you must build the insert loop driver and insert loop return amplifier..,
you would need to build the voltage divider as well... it's needed for the power requirements of the buffer amps.

Greg/Steffans ssl sidechain boards have a buffer amp as part of the design but you can't run it straight off of the 1176 power rails. If you don't quite understand what the sidechain circuit is-please don't take offense- but... you might be a bit green to go severing the purple circuit from the schematic and designing a pcb.

It might be best to buy the filter boards from greg and build a separate +-15v power supply for them, then hook them up as ssl recommends or as indicated in the purple schematics.
sleeper.

 

[hymentoptera]

Sorry to dredge up this oldie, and perhaps this belongs in another thread, but I was wondering if anyone has used the Hairball Stereo Link board as a buffer for sidechain insertion?

Seems you could just use another switch to select between internal summed signal and external input? Or is the stereo board even necessary for this?

 

[ferrochrome]

Sorry to dredge up this oldie, and perhaps this belongs in another thread, but I was wondering if anyone has used the Hairball Stereo Link board as a buffer for sidechain insertion?

Seems you could just use another switch to select between internal summed signal and external input? Or is the stereo board even necessary for this?

Bump. I'd really like to know this as well.. Have two rev d mnats w stereo link, if I could just add some  wires and a trs that would be great!

 

[mitsos]

hmm, why not try it and let us know?

 

[ferrochrome]

You're right, but nice to know if someone be experienced with it. So many things to do and not enough time..

Here's my easy fix: Sometimes I insert one of the 1176 channels, switch in the link and send a second sidechain to the "unused" channel. So I have the external sc mixed with the internal, this works but would be nice to be able to use ext only, and both channels at the same time.

 

[hymentoptera]

I wonder if the buffer is even necessary. Depending on sending source, you should be able to set up the insert gain just the way the GR amp in the 1176 is expecting it. That's why I'm thinking the stereo board might be perfect for this.

Whether I use the stereo board or not, I'm thinking of maybe installing a "normalled" shorting jack between the output pot and pad 15 on ratio board, probably front panel mounted for easy access, and with nothing inserted the unit behaves as normal, but when a TS jack is inserted, the internal signal coming from the output pot / pad 15 on main board is interrupted and instead sees the injected signal hitting pad 15 on the ratio board.

It all depends on expected signal level and impedance. I think that's why previous posters suggest a buffer. Otherwise you could use a separate send and return and insert maybe an EQ for hi pass filtering or deessing. Gaining access to the 1176 sidechain opens up tons of possibilities!

 

[hymentoptera]

I think I've got it!

Build two units, w/ a Hairball stereo board and link switch in each, but instead of swapping Tip and Ring on stereo link jack inside only one unit, just make the Tip Send and Ring Return on both. Now if you choose to simply connect them as usual, just build a short custom link cable with Tip and Ring swapped on one end.

But here's where it gets crazy: Instead of a short custom cable, run your link lines out to a fully normalled patchbay channel, and swap the tip and ring there at the patchbay normalling points. Now with nothing patched in, the compressors behave as normal; with both link switches engaged they act as any other stereo 1176 pair.

Now, If you want to access your sidechains, just patch in at the patchbay! Use a "insert cable" to access the sidechain however you want. You could inject a signal into the Ring side (if that's what you chose for returns) to duck, or use Tip and Sleeve to insert an EQ to de-ess, etc.

Does anyone see any problems with this setup? Other than potentially long unbalanced runs?

Thoughts? Comments?

 

[dmnieto]

I think I've got it!

Build two units, w/ a Hairball stereo board and link switch in each, but instead of swapping Tip and Ring on stereo link jack inside only one unit, just make the Tip Send and Ring Return on both. Now if you choose to simply connect them as usual, just build a short custom link cable with Tip and Ring swapped on one end.

But here's where it gets crazy: Instead of a short custom cable, run your link lines out to a fully normalled patchbay channel, and swap the tip and ring there at the patchbay normalling points. Now with nothing patched in, the compressors behave as normal; with both link switches engaged they act as any other stereo 1176 pair.

Now, If you want to access your sidechains, just patch in at the patchbay! Use a "insert cable" to access the sidechain however you want. You could inject a signal into the Ring side (if that's what you chose for returns) to duck, or use Tip and Sleeve to insert an EQ to de-ess, etc.

Does anyone see any problems with this setup? Other than potentially long unbalanced runs?

Thoughts? Comments?

Or you can use my board

I can send you one the spare one if you want to test it

 

[hymentoptera]

I think I've got it!

Build two units, w/ a Hairball stereo board and link switch in each, but instead of swapping Tip and Ring on stereo link jack inside only one unit, just make the Tip Send and Ring Return on both. Now if you choose to simply connect them as usual, just build a short custom link cable with Tip and Ring swapped on one end.

But here's where it gets crazy: Instead of a short custom cable, run your link lines out to a fully normalled patchbay channel, and swap the tip and ring there at the patchbay normalling points. Now with nothing patched in, the compressors behave as normal; with both link switches engaged they act as any other stereo 1176 pair.

Now, If you want to access your sidechains, just patch in at the patchbay! Use a "insert cable" to access the sidechain however you want. You could inject a signal into the Ring side (if that's what you chose for returns) to duck, or use Tip and Sleeve to insert an EQ to de-ess, etc.

Does anyone see any problems with this setup? Other than potentially long unbalanced runs?

Thoughts? Comments?

Or you can use my board

I can send you one the spare one if you want to test it

Yes please? You've got my attention.

 

[dmnieto]

Yes please? You've got my attention.

This is the board, http://groupdiy.com/index.php?topic=44882.msg700032#msg700032

I am going to update it to make build easier (it has lots of smd components), but if you want a freebie and feel the challenge i can send it to you. Check the schematic. I can also share a BOM, but you may want to hunt for cheaper components (the relays are very expensive, but I chose those to avoid crosstalk).

PM me if you are still interested

 

[hymentoptera]

a couple of things, i don't mess with SMD as I don't really have the right tools, and as my making stereo pairs I would need two of your boards, BUT it looks like a great idea, and it seems like the next version (I hope you continue development!) will correct some issues and might even surpass the hairball board in popularity since it offers so many great features!

Since I already have 4 Hairball kits I think I'll try my idea out first. Then I can insert any EQ, filter, whatever in the sidechain, and if there's any issues I can always revert to using the special polarity invert cable and use the compressors as intended.

Keep developing the filter/bypass board! I'd love to eventually work a proper bypass into an 1176 without drumming up my own PSU for relays, etc.

 

[dpdp]

Does anyone have a working link for the mc77 schematic? I've also been looking into doing a side chain on my 1176.

 

[scott2000]

This?

https://www.purpleaudio.com/product/PurpleMC77v34.pdf