moamps

"MULT" on SSL patchbays
« on: March 13, 2019, 06:55:01 AM »
In a video tutorial about SSL patchbays an engineer connects two 1176LN outputs to a single mult on the patchbay. Does it mean that SSL uses some sort of passive mixing on MULT or he did it wrong because the two outputs are connected together?
Video is here
https://theproaudiofiles.com/video/how-to-record-lesson-16-patchbays/
at 27:30.
« Last Edit: March 13, 2019, 05:39:41 PM by moamps »


gyraf

Re: "MULT" on SSL patcbays
« Reply #1 on: March 13, 2019, 07:39:11 AM »
ssl mults are just parallels - strange and borderline abusive to use them to mix..

Jakob E.
..note to self: don't let Harman run your company..

JohnRoberts

Re: "MULT" on SSL patcbays
« Reply #2 on: March 13, 2019, 09:48:55 AM »
Well designed gear will tolerate a short circuit on their output by using some series output resistance.

A hard mult can form a passive sum between these two output resistors if the drivers don't run out of current (i.e. might distort on loud passages).

This is not a good practice.

JR
John Roberts
http://circularscience.com
Tune it, or don't play it...

pucho812

Re: "MULT" on SSL patcbays
« Reply #3 on: March 13, 2019, 10:46:18 AM »
I installed that console in that room at that place. before the duality,  it had an ssl4000 which I also installed. I did the entire school along side the other tech there.
You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is.

squarewave

Re: "MULT" on SSL patcbays
« Reply #4 on: March 13, 2019, 11:50:09 AM »
No, the patchbay is just wired in an unconventional way. You can see the patchbay reads "1176 In" on the top row and "1176 Out" on the bottom. Usually outs are on top and ins are on the bottom.

pucho812

Re: "MULT" on SSL patcbays
« Reply #5 on: March 13, 2019, 12:39:24 PM »
No, the patchbay is just wired in an unconventional way. You can see the patchbay reads "1176 In" on the top row and "1176 Out" on the bottom. Usually outs are on top and ins are on the bottom.
Not on the outboard fx rows.

to be more specific... in a typical pro studio you have the following: mic lines to mic pres as a full normal between the patch points. The rest minus the outboard gear  is usually a half normal.  The outboard gear patch points are open, no normal. There will be some exceptions but that is the rule of thumb.  From there rule of thumb is out on the top row in on the bottom row. So output of the multitrack on the top row, input of the line inputs or tape monitors on the bottom row and so on. There is an exception here as well and that is the outboard gear rows which are usually input on the top row and output on the bottom row.  That's the usual in studios. 
« Last Edit: March 13, 2019, 01:27:14 PM by pucho812 »
You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is.

squarewave

Re: "MULT" on SSL patcbays
« Reply #6 on: March 13, 2019, 01:43:17 PM »
From there rule of thumb is out on the top row in on the bottom row. .... There is an exception here as well and that is the outboard gear rows which are usually input on the top row and output on the bottom row.  That's the usual in studios.
Ok. Didn't know that. Thanks.

But just to be clear about the original question, outputs are NOT being shorted through the mult in that video. Only one output is connected to the mult. The other connections are to inputs. So the mult is just being used to split the signal.
« Last Edit: March 13, 2019, 09:33:30 PM by squarewave »

pucho812

Re: "MULT" on SSL patcbays
« Reply #7 on: March 13, 2019, 01:50:10 PM »
Ok. Didn't know that. Thanks.

But just to be clear about the original question, outputs are NOT being shorted through the mult in that video. Only one output is connected to the mult. The other connections are to inputs. So the mult is just being used to split the signal.

from the video at the 27 minute or so mark he is doing a few things. First he is taking his signal and running it into mult #1. I say #1 as he ends up using 2 x mults.  it's a parallel split which he then takes that signal and connects it into the inputs of an 1176(A machine) and 1176(b machine), so 2 separate 1176's. From there he takes the output of 1176(A machine) and connects it to mult #2.  Next he takes the output of 1176(b machine) and connects it into mult #2. so two outputs from two separate 1176's are going into mult #2. After that he takes a patch cable and connects mult #2 back into a line input on the SSL duality.   Effectively  he is trying to passively sum the outputs of the 1176's but as mentioned previously it's not a wise idea  as the SSL mults are just jacks wired in parallel to spit the signal and you may have many issues from distortion to short  circuit of the 1176 output. There are better ways to passively sum these signals.  Warren knows better or at least I have been told he knows better. Many of us in L.A. where he is located are baffled by his statements in the video.
You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is.

moamps

Re: "MULT" on SSL patcbays
« Reply #8 on: March 13, 2019, 06:04:59 PM »
Thank you all for replies.
I teach my students that paralleling outputs is a big mistake, and then one asked me to comment this video.
I replied to him that I believe there is only a one possibility when it can work but not optimally, when two 600 ohms outputs (without feedback coils) are paralleled and routed to a device with mid-high input impedance. Of course, if I assume that the mult is the same as parallel what I believe in last few decades.


squarewave

Re: "MULT" on SSL patcbays
« Reply #9 on: March 13, 2019, 09:33:06 PM »
so two outputs from two separate 1176's are going into mult #2.
Whoops! You're right. I didn't watch the whole thing carefully. He is driving outputs together.


