Yet another passive summing box! (Pics Included)

[Kingston]

looks like a nice and well executed project.

one thing that bothers me about any passive summing:

did anyone ever compare something like this with simple passive attenuator (blind test). Common sense dictates (to me) that if you want preamp coloring on the master bus, a simple passive summing network like this is only going to add 4 times the D/A converter sound (usually a bad thing) with the preamp drive, versus just the preamp drive using an attenuator and signals mixed ITB.

 

[rsandberg]

Marc,

A friend of mine showed me a method to get tose wires really straight.

Clamp one end in a vice and the other end with channel locks. Make sure you have more wire than you need.

Leave the wire slack.

Then, with one quick motion, yank the cable so it goes tight. You might have to practice yanking to get it right...

The final outcome looks great (not that yours doesn't look great the way it is).

Hope this helps,
Rick

 

[shabtek]

very nice MG...inspired me and my budget


KINGSTON, good point about compounding the converter noise, I never cnsidered that...I think that the benefits of dynamic range and less loss outweigh the added noise though...If one mixes ITB then all those streams of digital info are combined into one stream, and much of the info is dropped or truncated or lost...My experience is that the sound really suffers compared to breaking out tracks or stems and combining them in analog.

 

[bitman]

Well Marc, I just built mine. 8 channel stereo balanced.
I also used those terminal strips - good idea, thanks.
And that trick with a vise and drill for straightening the bus wires is the nuts!

Mine looks like yours more or less so I won't post pics.
While the concept is simple, the build was a bit of a PITA and making
16 cables from my two ADA8000s is a bigger PITA.

All I can hope is that it is better than mixing in the box. :wink:

:Ron

 

[bitman]

Oh boy!

Pulls flame suit on.....

I finished the cables today and hooked her up. Set the busses on my daw to route to the summing box and then back into the daw via the ada8000 preamps.

The mix went instantly 3D with depth I have been without since I sold my console and mixed in the box. Punch drums that have been missing too.

I opened the same project but the in the box version and it sucked again.

It cost about 100.00 to do it. cables and all. Oh and I did buy a second
ada8000 but it is worth it if you feel there has just been something missing mixing in a DAW.

:Ron

 

[meestro]

Would it be possible to just use the pre-punched 1u panels from Middle Atlantic? The part is Middle Atlantic Products UNI-1.

Sweetwater's listing for $20:
http://www.sweetwater.com/store/detail/UNi1

It's got 16 laser punches, ready to take any panel-mount jack. I'm not sure how one of these panels would work in conjunction with a chassis, though. Can you get a 1u chassis with no front panel to use this with?

The panel mount jacks are a little more hefty in cost, but might be worth it so you wouldn't have to do any drilling for the jacks.

Also, for the terminal mounts, would 3 quantity of part #866 work?
http://www.oselectronics.com/ose_p113.htm

 

[illacov]

For ultimate snobbery, you can add different sets of transformers and a switch so you can alternate between them!

How about a set of 3? If you get a big enough case (depends on build, mine was done with heavy guage coated wire and resistors instead of the copper network) and enough space you could have a nice choice of flavors! Like Tamura, Cinemag CMOQ2S (steel vibe) and some API style trannies!

You could also have it so you can switch em out!

That's next on my agenda HEHEHEHEHEHEH


My passive unit is 24 channels (8 mono and 8 stereo) down to 2 with Cinemag CMOQ2S before the XLR outs. Loving it. I want another one with 12 stereo channels for 48 channels total.

Peace
Illumination

 

[peters]

Should the resistor values be any different if doing 8 channels down to one (mono, balanced lines)?
Thinking about doing one of these...

thanks.
--Peter

 

[Davo]

Here's a couple links to check out:

http://www.forsselltech.com/downloads/schematics/8chsum_2.pdf
http://www.forsselltech.com/downloads/design_discussions/summing_buss.pdf


cheers,
dave

 

[steppenwolf]

Hi!
Cool project!
I would be very interested in something like this. I looked in the META but most of the schem links seem to be broken.
Would you have the schematic?
I'm playing with the thought of building one of those but in addition of a build in make up gain stage (maybe SRPP followed by a transformer).
Thank you!
Best,
Stefan

 

[Marc Girard]

Wow, an old thread that just don't wanna die!   I'm happy to see that it's still alive after all this time.  I'm also toying with the idea of building another 8 (or 16) summing bus box with an active section for the output.  I might try SSLtech's SSL9K project since it's very transparent I heard and could be an ideal make-up gain amp as it's not too expensive to build.  One thing that'd be fun would be to have a two layer gain pot so that you can simply adjust the gain of your final mix with one knob...    Still thinking about all of this!   Cheers all!

