SSlmixed.com Forum
Tech discussion => 4K,6K,8K Series => Topic started by: xmax on April 09, 2015, 03:33:49 PM
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Ok, who here can explain the differences in the way the summing changed over the duration
of these 3 models of 4K's. I have heard G or G+ is balanced, but looking at the documents
that does not make sense. Can modules from a E work in a G or G+ or vice versa?
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For and E to work in a G it needs to have the Coat Hanger Mod, most after 1985 have this as stock, and you have a little jumper that shorts the mod to make it standard E.
I think the G and G+ are quasi balanced., in terms of the summing input.
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I'm not familiar with the coat hanger mod, please elaborate.
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Hi it’s easier to quote SSLtech (Keith):
“The BIG changes to this card were brought about when SSL was being asked to supply ever-larger consoles. -From 40channels being considered 'big' in the early days, to 64 channels being considered unremarkable... the summing buses (which extend the full length of the console) were struggling to sum the signals quietly in larger frame consoles. The original, asymmetrical (single-bus, also called 'unbalanced') summing system was really being asked to do too much, and couldn't cancel induced noise to which a longer set of buses (32 track uses, six aux/cue buses, four or six master buses), and induced noise was becoming a big worry. There wasn't the ability to go balanced, because that would mean replacing every frame mother board, every routing matrix switch, and every CHANNEL mother board... clearly out of the question.
As a result, in the later 1980's SSL switched from the 'unbalanced' design to a 'quasi-balanced' design, where a convenient set of spare pins (which had been grounded for inter-channel separation) were turned into ground-compensated audio ground returns, which would then allow any induced noise to be canceled. -a few retro-fittable changes to the module, one new mother board per bucket, and some modifications to the channel amplifier card, and the hum was reduced. In smaller frame consoles, there was little need to do this mod, but all consoles from about 1988 onwards were made to the 'quasi-balanced' spec.”
(http://i44.photobucket.com/albums/f23/sin-tech/IMG_7408_zpsi5jvc2yp.jpg) (http://s44.photobucket.com/user/sin-tech/media/IMG_7408_zpsi5jvc2yp.jpg.html)
(http://i44.photobucket.com/albums/f23/sin-tech/IMG_7407_zpsytzi09xd.jpg) (http://s44.photobucket.com/user/sin-tech/media/IMG_7407_zpsytzi09xd.jpg.html)
(http://i44.photobucket.com/albums/f23/sin-tech/IMG_7406_zpssafwxbop.jpg) (http://s44.photobucket.com/user/sin-tech/media/IMG_7406_zpssafwxbop.jpg.html)
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great info Andy! ;)
you can start writing an SSL encyclopedia! ;)
Thanks!
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great info Andy! ;)
you can start writing an SSL encyclopedia! ;)
Thanks!
The info is from Keith 'SSLtech' as quoted.
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Awesome Thanks! Both of you! N
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So when you say "one new mother board per bucket" does that mean you have to change one of
the bucket mother boards? Also what happens if you use a un-modded E module in a G desk
or G 26 card? Thanks! N
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I think on a small console, you could keep the bus unbalanced with out issue.
Mine is 32ch, and it's unbalanced bus cards with a mixture of E, G and G+ channels, it's super quiet and sounds amazing.
Think the quasi balanced bus card had maybe resistor packs grafted on.. again could just be shorted, if mixing cards.
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OK, the reason I am asking all this, besides it being awesome to know,
We had one client that was having noise issues with just the E channels
in his mutt SSL (I wish I had a mutt SSL) he had a mix of channels.
He claims only when using the Atomic supply, but than again he never
got back with us. So it might be fine.
The Atomic supply has always been as quiet as the 651's
or substantially quieter, until we ran into this problem.
So I think the main thing I need to know is how to make
the E modules work best with G or G+ 26 card.
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Could you repost these photos?
I'm needing to do this mod and not finding much about it..
