DIY Summing Box Completed

We'll its crude and rude but works like a champ, so dont laugh. I built it based off a folcrum using fosseltechs notes. Since people are split pro/con over these I decided it was something easy to try. Other then racking some sweet 1970 Telefunken 372Ds this is my first DIY project from scratch.
I also like the idea of a passive design because I have several sweet preamps to test it on.
I ran this through a API 3124 comming out of a Motu HD192. Initial results were pretty
breathtaking. I read some people said there was a 5% improvement over
mixing ITB, but what I noticed was night and day.
My thoughts were:
Better seperation between instruments, you can really pick out
individual elements in the mix alot more clearer.
Stereo Field is much more wider. ITB mix A/B almost seems more mono and collapsed.
Reverb tails are much more noticeable and present.
More overall punch (this may be a API characterastic)

The only drawback I heard was that I feel some of my low end and
overall power went down somewhat, BUT I took a already finished mix
and sent it through this. So I imagine if I can remix while monitoring
the summing device, which is what I have been told you really need to
do, I can retweak this in the mix. But overall this concept is really
mind blowing compared to ITB summing. And to me it makes all
the sense in the world to let some nice Analog pres do the summing then
the PC do the math. Just my opinion.
I want to try it on my Focusrite RED, Telefunken 372, Avalon 727, and
Neve 1073 and compare results.
If I build one again I will take my time and make it alot more
neater and actually use some Lazertran decals I have, but I was
anxious to hear what it could do.

Todd Matthew Stotler
www.echoesrecording.com

what a nice mess :thumb:

the loss of lowend might come from the fact that your API´s input transformer want to see lower output impedance from the connected device.

steff

whAT THE.... :shock:

Yeah CJ, I know it's a pile of Spagehtti but I am going to rebuild it
more neater. But thanks anyways for putting down someone just starting out doing DIY. I appreicate it. Next I post something I'll make sure
its up to something George Massenburg would put together.

Todd

todd chill.

hang out for a while and get to know the people here, most everyone is really good intentioned.

rebuild it more gooder.

dave

Todd, I used to get annoyed at CJ sometimes until I found out that he used to wash his hands with trichloroethylene. Now I understand and I cut him some slack.

(Just kidding, CJ! :razz: ).

Seriously, though, the very first things I built many years ago didn't look any better than that. Now, I've been building crap for over 25 years and there are some guys here on the Lab (mostly from Europe, mostly younger than me) who build works of art that make my humble efforts look like doggie-doo. We're always learning, always getting better... Congrats to you for putting together something that works; that's the first and most important step!

hey if it sounds good and will be covered up who is going to know. Plus if you want can alwasy clean it up later, It works and sounds good which is most important. :thumb: But you know zip tie are so cheap can get 1000 from frys for 7.00 US gotta love it.

Thanks guys. I apolgise to CJ if I was rude. I was just comming on
wanting to learn how to improve what I was trying to acomplish
and guess I took things the wrong way.
I agree about 'no one will see it' but I want to get into
good wiring pratices now. I was in a rush to get the thing together to hear how it would sound, next time I will defintly take my time and make it
neat.

Todd

I know what this device is - it sums line outputs, but what is actually inside the box? Is there any circuitry, transformers, etc?

Just wondering as I can't really see from the photo.

It'll look fine when you tidy up the cables :razz:

Pucho's idea with the zip-ties is good.

That would make it look betterer.

Todd, I was trying to be a bit humorous there, but I guess it went over like a led balloon. So sorry about that, and no harm intended. I thought Scenaria was trying to pull a fast one. I have to be the sloppiest guy at this forum. And I am trying to improve with each project. Really I am.
I did not see you post tally of 6 before commenting, thus...

