SSL 552 Summing Box

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helterbelter

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Update :
The mods for turning a 552 into a summingbuscompressor are described in this updated first post : Scroll down for the "htdiy"
(how to do it yourself)
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Hi there,

I've got quite a lot of emails recently with questions how to wire the SSL SL552 IMO module, so I've decided to start a new thread for this.

First, let's tell what a 552 IMO actually is !
IMO stands for Independant Main Output. Basically, it's this :
stereo summing amp > balanced inserts> masterVCA> balanced inserts> balanced output. There are a few more bells and whistles, but not interesting enough to take into consideration for building a summingbox.

Regarding the summingamp : it uses MAT02 as summingfront end and is completely identical to summingstage as the SL557 module which is the masterbus of the 5000 broadcast console.
(a sidenote: SL557F is a 5000 Filmconsole module, which doesn't handle audio).

Here's the block diagram. Ignore the external input, TB input, and everything below that. It's of no use (although the external input can be of use).
Description_SL552_003.jpg



Here's the pinout diagram. The last stage is used solely for adding the talkback and tone inputs to the signal, so, you can discard that for the standalone racking : Simply use the post vca sends as outputs.
In case you want to use the last stage : The postvca insert can be jumpered on the DIN41612 using common jumperblocks as used in computers. a drop of soldering will do the trick as well.
The connectors you need for this are 2x DIN41612 sockets (not plugs!), 96 pin ABC, or 64pin A+C.

SSL552wiringdiagram.jpg





This is a way to make a passive summing resistor network that will work with these modules. Note that it's be best to use low tolerance metalfilm resistors, or handmatch them in sets of four.  SSL usually uses 0.1% tolerance for the audiocircuits (although they don't use passive summingnetworks in their designs). Connect all the ground/sleeves of the inputs  to the ground of the SSL module.
One thing that has to be noted : This summingnetwork is something I found in the SSL docs, as an alternative for the standard active summing that’s used in the 5K console.  However, together with the summingstage of the 552 this gives a boost of 6 dB. Kante and I have experimented with shunt resistors, but it’s not possible to get it right with only a shunt. (Increasing the 10K resistors to, say, 20K, should be an option though).
SSLsummingstage.jpg

In case you have a few unbalanced lines that you want to add to the summingnetwork, it'd be best to wire the ground/sleeve of the output to the negative rail, and the plus to the positive rail (both via a 10k resistor of course). Don't connect the ground of the output to the ground of the summingnetwork.

Another good option, is to use the NYD design passive summing network. It’s somewhere here on the groupdiy site, so, hit the search button !
Udo is currently building a NYD summingnetwork, check this : http://www.groupdiy.com/index.php?topic=43999.msg595461#msg595461

PSU :
Regarding the PSU for SSL5k modules : I recommend the JLM audio 5 rail powerstation kits. a dual 18vac torroid in front will give you the desired voltages via the standard regulators.
If you're building a PSU solely for the 552, you could also use the 3 rail psu, and reverse the doubler rail into a negative doubler rail : You should reverse the caps and the diodes in the doubler circuit (including the chargepumpcaps), and use a 337 instead of a 317. This way a dual 15VAC torroid will do the trick. Note that the pinout of a 337 is different than the 317, so you should wire this one offboard.
EDIT : post from mrclunk and SSLTech :
mrclunk said:
Also the -24v rail is just for logic so doesn't need to be regulated.
So u could just tap off the -24v (ish) after the bridge and filter caps of your psu if using a 18-0-18vac transformer. 
I have tested this also, and it does work, as long as you don’t use more than 2 or 3 modules. So, for only the 552, this is a cost effective, simple solution.