Thanks!
v
Hi it’s easier to quote SSLtech (Keith):
“The BIG changes to this card were brought about when SSL was being asked to supply ever-larger consoles. -From 40channels being considered 'big' in the early days, to 64 channels being considered unremarkable... the summing buses (which extend the full length of the console) were struggling to sum the signals quietly in larger frame consoles. The original, asymmetrical (single-bus, also called 'unbalanced') summing system was really being asked to do too much, and couldn't cancel induced noise to which a longer set of buses (32 track uses, six aux/cue buses, four or six master buses), and induced noise was becoming a big worry. There wasn't the ability to go balanced, because that would mean replacing every frame mother board, every routing matrix switch, and every CHANNEL mother board... clearly out of the question.
As a result, in the later 1980's SSL switched from the 'unbalanced' design to a 'quasi-balanced' design, where a convenient set of spare pins (which had been grounded for inter-channel separation) were turned into ground-compensated audio ground returns, which would then allow any induced noise to be canceled. -a few retro-fittable changes to the module, one new mother board per bucket, and some modifications to the channel amplifier card, and the hum was reduced. In smaller frame consoles, there was little need to do this mod, but all consoles from about 1988 onwards were made to the 'quasi-balanced' spec.”
(http://i44.photobucket.com/albums/f23/sin-tech/IMG_7408_zpsi5jvc2yp.jpg) (http://s44.photobucket.com/user/sin-tech/media/IMG_7408_zpsi5jvc2yp.jpg.html)
(http://i44.photobucket.com/albums/f23/sin-tech/IMG_7407_zpsytzi09xd.jpg) (http://s44.photobucket.com/user/sin-tech/media/IMG_7407_zpsytzi09xd.jpg.html)
(http://i44.photobucket.com/albums/f23/sin-tech/IMG_7406_zpssafwxbop.jpg) (http://s44.photobucket.com/user/sin-tech/media/IMG_7406_zpssafwxbop.jpg.html)
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Hi Vancelot. Nice to see your ilk roaming the halls of the forum. Here is a link to more info related to the coat hanger mod etc.
https://groupdiy.com/index.php?topic=24070.0
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I'd like to see the photos as well. can you repost again?
Best,
Roy Hendrickson
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Sounds like making G channels work with a E desk is simply shorting
one of the "balanced" resistors via a jumper. To make E channels work
in a G desk a resistor needs to be added and possibly a fuck ton more.
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What about E desks with their various degrees of Center Section upgrades? Does an E desk with a G upgraded Center require the Hanger mod to use E channels? Or, just truly original G desks? Or, at what degree of upgraded center sections have anything to do with using E channels in an E desk with some form of G center section upgrade? Or does the upgraded center section of an E have anything to do with a TRUE G center section?
Thanks for the help! I hope my post makes sense.
JJ
www.BoogieTracks.com
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Hi,
Sorry JJ, all my fault, I designed the "Hanger" mod in 1985 or 86 (long time ago now!) to fix a huge hum problem we had in the SWF studios in Baden Baden. It's nothing to do with the G series, Paul Frindle and I didn't mess with the bus design when we did the G series tweaks. If you're still having problems and see this message I'll try and remember how it works! I think (and I may be wrong, it's late at night and I've had a couple of glasses of wine :) ) post 1986 channels (E or G) will work in pre 1985 desks, but pre 1985 channels will need a resistor mod to work in post 1986 desks.
It was a real bodge, the 651 (luckily) already had balanced inputs, so I routed the 'cold' side of these, which had just connected to ground, to new "balanced" mix bus "cold" lines, which were just connected with resistors near the channel strips to ground - IIRC some resistors were on the backplane and some on the channel strip. I chose the resistors to give the same equivalent parallel resistance as 8 15k resistors per bay. This basically meant that the 651 was being fed with a balanced busbar (i.e. with the same impedance to ground on both sides) which cancelled out induced magnetic fields. The fact that only one of these buses was being fed with a signal didn't matter.
Hope that helps, message me if you need more and I'll dig my manuals out and remember it in less blurred detail!
Cheers,
Andy Millar
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Adding a resistor to the cold side created equal impedance on both legs,
for true common mode rejection on the buss ribbons?
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Very interesting stuff. Thanks for the info. I've heard of the mod but never truly understood how or why it was needed.
Thanks again!
JJ
www.BoogieTracks.com