summing box layout ques

[RANDY]

I want to build a summing box (16 channel like the rolls folcrom but with vol for each channel).Some of the wires comming of the vol pot going to the summing node,are longer than others.Will these channels sound/perform as good as the ones that have shorter wires?THANKS!

[Steve Conner]

Depends.

Do you have unshielded wires running alongside other unshielded wires belonging to other channels?

Did you forget to twist the hot and cold wires of the balanced pairs together?

Do you believe you can hear a difference between different brands of speaker cable?

Have you ever spent more than $5/meter on speaker cable?

If you answered "Yes" to one or more of the above then you may be able to hear a difference in channels with longer wires.

[RANDY]

STEVE, I ANSWERED YES TO ALL OF THE QUESTIONS EXCEPT #2.THIS BOX IS GOING TO BE UNBALACED.I'M GOING TO CHANGE MY LAYOUT AND USE SMALLER POTS.IT'S GOING TO BE A SMALL MIXER!I'M NEW AT BUILDING MIXERS BUT, I HAVE BUILT ONE 8 CHANNEL SUMMING MIXER AND IT SMOKES MY MACKIE! I CANT TURN BACK NOW. (IT'S 4 MONO CHANNELS ,2 STEREO CHANNELS,10K VOL POTS ON EACH CHANNEL, NO PAN(THEY ARE BYPASSED, NOT WIRED IN) , 33K SUMMING RESISTORS,NO 75ohm RESISTOR GOING TO GROUND(LIKE THE ROLLS).I GO FROM THE STEREO OUT TO THE HIGHZ INPUTS OF MY FOCUSRITE ISA428 PREAMPS(DISCRETE PRE'S).THERE IS A HIGH END ROLL OFF AND WHEN I WIRE THE PAN POTS INTO THE MONO CHANNELS THERE IS MORE ROLL OFF.EVEN WITH THE ROLL OFF IT SMOKES THE MACKIE.THE MACKIE SOUNDS CHEAP,BRITTLE AND BRIGHT.THE SUMMING BOX SOUNDS FULL,RICH AND WARM.I JUST WANT TO KEEP BUILDING BETTER MIXERS.ANY INFO WOULD BE GREATLY APPRECIATED.THANKS!!!

[Steve Conner]

You left the summing resistors out? Don't you get a lot of interaction between channels? ie, when you change the level on one channel it affects the others too?

Anyway, if you can hear the difference between speaker cable brands, there is only so much we can help you. You'll just have to experiment and see what you think sounds best, even if that involves crystals and smudging the chassis with incense I run a home studio and I would go insane if I believed for a minute that any of my 100 interconnects and cables affect the sound, outside of the well-known effects like cable capacitance and ground loops.

PS: If you're going to toss out that nasty, cheap, brittle Mackie 1604, give it to me instead, I'll even pay shipping My Soundcraft M12 just died.

PPS: If it has a high end roll off, of course it will sound fuller and warmer and the Mackie will sound brighter and more brittle. Did you consider that the rolloff might be an interaction between the high output impedance of your mixer and whatever the input impedance of the Focusrite pre's is? Adding the summing resistors might fix it by lowering the output impedance.

[RANDY]

Steve,the difference in sound from the summing mixer vs the mackie is more than just hf rolloff. There is a definate improvement in overall sound quality even with the hf rolloff, which isn't too extreme anyway.The sound is richer.There is a pureness to the midrange that the mackie just does not have.I'm not saying it's a neve or a ssl.Just better than the mackie.The speaker cables I think i can hear the difference between where different gauges(way too thin to thick monster cable)so I got the question wrong,sorry. I wasn't able to a/b them so maybe i'm wrong anyway.The input imp. of the focusrite is 1meg.I'm going to experiment with the resistors you suggested.Thanks.

[Steve Conner]

You're going into the Hi-Z instrument input of the Focusrite? OK in that case, I'm probably wrong. That shouldn't load anything enough to cause a rolloff. I thought you were going into the mic input for some reason.

Out of interest, what sources are you mixing with this box? I use a PC with an 8-in, 8-out soundcard for recording, and I always thought I got a better sounding mix if I output individual instruments from the 8 outs, mixed it on the analog mixer and recorded back in as a stereo mix, rather than mixing digitally in my DAW software. So maybe I would like a passive mixer even more...

I'd like to try it, but I'd miss all the other stuff on my mixer like aux sends, mic pres and talkback

[RANDY]

All my inputs are seeing 300ohm coming from an alesis hd24 with external clocking(from a Apogee ad16).There is plenty of gain coming out of the alesis and out of the summing box.The gain knob on the focusrite is near zero!On future mixers I will add sends and /or direct out for effects and add amps/transformers where needed. If i need eq, I insert one between the alesis and mixer but I work real hard during tracking to" get it right" so most tracks dont need eq anyway.For talkback I will use a cheap mic/preamp and go into one of the channels.This is my plan for now but I'm still learning so we'll see.

[RANDY]

By the way, the summing box has a 33k resistor in line from each channel to the summing node but no resistor going to ground from the summing node.The channels dont seem to interact with each other.