A new passive summing box is born, yawn...

Hello all,

Just finished my 3rd DIY project.  I finally built my 8x2 passive summing box.  After reading good things about this subject, I decided I'd give it a whirl.  I inspired myself from Skipwave's unit (OK, let's just use the correct terms here, I shamelessly ripped off his design).  Big thanks goes to NewYorkDave for telling me the correct resistor values!  He's the man.

I built it using no wires at all, just solid copper and resistors...  Here's the obligatory shots:







Now, I brought this thing to the studio yesterday and ran some tests.  Let me explain->  I've got 2 converters hooked up to my RME Digi9652 card, one Apogee AD-8000SE and one ADI-8 PRO.  I normally send my "in-the-box" mix thru the AD-8000SE for monitoring.  Sounds all right.

First, I connected my sum box to my good old RME ADI-8 PRO clocked with Rosendahl Nanosyncs.  Sent it to 2 channels in my Mackie 1402VLZ-PRO just to hear and see if it was working right.  To my big surprise, this combo already sounded better than the in box summing!!!

So I decided I would try the Apogee for outputs instead.  Once again, surprise, I liked the RME better, more transient, more linear (at least to me, this is not a scientific test here, just a first impression!).

Afterwards, I brought up the big pres we got...  I tried a Buzz Audio MA-2.2.  Wow, that sounded damn nice!  It sounded like my computer was going thru a nice console.  Later, I hooked up our trusty McCurdy AU300, now that was a revelation, we flipped...  Double Class-A Tube Pre...  It was the bomb.

Still to come->  My original Neve 1272, a Chandler TG2 and a Millenia HV-3C.

I'll probably print a few seconds of some mix I'm doing these days so we can do a "taste-test".  Now, I've gotta do some more tests to know which converter would I use to print my mix... Apogee or RME?  Stay tuned for the next episode of: That damn summing thing...

Cheers...

Where are the pics, man???

analag

Hey, that's interesting. Your pictures aren't loading, but I'd love to hear some comparison clips.

Oooops, my bad, my server went bezerk for a while... It's back now, I see them.

Got the scum-atic?
:wink:

cor. now that's commando. i dig.

chris.

What's the deal with this? Does the hi quality bus bars play into the sound. I am tempted to start mixing inside the box seeing these.

don't tell m@nster about these they may come out with their own and send the authorities after anyone who makes their own...

Nice. Your's is totally cleaner work than mine.

It sounds like you aren't having any issues, but you are using 4 lug terminal strips, which usually means that one lug is connected to the mounting tab. This could short signal on that wire to ground, which happened to me on my first try. I replaced with 5 lug strips and all was well.

Anyway, good work!

[quote author="guavatone"]What's the deal with this? Does the hi quality bus bars play into the sound. [/quote]

Just by heavy gauge copper wire from the hardware store. I don't think you can do much better than that for conductor.

Hey Skipwave,

Thanks for the "inspiration" man, I realized that I could build that thing quite easily when I saw your pictures.

As for shorts with the terminal strips, I thought about it. That's why I used glue for holding them. I used the "No-Nails" type of glue, let it dry for 24 hours and the next day I checked for shorts with my tester, I was OK! (Fortunatly!)

The copper I used is a simple "house ground" wire that I bought at the local hardware store. Like, 2 feet for not even a dollar and I had plenty, the house ground have like 8 or 10 wires twisted together so, 2 X 10 = 20 feet, I have plently of leftovers too. It's a very good conductor for a low price indeed. I just found out on the net that there's some audiophile places that sells solid silver wire to winding your own transfos and to upgrade your equipment. 20$ a meter for a 0.5mm gauge. Have a look for yourself.

Might be interesting to check it out, I already used 1% Metal film resistors and it sounds quite good to me. I might build a second unit with 16 inputs and switches for left/right.

Thanks for kind words, cheers!

Have you tried inserting analog comps/eq over the pairs coming out of your comp? When I built my passive mixer, I found doing that made a much bigger difference than just the passive mixing part of it. Part of this was because of the bleed between channels. It really made the mix more than the sum of its parts.



M@

Hey Matt,

Yes I did try to put a compressor at the end of my chain. I patched my GSSL compressor after my Buzz Audio preamp. Sounded quite nice I must say. Though, I had to watch it, it was really easy to go on the "overcompressed" land. I think I might need to calibrate my GSSL, I've read a few pages on this issue. Then again, that's another story.

Love the simplicity of construction and look , almost the classic phrase
stright wire with gain , Bravo ! to you and skipw & Dave

what resister values di you use ?

regards Greg

I'm preparing to build a 16 channel version with switches.

I can't decide if I should use the open copper wire method like you've done here, or conventional wire which creates a bit of spaghetti but might make shorter paths and exact junction point clusters.

Anyone have any thoughts if either is better?

cheers.

[quote author="Marc Girard"]Thanks for the "inspiration" man, I realized that I could build that thing quite easily when I saw your pictures.[/quote]

And I got inspired after seeing theDug's picture, so the circle of DIY-life continues. :razz:

[quote author="Marc Girard"]As for shorts with the terminal strips, I thought about it. That's why I used glue for holding them. I used the "No-Nails" type of glue, let it dry for 24 hours and the next day I checked for shorts with my tester, I was OK! (Fortunatly!) [/quote]

I see it now, good thinking! Wish I'd though of that beforehand, too many :sam: while DIY'ing. Oh, well. It was a learning experience.

[quote author="Marc Girard"]Hey Matt,

Yes I did try to put a compressor at the end of my chain. I patched my GSSL compressor after my Buzz Audio preamp. Sounded quite nice I must say. Though, I had to watch it, it was really easy to go on the "overcompressed" land. I think I might need to calibrate my GSSL, I've read a few pages on this issue. Then again, that's another story.[/quote]


Actually I meant over the stereo pairs between your D-A and the passive mixer. Like putting your GSSL on the drum 'group' and another comp on the vocal 'group'. I found this to make yet another level of difference, because of the crosstalk I think.


M@

I think you discovered group compression... a lot of mixes are built that way, not necessary by using passive/active summers. If you compress anything with good quality compressors, you'll experience more detail.

If it's not this what you mean, explain plz

Oh no, I was well aware of group compression already. But I found when I just passive mixed the groups together, there was some difference but nothing amazing. But when I started inserting my analog outboard over those groups I started hearing sounds that I knew I could never get in the box.

My passive mixer (build on a patchbay) uses 1k resistors, so there is more crosstalk between channels than most of the ones people are building here. This means a little bit of everything goes through the drum compressor, the vocal compressor etc, a bit like a live recording or crosstalk on multitrack tape. Youd think it wouldnt sound good but it does, in small amounts.


M@

[quote author="mattmoogus"]Actually I meant over the stereo pairs between your D-A and the passive mixer.[/quote]

Matt, I was thinking, Could I use the quasi balanced thing that you guys have with some of the jlm schems, to go from my unbalanced rca outputs in the DA side of my soundcard, to the balanced inputs on my compressors before going to my passive mixer? I could make up some short cables to do this.

Coz that would allow me to build a balanced summing box and use some of my outboard gear as part of the mixdown.

Or is it better to stay unbalanced the whole way? Don't want to degrade the signal if i can. My soundcard lets me choose between +4 and -10 on the outputs even though they're only rca's.

Does an eight channel passive summer make that much difference? Or, can it be attributed to the nice sound of the makeup gain preamps?

I'd be interested in hearing an eight channel passively summed mix compared to an ITB stereo mix through the passive summer.