16 to 2 "summer" question

[snaper]

Hi Guys,

Finally, I've managed to build a trolley rack, and I have 1U left, which is ideal for a simple passive summing box.
I'd like to make as simple as possible, but it seems I'll have stereo sources as well. (Sampler)

My question is that do anyone has a schemo for such thing, like 8 stereo inputs, 8 mono inputs and 1 stereo out, but fully passive, without input or pan control?

 

[snaper]

Another question is that is it worth to install transformers to the outputs?
Just for colouring...
Still 'd like to keep it passive :S

 

[Joechris]

You need  some makeup gain after this "summer" so use a preamp or another amp with your favorite transformers..
Look for ruffrecords  posts...

 

[snaper]

Hm...yes, that is my problem.
I'd like to use my soundcards preamp as a makeup, but I think it is a very clean and transparent pre, so I thought it would be great to add some dirt with a transformer after the summing stage, but as I sad, I'd like to keep this thing passive...

 

[ForthMonkey]

If you want to build summing mixer with transformer,you can try Majestic Buzz.It's really easy to build and has DB25 option.I've just built it and i'm really happy with it!

And here is my version for Majestic Buzz.Made with DOA.

http://groupdiy.com/index.php?topic=63926.0

 

[snaper]

ForthMonkey,

Looks amazing, thank you very much, but I could say no for the transformer, cause it has to be passive.
I thought that I could use a transf. in a passive circuit.

 

[snaper]

Another question, I think I forgot to mention, that I don't want to use this summing mixer for summing from DAW, but for summing all of my synths, sampler, etc. into 1 stereo for my soundcard.
The passive mixer shcemos are still OK for this application?

 

[ruffrecords]

Another question, I think I forgot to mention, that I don't want to use this summing mixer for summing from DAW, but for summing all of my synths, sampler, etc. into 1 stereo for my soundcard.
The passive mixer shcemos are still OK for this application?

Do they have  balanced or unbalanced outputs?

Cheers

Ian

 

[snaper]

Do they have  balanced or unbalanced outputs?

Cheers

Ian

Ian, both. On the sampler, I have balanced, everything else is unbalanced.
Tried to find the specification of the outputs, but no mention in the manual.

 

[ruffrecords]

Ian, both. On the sampler, I have balanced, everything else is unbalanced.
Tried to find the specification of the outputs, but no mention in the manual.

OK, that complicates things a bit. I expect your sound card has an unbalanced input?


Cheers

ian

 

[snaper]

OK, that complicates things a bit. I expect your sound card has an unbalanced input?


Cheers

ian

It is an Akai EIE, checked, unbalanced, yes.

 

[ruffrecords]

It is an Akai EIE, checked, unbalanced, yes.

OK, so you have an unbalanced card input, mostly unbalanced sources and one balanced source. On that basis it makes more sense to make your summer unbalanced. Do you want to have a fader for each input or do you just want to sun what comes in?

Cheers

Ian

 

[snaper]

No faders, I can controll the volume and pan on the instruments, so yes, just unbalanced summing.

 

[ruffrecords]

No faders, I can controll the volume and pan on the instruments, so yes, just unbalanced summing.

In that case just make a really simple resistive summer using 10K resistors. Just feed each input in through a 10K resistor and connect all the other ends of the 10Ks together and that is your output. The only problem is the balanced output. Some balanced outputs do not like having their cold output connected to ground. To be on the safe side, leave the cold unconnected and just feed to hot into the 10K resistor.

With this scheme the loss will be equal to the number of inputs. So if you have 6 inputs the loss will be 6 times or just under 16dB. You card line input will need to provide  some gain to make this up.

Cheers

Ian

 

[snaper]

Thank you very much for the help Ian.