DIY Summing Box Completed

Thanks for all the welcome guys. Again sorry CJ if I took you wrong. Your
pictures made me feel alot better :grin:
Yes this unit is fully passive, based from fosseltech (? I belive was the schematic I saw) which was pretty much based from a Folcrum.
The API does have Line inputs but I was using the XLRs which is
what I read the folcrum recomends you to do, I will try the line in's.
My whole intention if this worked was to buy the Folcrum. But seeing that I had all the spare parts lying around and it looked easy to try I decided
to give it a go, I justs didn't belive it was going to work as well as it did. Also I got bit by the DIY bug by racking up some
Telefunken 372Ds.

Todd

Actually, it's more like the Fulcrom is based on the Forsselltech schematics. :wink: Although Roll Music did solve a number of extra problems they encountered.

Fred Forssell hangs out around here, by the way. So does the Roll Music guy.

Good one, Bryson!! :razz: :razz: :razz:

If it sounds good, that's all that matters, right? Good job !

I love seeing projects like these because its very inspiring to see what can be built from spare stuff with the help of our feathered friends. ; )

At some point I hope to offer up an 'opensource' mixer design to be scrutinized and used by the community... but first, to finish the three project DiY builds which make my living room look like a warehouse.

These projects take allot of energy and effort to get going from zero, but once the momentum is there. . .


cheers guys ~
Jay

This stuff isn't anything... wait until you guys see my Sta-Clone.....

What a mess!

Hope It doesn't expolde

Question:

How many tracks are going into the summer?
Are you sending mono tracks to it or stereo pairs for each input?
And are you sending busses or individual tracks to it?

Thanks in advance.

I seriously doubt that it will explode due to the passive nature of the
device but I will keep a eye on it just in case :grin:

The unit is 16 XLR ins and 2 XLRs out, all passive design.
1/4" Metal film resitors, 5 K

I usually send 8 Stereo pairs into this out from my Motu HD 192.

I send sub groups out from the mix, typically I would do something like
this:

Drum Bus Stereo pair one
Bass Bus Stereo pair two
Guitar Bus Stereo pair three
Lead Guitar Bus Stereo pair Four
Vocal Bus Stereo pair Five
Backing Vocal Stereo pair six
Percussion Stereo pair seven
Misc Stereo pair eight

I did a/b tests to in the box and they were night and day in terms of
sound. The clarity and stereo spread really jumps out.

Todd

OK!

Thank you, I was wondering about just this issue when concidering summing boxes. And that was this:

Scince the summing boxes I have seen are not really high I/O counts,
(Many have 8 inputs, yours smartly 16,) I assumed that you and others must be sub-mixing "in the box" then sending the submixes to the analog summer.

I wondered if this could really sound like "night and day" scince some contamination (if you will) of the signal was already done in the daw
while summing up the sub-mixes and we are only sending those pre-summs to the summer, not each track.

You post has given my new hope. As 48 tracks of summing inputs to mix down 24 tracks (and retain daw panorama) was a more soldering than I wanted to do right now :wink:

It appears I can indeed sum 8 sub-mixes and still recieve the benefit of those lowley resistors!

Hot diggity!

:Ron

Pardon my ignorance if the answer to this is obvious....

What is the point of the L/R/Both switches on the Folcrom? Is it so you don't have to repatch if you want to change your routing? It seems that the "standard" way to send audio to the box would be the way Todd describes - as 8 stereo submixes to 16 predefined L or R channels. Is the purpose of the switches to give the option of mono on one channel of the summing bus so you don't have to take up two channels to get mono, as you would with a hardwired L/R/L/R... box?

Thanks.

[quote author="cwileyriser"]Pardon my ignorance if the answer to this is obvious....

What is the point of the L/R/Both switches on the Folcrom? Is it so you don't have to repatch if you want to change your routing? It seems that the "standard" way to send audio to the box would be the way Todd describes - as 8 stereo submixes to 16 predefined L or R channels. Is the purpose of the switches to give the option of mono on one channel of the summing bus so you don't have to take up two channels to get mono, as you would with a hardwired L/R/L/R... box?

Thanks.[/quote]

Simple, really. If you're mix contains mono tracks, they can piped into the passive mix box in mono. I'm in the process of building a balanced box with the 4p3t switches. I want to stretch those 16 inputs as far as they'll go.

Welcome Todd!

Thanks for putting this up here, seems to inspire a lot of lurkies too! :thumb:

If CJ bites again, just toss him a trafo to hack, that what this community did in the beginning days... he's better now, look he even apologized :green:

Humour too CJ :green: !
You know we love you :shock:

Tony

[quote author="JasonWWW"][quote author="cwileyriser"]Pardon my ignorance if the answer to this is obvious....