Anyway, nothing leaves me colder than a box with a prefabbed pc board, a bunch of opamps, and a real slick front panel. I mean, it probably sounds good, and I plan to build some stuff like that myself pretty soon, but my heart is with a pile of tubes and wires that have been tweaked for low noise and high fidelity.
Witness the following admissions of guilt as I hold my head in shame:




http://vacuumbrain.com/The_Lab/TA/Pultec/meq6.jpg

http://vacuumbrain.com/The_Lab/TA/Pultec/meq10-2.jpg

Feel better now?

Oh yeah, welcome to the Lab!

But the next time you take a pic of a pile of wire in a box, tell us it's real! :grin:
Keep a copy of that pic. In 30 years from know, you will get a kick out of it. No wait, that's how long I have been building, and my stuff still looks like crap. Cancel that last statement.

PS: I have pics of stuff way worse, but even I am afraid to post them. :roll:

Todd,

Welcome to the forum! I am certain that you will find that everyone here is really very encouraging and helpful. CJ included... :razz:

Nice job on the front panel! I will say that I am impressed that you at least chose to use different colors of wire on your box. I am always perplexed as to how someone will troubleshoot a box with a bunch of wires that are all the same color. (Like CJ's!) No insult meant to my DIY bro, CJ! I just know that I would have a LOT of trouble with that myself. I have enough trouble when there are lots of colors.

Peace!
Charlie

Yeah, you definitely can't take CJ too seriously. :razz: We all love him anyway, though. :guinness:

Hey, I say if it works, and works well, then I don't care how it looks. Good job! :thumb:

Nice work on the summing box. Just for clarity, did you build a passive summing box with no set makeup gain in the box? I think you're saying that you plan to use various preamps for makeup gain? If so that's not a bad idea at all, but I think you might have better LF response if you take the output of your summer into a line input rather than a mic input... as Steffen stated. I think your 3124 has line inputs ?!?

Hi Todd,

Welcome aboard! I'm building something quite similar, but prettier :wink: :razz: . How much makeup gain are you using from the AP1 pres? If your M0TU HD192 is like my 896, there are switches on the line outputs for +4/-10 level. The lower setting might be better suited to pre, although this means more gain, more noise, etc. Just a thought. Glad to hear that you like the difference this technique makes. I'm excited to give it a try.

Brian

hi todd,

maybe your wiring makes your box sound unique, wait for a couple of months everybody will do it like that ;-)
think of it like that: the magnetic fields of the strips influence each other, so its better to have this randomly. just a thought...

may i proudly present my first diy, still use it in original design:



(yes, my clients always want to beat down the price after they have seen it...)

Wow, as long as it works and sounds great, we don't care about the wiring!

You almost did exactly want I wanted to try for a while: build a passive summing box that would be small and convinient. I wanted to grab a small Hammond metal box and do the DB-25 on one side and 2 XLRs on the other...

It would be fairly easy to build, just a few wires and I would solder the resistors right on the DB25 connector... So no mess! (Just kidding!)

Welcome to the coolest board on the internet.

Welcome to the nicest board for people like you, Todd!
:shock:
I heard alot of rumours about passive summing boxes round here and everywhere else where people talk about DAW's and pro audio.
This is a pretty cool plastic box - maybe you should look here
http://www.groupdiy.com/index.php?topic=7799&highlight=tupperware+sontec
for inspiration on your next diy project!
Build a plastic highend mastering studio! :green: :thumb:

Best of your box:
Absolutely the same "pure and pristine passive signal path", "no op amps or ICs, no gain or pan controls, and no power supply" and last but not least "no capacitors".
Yes, the F*lcrum is nothing more than a bunch of cables and resistors on the ins, bunched together at four points giving two symmetrical outs (just to tell what's inside this $995 list price box, i didn't saw the insides, just from reading the sales sheet, what else could be inside?). And surely the DB25 connectors version is alot cheaper than your summing box with all that lovely XLR's...
Well, i still have alot of sommer cable laying around here, i could try to throw a box like this together at the weekend WHY NOT :thumb:
I'm sincerely convinced that you could reach better specs than the f*olcrom (Frequency response: 0-500kHz Crosstalk @1kHz: -90dB) because you don't have to deal with frequencies >24kHz (as i don't know much audio DAC which don't filter this stuff out) AND your ins and cables should be better separated as a DB25 connector for less crosstalk (did you perhaps already measure it?). I also saw, your box don't even has a left/right switch, so ONE PROBLEMMAKER LESS :idea: !
Well in the PURE PATH theory you already seem to be superior. Take care of it, customers could come to the conclusion that it is worth to get criminal to have it at home.... :grin:

So, seriously, what resistors do you use? Any fancy? Other values as mentioned here on the board?
Do you get 150 Ohm output impedance and -35dB output like the F*lcrom? This really would be great to reuse micpres....
I LOVE the idea to build a box just like this (having 16 outs from the DAW and a quality stereo standalone mastering DAW)!
If you want to rewire, i would zip up the stereo channels to simulate the standard console usage :wink:
Are there mono channels for center usage implemented (for bassdrum or the like...)?
The simplicity of your unit is by no means "unpro" but inspiring and motivating for us.
I really think i should go for such a project to motivate me building up the micpre pairs that wait for completion (2x Ap*i 312 and 2x green V14) on my workbench...
should be even more rewarding as a GSSL (in terms of time and success, not in terms of sound and complexity...i'm building a GSSL right now myself, nearly finished).

Thanks in advance
and HAPPY DIY :thumb:

Martin

PS: You will get used to CJ's sense of humor very fast after reading a few threads about slaughtering rare and expensive transformers in the name of science... :twisted:

Don't kid yourself that you will sort it out later(if you are anything like me, that is . . . ) i know from experience that as soon as the lid is seeled and it actually WORKS, that's it! A combination of the fact that, as soon as it enters service it "IMMEDIATELY" becomes "ESSENTIAL", and "I CAN'T MIX WITHOUT IT", combined with "AWW, F@@KIT", I'd far sooner start building the NEXT hair-brained, mad-cap, dumb-assed contraption . . . meens that, unless it Fails Due To Poor Build Quality, it is doomed forever, with me hoping that Someone Worthy NEVER gets to see the Abomination that Lurks Within . . .


Or is that just me? :roll:


ANdyP

ps PAssive summing RULES in my book. I have a network built into the patchbay, so I can use any one of my Pre's for make-up. I like my Helioses, especially my API-u-likes (with Neve input trafo's), but surprisingly, Highly recommend our otherwise seldom-used focusr@ites for this. Most surprising, I must say! I seldom if ever use them for anything else. Ho hUm! Finally, they can justify their place in the rack.[/list][/url]

No, andy, you are not the only one...
"yeah, hmm, i will be recapping this thing later with high end electros and polyprop..."
- never changed a single cap...
"A unique sounding single pre..." now.
The first ones are often the best liked. I often build one unit and make a pair afterwards (stereo match) - then call my proto No.1 a "vintage" model...
sounding from reused caps i don't have enough afterwards for a stereo matched pair.....
:grin:
finished a "100% reused component electronic waste from the street / hifi and video dump" green MK 1 and it sounds GREAT (ok, opamps were new, but what i had laying around...MC33078). I even used slightly other values in some places...because i didn't had to order to finish (resisters...).
It works, it sounds, it will NEVER be fiddled around with...if i wanna fiddle i'll build a new one :grin: .( two pcbs on order )

:razz:
That's DIY - YOU make the rules...
(i really get excited about this summing box...)

Martin

So could somebody make a wav recordings of the mix using in-the-box mixing, using the external summing box, and the sum of the ITB mixed and inverted OTB mixed wav's. I would like to know what's the difference actually. My theory is that it's in the impulse response of the gain make-up amplifier... Though it's not so linear that it could simply modelled by sampling the IR it could maybe modelled using some other way (modelling actual circuits in component level like Kjaerhus does their VST's).