Oh, and before I forget !
Keep in mind that the amp produces heat, so, make sure that there's enough space inside the box.

so here it is. I hope you all like this project, and goodluck building yours !  :)

---------------------------------------------------------------------------------------------------------------------------------
here are a few pics again of the 12 stereo input unit that I built a few years ago. Not that supergood looking, I know, but the wiring is done decently, and its sound is simply great. The summingresistor network is soldered directly on the sub-d inputs.
(btw, I haven't got this unit anymore, simply because I have built a bigger one, with 3 subgroups and active summing. )
inside-1.jpg

insidesideview.jpg

back.jpg

……………………………………………………………………………………………………………………………………………………

Edit 24-11-11 :

Here's my recently finished SSL Summing Station Lunchbox :
http://www.groupdiy.com/index.php?topic=43999.msg585977#msg585977

Edit  1 Februari 2012 :

Here’s the necessary info for  turning the 552 into a serious GSSL

Simply, by adding the GSSL sidechain stuff to the IMO’s VCA’s. This is even more simple than building a GSSL.
With this setup, you have an all complete SSL audiopath, with original SSL balancing and debalancing chips, paired temperature compensated DBX/THAT VCA’s for each channel, and of course the SSL summing stage as a luxurious bonus. (which you don't necessarily have to use : You can enter the VCA stage at the pre-vca insert return, thus bypassing the summing circuitry, so you can use it as standalone compressor also !)

What to do, is tapping off the audio signal in front of the VCA’s of the 552, route that to the sidechain circuit of a GSSL, take out the CV from the GSSL, and wire that to the 552 again. Wickedly simple !

Here the schematic and layout  with the notes.
The 552 (just one channel shown by the way).
SL552modification.jpg


The modifications  :
On both boards (85052 and 85152) :
-Remove the 2 resistors marked red . (R40 and  R62) (edit : R40 doesn't need to be removed)
-Tap off the audio signal at point 3. (use the pad of the just removed resistor R62 that’s connected to RV5). This goes to the 47K resistors of the GSSL board (shown below in the GSSL  board layout).
- Lift leg 3 of IC5, so it’s disconnected from 0v. The CV comes in at this point, so, solder a wire to it, and connect this to point 4 shown below in the GSSL boardlayout.


The GSSL board :
Only the components needed are shown here. Plus the gain make up pot of course !
A few notes :
-the 0v connection is not shown, but of course, it’s needed also. I don’t need to tell where to connect this, right ?
-Jumper the 2 resistors marked “2”.
-Replace the 2 resistors marked “1” with 4K7 resistors.
3 is where the audio left and right come in from the 552 boards,
4 is where the CV comes from, that go to the IC5 opamps on both 552 boards.
gsslpcbmodification.jpg


I guess that covers it……..
Of course, you can add the Turbo board from Expat to it, which is recommended , and also the SSC boards can be used with it.  The wiring procedure for adding these boards, are the same as it would be for the normal GSSL.

Here a few pictures of the experiment. More to come !:




----------------------------------------------------------------------------------------------------------------------------------------------------------
Addition april 15th 2013 :
I've got some additional info : It's possible to power the 552 from the GSSL board.
The post VCA send will be the output of the module.
The following things will be removed :
the external input, and the post VCA circuitry including tone and TB insert, and mono output.

There are just a few simple things that need to be done to the 552 boards , then it's possible to take out the logic part, so you won't be needing the -25v line anymore.

That means, that you can use the GSSL +/-15 volt PSU part for powering the 552 module, by changing the 7815 and 7915 to 7818 and 7918 (and use a transformer with a dual 18v secondary.)


Here's how to do it :

The mods must be made on both boards.
Summing stage :
-remove TR1, TR3, TR7, and TR9.
-remove TR2 and TR4, jumper source to drain. (pins 2 and 1).

That’s easy, huh ?

Stuff that’s not in use, best is to take them out to reduce powerconsumption. Except for a few hybrid chips, all are socketed:
T85052 board :
Hybrid chips : H6, H7, H8 , H9, H10, H11, H12
Demux chips : IC 7, 8,9,10,11,12,13, 14, 17,

Plus on the T85152 board :
Audio chips : IC 7,8,9, 15, 16
Hybrid chips :  H6, H7, H8, H9, H10, H11, H12 (H7 and H10 are soldered, you don't necessarily have to take them out).
Logic chips : IC 10, 11, 12, 13, 14.
The audiobalancing chips are valuable, so, keep them as spare. (85501 and 85502). The other hybrids are practically worthless.