What is the point of the L/R/Both switches on the Folcrom? Is it so you don't have to repatch if you want to change your routing? It seems that the "standard" way to send audio to the box would be the way Todd describes - as 8 stereo submixes to 16 predefined L or R channels. Is the purpose of the switches to give the option of mono on one channel of the summing bus so you don't have to take up two channels to get mono, as you would with a hardwired L/R/L/R... box?

Thanks.[/quote]

Simple, really. If you're mix contains mono tracks, they can piped into the passive mix box in mono. I'm in the process of building a balanced box with the 4p3t switches. I want to stretch those 16 inputs as far as they'll go.[/quote]

OK, thanks - guess I wasn't as stupid as I thought! :shock:

Out of curiosity - what kind of 4P3T switches are you using? Toggle or rotary switches?

Although I imagined a lot of people sending stereo submixes into the passive box, my own stuff (though not necessarily stuff recorded for others) is rarely more than 8 or 10 tracks mono, one or two stereo tracks and an aux channel or two. So, it'd make a lot more sense for me to have the option of sending mono tracks in one at a time, instead of as part of a stereo submix.

I have wondered about all those switches on the Folcrum myself, thanks for the explanation. I just wanted to build my unit with the cleanest
possible straight path in and out.
After several months mine still works like a champ, even with the
mess of wires inside it sounds awesome on my mixes.
One thing I have noticed is I dont like to pop it on a final mix because it does change some of mix enough to warrant some changes, at least to my ears. I prefer to mix with it during the whole mixdown.
What it does for the stereo field is just mind blowing.

Who exactly came up with this idea anyway? Someone told me Fosseltec did and then Folcrum copied it from him, and so forth. I know the idea is based off of large format analog boards, but I was just curious who had the idea to try this.
I am surpised the chinese havent started mass producing these, exspecially since our patents mean dog crap to them and these are
the big thing right now.

Todd

www.echoesrecording.com

Who exactly came up with this idea anyway?

Click to expand...

The idea of mixing signals in a resistive network is about as old as electronics itself. I have books going back to the '30s that make reference to it, and it was already old news by then. The requirement for mixing goes back at least as far as the 1920s and the advent of sound films.

As for who first thought to build a simple box o' resistors to mix outputs from a DAW, that's a good question. It may have been someone who had to take out a second mortgage to afford his SlowTools rig, and didn't have any money left over to buy a mixer once he realized that the in-the-DAW mixing was somehow lacking.

Although people were building these boxes for their own use for some time, I'm sure the first to market such a box--that is, completely passive and targeted at SlowTools users--was Justin Morse (Folcrom). However, I think the general concept of the stripped-down mixer especially for DAW use might have originated with the Dangerous 2-Buss. Or at least theirs was the first product of that kind I remember seeing.

I know the idea is based off of large format analog boards

Click to expand...

Huh? Well, they both mix signals through resistors. That's about as far as the resemblance goes...

I am surpised the chinese havent started mass producing these, exspecially since our patents mean dog crap to them and these are
the big thing right now.

Click to expand...

Be surprised no longer:

http://www.smproaudio.com/PM8.htm

As for patents on the idea of passive mixing: see my first paragraph. There's nearly a century of "prior art" and I doubt anyone could get a patent on the concept (unless he hired whatever patent attorney works for Randall Smith or Aspen Pittman :wink.

If the SM box was a copy of Folcrom's circuit, or Forssell's, or any of the schematics I posted, it would be annoying but very likely not actionable. The basic concept itself is just too fundamental to be considered novel; all that distinguishes the circuits are details of implementation.

Thanks for all the info Dave. Much appreciative.


Todd

Dave, does it make sense to ad trannies on every input?
I would like to "Edcor" a prototype, any favoured types?

[quote author="tony dB"]Dave, does it make sense to ad trannies on every input?
I would like to "Edcor" a prototype, any favoured types?[/quote]

I used Dave's balancedmixnetwork PDF to make a summing box. I don't think that trannies would offer any improvement. It would save a few resistors, but the cost of the trannies would be far more than the resistors.

Also, the idea of the summing box is the keep the signal path as short and simple as possible. Unless you really wanted the sound of certain transformers, they seem like an unnecessary source of coloration/distortion.

I agree, I think the transformers would be defeating the 'keeping a short and clean path' concept.
I have been toying around with building another one and making it active, possibly using the new That Mic Pre for the make up stage.
I do love though that with a passive you can mix around alot of different pre's.

Todd

www.echoesrecording.com