[dionvermaes]

Hi!

I'm having a little trouble designing the passive stage of my summing amp, I hope you can help me out!

I need a 16 channel ( 8 x stereo ) passive summing circuit to go into my Capi ACA Board (for the transformers and make-up gain).

I really would like to incorporate a mono switch on each stereo input.

Reading about the ACA circuit I know I'll be using 47k bus resistors on all of the inputs.

1.) What kind of switch should I use to switch 2 inputs to mono ( connect to L and R )?

2.) does this mean I have to place the 47k resistor after the switch?


Thanks!

[Rocinante]

Im gonna help you out here and tell you that you should read everything with the words NYDave summing mixer in it. Also if you scroll down from your post and this you'll see a bunch of posts on it. Best of all there's the search engine above which if you type the keywords you want (LCR, ACA, summing,) will result in providing links with those words in it.

[ruffrecords]

Just to be clear, when you operate this mono switch, you want the left and right signals of the stereo channel  to be combined and panned centre?

Cheers

Ian

[dionvermaes]

Hi Ian,

I'm sorry for the confusion.
The layout is as in the link below

http://wiki.diyrecordingequipment.com/wp-content/uploads/2011/12/schematic.png

channel 1 is fixed to the Left output, channel 2 to right. I want the switch to switch them both to Left and Right.

Dion

[ruffrecords]

Hi Ian,

I'm sorry for the confusion.
The layout is as in the link below

http://wiki.diyrecordingequipment.com/wp-content/uploads/2011/12/schematic.png

channel 1 is fixed to the Left output, channel 2 to right. I want the switch to switch them both to Left and Right.

Dion

So the left is fed equally to left and right i.e panned centre and the right is fed equally to left and right i.e. panned centre. Correct?

Cheers

Ian

[dionvermaes]

Yes, exactly. 

[ruffrecords]

OK, here is a link to a schematic of how it is done using my DB25 PCB but the principle is the same for any passive summer. You need a four pole double throw switch.

https://drive.google.com/file/d/0B_n67A1hN3qtSVJmTzJaMXpFSDQ/view?usp=sharing

Cheers

Ian

[dionvermaes]

Thank you Ian!

[JAY X]

Hi!

I have the same problem with unbalanced mono switch.
In any case if the summing resistors are the same value for both L&R channels, the Signal level will double, ¿Right?
Because there is not a center panning law.

Jay x

[ruffrecords]

Hi!

I have the same problem with unbalanced mono switch.
In any case if the summing resistors are the same value for both L&R channels, the Signal level will double, ¿Right?
Because there is not a center panning law.

Jay x

With an unbalanced system you can compensate for the pan law by altering the bus feed resistor values when you engage mono.

Cheers

Ian