sodderboy

Re: "MULT" on SSL patchbays
« Reply #10 on: March 13, 2019, 09:54:02 PM »
The gentlemanly way to do it is to create summing strips on a bay, same way “passive summing mixers” are made with resistors.  2 or 3 in to one out wired to DL, Dsub, or right to the bay is what I’ve done for decades. It is a winner in situations like this as it saves channels/buses. Hi
Slamping two outputs together with a hard mult probably creates a “unique sound” that is personally desirable.  Better done with trafos than with electronically balanced I would imagine.
Mike

abbey road d enfer

Re: "MULT" on SSL patchbays
« Reply #11 on: March 17, 2019, 03:09:14 AM »
I agree it's "borderline abusive" and "not a good practice", however, since the two ouput stages are identical, the response is more or less intact. Regarding the risks of overloading the output stages, this is probably minimized by the fact both signals are likely to be similar.
Finally, if it sounds good, it is good.
This is something someone with extensive experience can pull out, but I would not recommend that to a noob.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

squarewave

Re: "MULT" on SSL patchbays
« Reply #12 on: March 17, 2019, 07:08:21 PM »
The gentlemanly way to do it is to create summing strips on a bay, same way “passive summing mixers” are made with resistors.  2 or 3 in to one out wired to DL, Dsub, or right to the bay is what I’ve done for decades. It is a winner in situations like this as it saves channels/buses.
I'm due for a patchbay re-wiring session. I was thinking about doing something like this:



[updated version 3]
« Last Edit: March 18, 2019, 11:51:24 AM by squarewave »

abbey road d enfer

Re: "MULT" on SSL patchbays
« Reply #13 on: March 17, 2019, 07:17:21 PM »
You don't need R1 & 2.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

squarewave

Re: "MULT" on SSL patchbays
« Reply #14 on: March 17, 2019, 08:11:53 PM »
Good point. And it drops the output impedance by a lot. Schematic updated in previous post.

JohnRoberts

Re: "MULT" on SSL patchbays
« Reply #15 on: March 17, 2019, 08:12:42 PM »
I'm due for a patchbay re-wiring session. I was thinking about doing something like this:


It's been a while since I did a patch bay (over 3 decades) but I think I came up with a simple mix feature back when.

Each input point had a 1.5-2k (?) resistor between input and normal out. The R was not so much impedance that you couldn't use it as a normal thru patch point.

Then I had a few mults in groups of three or four.  If you want to sum a couple sources patch their normal outs (with build out R)  into the same mult... To combine even more just jumper two (or more) mults together.

FWIW back 30 years ago we didn't sum a lot of sources together passively but a few in the bay was a useful extra feature.

Admittedly my memory about this is more than little fuzzy, I just sketched up something crude and someone else confirmed that it worked and made it happen.

JR
John Roberts
http://circularscience.com
Tune it, or don't play it...

moamps

Re: "MULT" on SSL patchbays
« Reply #16 on: March 18, 2019, 04:41:47 AM »
.... since the two ouput stages are identical, the response is more or less intact. Regarding the risks of overloading the output stages, this is probably minimized by the fact both signals are likely to be similar.....
....Finally, if it sounds good, it is good..
I disagree. Chasing a good sound with paralleling compressors outputs in the situation where you have Duality in hands is stupid, IMO.

The author missed to warn watchers of video that this what he did isn't usual procedure. Also he missed to explain patchbay normalling  what's essential. It looks that he doesn't know much about it.
I found few more videos from the same author, about sound and microphones, and  watching it was a waste of time. Maybe he is good producer but he shouldn't do any technical explanations. I believe, for example, that the member pucho812 can do that 10 times better.

abbey road d enfer

Re: "MULT" on SSL patchbays
« Reply #17 on: March 18, 2019, 07:15:13 AM »
I disagree. Chasing a good sound with paralleling compressors outputs in the situation where you have Duality in hands is stupid, IMO.
Please note that I certainly didn't recommend this, particularly for the less technically versed. I just said that in that case (two identical output stages delivering similar signals) it was a minor issue in most cases. I certainly would not recommend strapping the outputs of two different units carrying two different signals, or would I?
Isn't it quite usual to connect two microphones in parallels when running out of inputs? I mean it's better than having to say "Sorry Bruce Springsteen kid, I'm out of inputs, you can't have Bob Dylan your pal sitting with you".  ;)
Now I agree that there is little justification to do that when you have a large mixer at hand.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

moamps

Re: "MULT" on SSL patchbays
« Reply #18 on: March 18, 2019, 08:25:11 AM »
Isn't it quite usual to connect two microphones in parallels when running out of inputs? I mean it's better than having to say "Sorry Bruce Springsteen kid, I'm out of inputs, you can't have Bob Dylan your pal sitting with you".  ;)

You should take one from a drummer.  :) Hi always has too many mikes around.
It reminded me to one situation I saw where the local government TV did broadcast of live concert of symphonic orchestra. They used to use a stageboxes 4 to 1 or such and expensive mikes (DPA, IIRC) paralleled for "grouping" similar performers. The lack of knowledge and indolence at maximum.
« Last Edit: March 18, 2019, 08:29:06 AM by moamps »

abbey road d enfer

Re: "MULT" on SSL patchbays
« Reply #19 on: March 18, 2019, 08:44:19 AM »
It reminded me to one situation I saw where the local government TV did broadcast of live concert of symphonic orchestra. They used to use a stageboxes 4 to 1 or such and expensive mikes (DPA, IIRC) paralleled for "grouping" similar performers.
Is it so wrong? Typically this type of mics has an output stage with an output impedance of a few ohms feeding the output via resistors that are dominant. Indeed, such a practice reduces headroom and S/N, but, as long as the mics are not submitted to outrageous SPL, it works (somewhat).

Quote
The lack of knowledge and indolence at maximum.
Really? I would think it's a matter of resources. Equipment availability, transportation, crew, set-up time...
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.


 

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