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Addition June 26th 2013 :
Pictures of a finished Gyraf modified SL552 unit  (without the summing resistor network though) :



and


 

mrclunk

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Your a very generous and helpful chap!
Thanks

Also the -24v rail is just for logic so doesn't need to be regulated.
So u could just tap off the -24v (ish) after the bridge and filter caps of your psu if using a 18-0-18vac transformer.
None other than  ssltech wrote this somewhere on the interwebs i believe...
 

SSLtech

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mrclunk said:
Also the -24v rail is just for logic so doesn't need to be regulated.
So u could just tap off the -24v (ish) after the bridge and filter caps of your psu if using a 18-0-18vac transformer.
None other than  ssltech wrote this somewhere on the interwebs i believe...

That's certainly how I did it when I racked up my 5000 series stuff.

Keith
 

kante1603

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Wow Paul-that´s great,thank you very much for the description!
I´ve got some of these modules(except for all the others),so maybe I can bring them back to life one day ;)

Best,

Udo.
 

kante1603

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Paul,

I have got three questions:

1)Can you tell me the approximate current drawn by the module?

2)How did you connect the Fader;I guess it´s the original console fader,right?If so i will have them somewhere laying arround here.
I cannot remember exactly but it was something like press "select fader" on the IMO and then on the fader module or so to get them working (it is sooooo long ago.... :D).So how is it connected/where does it get it´s DC for the VCA?

3)How did you ground the summing inputs;AES48 (grounds to chassis directly) or different or leave them open?

Thank you in advance,

Udo.
 

helterbelter

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kante1603 said:
Paul,

I have got three questions:

1)Can you tell me the approximate current drawn by the module?

I have no idea....

kante1603 said:
2)How did you connect the Fader;I guess it´s the original console fader,right?If so i will have them somewhere laying arround here.
I cannot remember exactly but it was something like press "select fader" on the IMO and then on the fader module or so to get them working (it is sooooo long ago.... :D).So how is it connected/where does it get it´s DC for the VCA?

The fader as shown in my summingbox is just a 10kLin fader wired to a switch on the rear of the enclosure. This switch selectes either the pot on the front or the externally connected fader. It's not a 506/508/556/558 fadermodule.

You could connect a fadermodule to the 552, but this doesn't really make sense, because the pot on the front of the IMO acts and reacts just like the fader. However, if you want to use a fadermodule, use a 506 or a 508, jumper the computersend to return on the fadermodule (din108: 13a  to 13c)  , and connect the dc output (din108 pin 11a) to the dc input 31B on DIN52. Also make the proper psu connections, and link the masterreset pin via a 10K resistor to the -25v line.

The procedure you mention by the way, is for use with a virtual group fader (SL556). With a 506 or a 508 the fader works directly.

But still, If you want to add an external fader, I'd choose to use just a 10kLin fader, wired directly to the frontpanelpot. Much easier. And you could use a flat Alps of 4 euro instead, making it "desktop style", so you can place it aside to your computerkeyboard. 

kante1603 said:
3)How did you ground the summing inputs;AES48 (grounds to chassis directly) or different or leave them open?

Thank you in advance,

Udo.

I have connected them to the chassis myself, IIRC with a switchable rc filter, but yes, you can leave them open as well.
 

kante1603

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Thank you Paul!

Will do a search in our cellar storage,must be arround 100 5k modules there,maybe even all schemos.
We had IIRC 8 IMOs in our first console so they must be there somewhere... :D
A nice little project for the summer holidays indeed.

Best regards from germany,

Udo.
 

helterbelter

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Ah, cool. In case you come across a pair of SL527 and a few SL523's, I'm interested.  :) I could also use an sl553 for auxes 3 and 4.

by the way, you can use an SL543 (stereo aux master) as a summing amp as well. It has the same circuitry for the summing part, but the features are a bit different : Summingstage>balanced insert>rotary fader > output.  And, it uses LM394's instead of MAT02's for summing. a dual mono aux master SL553 can be used also of course.
 

kante1603

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helterbelter said:
Ah, cool. In case you come across a pair of SL527 and a few SL523's, I'm interested.   :) I could also use an sl553 for auxes 3 and 4.

by the way, you can use an SL543 (stereo aux master) as a summing amp as well. It has the same circuitry for the summing part, but the features are a bit different : Summingstage>balanced insert>rotary fader > output.  And, it uses LM394's instead of MAT02's for summing. a dual mono aux master SL553 can be used also of course.