Marc Girard
www.marcgirard.com

 

[tv]

I think you want the "860"-part: "5 Lugs 0 Grounded"
IMHO you want to ground the "ground buss" at connectors, not troughout the whole box. ymmv

Would it be possible to just use the pre-punched 1u panels from Middle Atlantic? The part is Middle Atlantic Products UNI-1.

Sweetwater's listing for $20:
http://www.sweetwater.com/store/detail/UNi1

It's got 16 laser punches, ready to take any panel-mount jack. I'm not sure how one of these panels would work in conjunction with a chassis, though. Can you get a 1u chassis with no front panel to use this with?

The panel mount jacks are a little more hefty in cost, but might be worth it so you wouldn't have to do any drilling for the jacks.

Also, for the terminal mounts, would 3 quantity of part #866 work?
http://www.oselectronics.com/ose_p113.htm

 

[YLab]

Hey Marc,

Just want to be sure about the resistor values and placement.


           + ---------220---------------------l----------- +
input                                                   10k across the main-ouput
           - ---------220---------------------l-----------  -

Does that make sense?

Hub

 

[crisotop]

Beautiful build, I love the bus-bar thing!

christoph

 

[druedger]

Just wanted to chime in here regarding the use of transformers on the output of the passive summed circuit.  If you use a passive input into the transformer, doesn't that present a problem with impedance matching?  I mean technically the input impedance is going to be variable unless you always run the same number of input channels to the transformer.  That should affect the source impedance seen by the transformer and may result in it not having the proper load to drive the output signal to your down stream connected unit.  Am I off base here?  I build both passive and active summing mixers, and my passive unit has an active summing stage to properly load the output trannies so the source impedance seen by them is always the same.  When in full passive mode, however, the signal is always routed directly to the output jacks and never sees the transformers.

 

[Marc Girard]

Hey Marc,

Just want to be sure about the resistor values and placement.


          + ---------220---------------------l----------- +
input                                                    10k across the main-ouput
          - ---------220---------------------l-----------  -

Does that make sense?

Hub

Hey Hub,

I think you got it reversed!   You need the 10Ks to be on at the input and shunt the busses with the 220 ohms.

Here's your updated "drawing":

          + ---------10Kohm---------------------l----------- +
input                                                      220ohm across the main-ouput
          - ---------10Kohm---------------------l-----------  -

Take note that you only have *2* shunts to install, you don't need one on every input!  

Here's how I did it-->

Cheers and Good luck!

Marc Girard
www.marcgirard.com

 

[steppenwolf]

Just a quick question:

Assuming I put in let's say 20dbU on every balanced input, how much level can I expect at the output when combining those signals?
Is there a specific reason for those values? (200 Ohms should be the source impedance...)
Thank you!
Best,
Stefan
(the 10k+10k into 200 Ohms give me a 100:1 ratio or 40db attenuation, right)

 

[livingnote]

Oooh that's really pretty. Reminds me of the way they did it in my ol' Neumann, just took blank copper PCB strips as the "Sammelschiene" (summing line). Nice work, it's kinda reminiscent of the machines in the City of lost Children.

 

[danjpiscina]

so does this thing work in the same way as the folcrom?

http://mercenary.com/rmfo16chpasu.html

these are great, but a little expensive for a passive system.

 

[phatmateo]

Hi Marc!  I built a passive sum box much like yours and am experiencing a low level hum.  I understand that the shunts(220ohms) are to suppress noise/hum, but what is the math behind that number?  I removed the shunts to see the effect and the hum increased by a huge margin.  Can I increase the ohms to maybe solve my hum problem?  Sorry I'm new to this and trying to learn.  Thanks!