16 Channel Passive Summing Mixer using API312's as Outputs

leitrim_lad · Oct 7, 2010

Hey all,

Im new to the world of DIY and I'm interested in building a 16 channel balanced passive summing mixer using my DIY API312's as the outputs. Was thinking about going by the design on forsell's website below

http://www.forsselltech.com/downloads/schematics/8chsum_2.pdf

Dont intend on using any pan or level controls just the simple summing box.

What I'm wondering is about resistor values I would use for the 16 channels and if this will work for me full stop? On the 8 channel version in the example above they use 5k. Will i need to change this for the 16 channels?

Any help would be greatly appreciated..

Cheers

pyjaman · Oct 7, 2010

Hi!
You could look into the META (first or second sticker in " The lab"). There's a mixers meta with loads of infos and theory in there about passive mixer design.
Look for example at NYDave's passive summing network.
Laurent.

leitrim_lad · Oct 7, 2010

Hey Laurent, cheers for the reply. Ya I've looked through all the META and nydaves seems to be the design to go by but i cant find any schematics anywhere for it, all the links seem to be all dead links. Would you have any other info on where to get these?

Cheers

[silent:arts] · Oct 8, 2010

FIGURE 3

syn · Oct 8, 2010

Figure 3 is virtual gnd. summing thing. He needs to use non inverting op amp config for the passive summing. 1.5k-10k will do for the (passive summing) resistors for 16 ch.
Smaller resistor more crosstalk- but less signal loss, larger resistor less crosstalk- more signal loss. You need to find NewYorkDave's schemo.
Cheers
EDIT:
F.F. shemo is having 600r output impedance which API might/might not like. If using mic preamps for gain make up you need output impedance to be around 200r, so that the mixer looks like a mic to a preamp, impedance wise..
EDIT2:
http://www.twin-x.com/groupdiy/albums/userpics/balancedmixnetwork.pdf

leitrim_lad · Oct 11, 2010

Thanks for the reply everyone.. SYN is that NYD's schematic you just posted? If it is THANK YOU SO MUCh.. Couldnt find it anywhere. It was so helpful. Gonna take into this later on now so ill see how I get on..

Cheers