Hi Paul,

nice to hear there are even more possibilities!
It will take a while to sort your needs out in that mentioned cellar because I have a lot of work at the moment,but I will have a look for you.Cannot state exactly how many of which modules I have,must do some climbing on the top row of a very high storage rack.
The console was replaced by an other bigger one and was at end of days (too much service costs because of lots of trouble with the TR stuff,but the audio part was excellent and fully serviced by Pete Farley himself!).That was at end of the 80s;the console was built in 1987.I was allowed to pull out as many modules as I wanted within a couple of hours because it went to the garbage dump then.Therefore I don´t have any psu,computer stuff,the frame or backplanes-just modules from the top.But these are mine,hahaha!
Will try to find old photographs of it-maybe you can identify some of the modules you want.It was a small console of 24 mono channels (no stereos as far as I can remember) and 8 IMOs,some compressors (4 mono and 1 stereo) etc.Some single modules may have gone as spare/exchange parts for our other console,but most of them should be here.We had the TR module twice as we had a box to remote-control setups,having doubled the "wild faders" in the center section,with built-in intercom and 3 remotes for Studer A812s.

I will post when I am done my "big search" ;)

Cheers,

Udo.

Edit:Some old photographs found and added!
61353363.jpg


77980514.jpg

 

helterbelter

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8x IMO's, but only 2 subgroups ?!?!?..... That is strange in my eyes.

TR trouble...... That doesn't suprise me at all. I don't know the precise reason why SSL stopped the service for 5K's long ago (while they kept servicing 4K's), but I expect this was the reason why. But it's good to know the audio was working fine. I'm always curious for 5K backgrounds, so, thanks for the info !
But, you mention another desk, does that mean you still have a 5K up and running at the studio ? may I ask where ? Is it in Münich ?

I wonder how many 5k's are left intact. There are 150 built in total, I guess there are about 35 left, maybe less.
To list the ones I know of...
1x Swiss
1x UK-Birmingham
2x germany (maybe 3)
1x Australia
1x US (might be getting parted out soon...)
and the one I'm building right now.... In The Netherlands...

But back to your collection of modules : 24 mono channels, then you won't have the 527 or 523 modules (panner and auxmodule for stereo channels). The 543 could be there though.

But this is all off-topic....

 

kante1603

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helterbelter said:
8x IMO's, but only 2 subgroups ?!?!?..... That is strange in my eyes.
Yes,seems strange but made sense :D:The IMOs served our speaker systems-I used the console for live sound reinforcement!!
helterbelter said:
But, you mention another desk, does that mean you still have a 5K up and running at the studio ? may I ask where ? Is it in Münich ?
The desks were located in munich-you´re right."Mine"/ours was the first in germany at the "Prinzregententheater",the second one was bought for a further theatre we where running at that time,the "Cuvillies-Theater"(oldest roccoco theatre in the world).It was identical to the first.Unfortunately it "disappeared" during a long lasting restauration time in the early 90s.At that time I have heard that the Bavarian Broadcast Co. "Bayrischer Rundfunk" was highly interested in buying some of these consoles,but don´t know if they ever did.

Will have a look for the SL543-that´s a stereo-aux module,no?

Cheers,

Udo.




 

DigitalMetal

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Hi Guys,
Im following this thread with great interest, i have a bunch of line modules, Eq's and some 552's on the way to build a 16 channel mini 5K desk using a 552 as the summing amp described in this thread.

Im just trying to sort out a power supply thats big enough to run everything at the moment.

Heres some picture of my parts so far:

28802_436315491200_711511200_5756489_2900625_n.jpg

185740_10150168854951201_711511200_8604256_1097291_n.jpg

207617_10150238961246201_711511200_8947729_1130160_n.jpg

190286_10150166963861201_711511200_8581643_313608_n.jpg


 

kante1603

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DigitalMetal said:
Hi Guys,
Im following this thread with great interest, i have a bunch of line modules, Eq's and some 552's on the way to build a 16 channel mini 5K desk using a 552 as the summing amp described in this thread.

Im just trying to sort out a power supply thats big enough to run everything at the moment.
Hello Neil,

have seen your 5k Psu-Thread.
Nice idea setting up a "small" console,have thought about it too just having a simple mixer without TR or complex routing etc.
Maybe you will start a new thread like "5k small version" or so because there´s one guy who´s naming his thread "my mini ssl" or so.
Would be very interesting for me and maybe Paul would chime in from time to time (as a "Pro").

Cheers,

Udo.
 

helterbelter

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kante1603 said:
The desks were located in munich-you´re right."Mine"/ours was the first in germany at the "Prinzregententheater",the second one was bought for a further theatre we where running at that time,the "Cuvillies-Theater"(oldest roccoco theatre in the world).It was identical to the first.Unfortunately it "disappeared" during a long lasting restauration time in the early 90s.At that time I have heard that the Bavarian Broadcast Co. "Bayrischer Rundfunk" was highly interested in buying some of these consoles,but don´t know if they ever did.

Yes, the Bayern Rundfunk did buy a couple of them. As far as I know, they don't have them anymore. One of them got sold on ebay last year, for just under 7000 euro. ...... an 80 channel, full option console (yes, including 80x 510 and 11x 520 compressors !!!!).

The swiss broadcast company had 3 of them (broadcast versions), they thrown the frames of 2 of them into the scrapheap, sold the remaining one including the modules, psu's and computers to a friend of mine in Zürich, from whom I bought most of my modules, and the PSU. He sold his 5K to another swiss guy, a collector of vintage synths (he doesn't really make music, just a fanatic collector).

kante1603 said:
Will have a look for the SL543-that´s a stereo-aux module,no?
Yes. In the pictures they're located left to the 510 compressors.

 

helterbelter

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DigitalMetal said:
Hi Guys,
Im following this thread with great interest, i have a bunch of line modules, Eq's and some 552's on the way to build a 16 channel mini 5K desk using a 552 as the summing amp described in this thread.

Im just trying to sort out a power supply thats big enough to run everything at the moment.

Hi Digital Metal.

I started my own project 5 years ago with just 3 modules and a JLM kit, and by now my setup can be called a mixer, something similar to yours, but with a few different features.
Not finished yet, but close to completion. I must say that it took me an awful lot of research to get it up and running.

However, your project will be pretty straight forward in case you use the direct outs of the 521 modules. Indeed via 10k resistors into the 552, and you're there. You could use the normal unbalanced output as tapesend. In case you need it balanced, then keith's balancing boards will do the trick.

I've just digged up your PSU thread : http://www.groupdiy.com/index.php?topic=41573.0
I agree with Udo that it would be best to start your own thread for the build that you want to do. I'll try to help you as much as I can, but  must admit that building your own PSU might be a bit daunting.

At a certain point I just bought an original powersupply unit for the console, saving me the hassle of building something powerfull enough for all the modules that I have. Also, it is cheaper to buy something used than to build something decent with new parts. There's also a smaller PSU made by SSL for the 5K series, which is powerfull enough to power your project. It has the transformer, rectifiers and the regulators in a single box. Maybe one will show up at ebay soon. Or maybe Recycled Audio has one. (that's in the UK).
 

DigitalMetal

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Hi Helterbelter and Udo thanks for your help !

Yes i think i will make a separate thread for my build, i wasnt sure if people would get annoyed with multiple threads on the same subject popping up.

Helterbelter, ys how you have described the setup is exactly how i plan to build my project, i have what i believe to be all the wiring info i need and the only thing holding me up is the power supply really.

I have contacted a company in china that make linear dual rail PSU kits to ask if they have an +/- 18VDC version that will run up to about 5 Amps  -i think that should be enough do you?

i am always searching ebay for an SSL Power supply but they never seem to come along, i will get in touch with Recycled Audio how much do you think would be a fair price for a 5K PSU second hand?
 

helterbelter

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Hi Digital Metal,

Since your questions are not really SL552 related anymore, I decided to reply here : http://www.groupdiy.com/index.php?topic=41573.0

You can modify the topictitle if you want to, simply by modifying the first post : subject. This way you have your own "building a 5K" thread. I'll switch on the notificationservice for your thread, and will do my best to help you.
 

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