SUM8 Build Thread

[Joe Malone]

SUM8 pcb.
POTS are all 10k log either dual for stereo use or dual concentric stacked mono with odd on top. 1,2 3,4 5,6 7,8.



SUM8 BOM Parts list
1 x SUM8 PCB
4 x Dual opamp NE5532A, LM4562, LME49720, etc
2 x 18v Zener Diodes (only needed if using higher power rails or single power rail)
4 x DIP8 IC sockets
2 x right angle IDC 16 pin pcb headers
1 x 3way 5.08mm terminal block
2 x 10R carbon resistors
24 x 10k metal film resistors
16 x 47pF ceramic caps
8 x 1uF 50v mono caps
8 x 100uF 10v Non Polar caps
8 x dual or dual concentric 9mm 10k log pots

[Rocinante]

This is awesome.

[znjamznjam]

Can we get what more info? Shematic and wiring?
Thanks

[znjamznjam]

Hy i have recived pcb.
Can i get more info about this sum:
Which ic is used
Is er mouser or anders part number for 16pin plug and cable
Is there list for parts in this project?
Thanks in advance

[Joe Malone]

Hy i have recived pcb.
Can i get more info about this sum:
Which ic is used
Is er mouser or anders part number for 16pin plug and cable
Is there list for parts in this project?
Thanks in advance

Added SUM8 schematic & BOM to first post
You can use any dual opamp like NE5532A, NE4562, LME49720, OPA2134.

[znjamznjam]

Thanks

[Joe Malone]

A great example of the type of mixer that can be made with AUX8 & SUM8 at the link below

https://www.jlmaudio.com/forum/viewtopic.php?f=2&t=342

[spyder_hobo]

Hey Jim,

I'm working on a small 8 channel mixing circuit based around a few CAPI boards and a few of your boards.
I'm using the SUM8 board as the backbone to my AUX send/return setup.
I have a couple general questions about mods to the SUM8 Circuit to suit my application.
My apologies if these questions are a little basic, my design background is limited.

1. Is it possible to achieve an inverted output on one stereo pair by removing and bypassing an IC and it's associated input resistor?
2. Is it possible to add gain to an amp stage by changing the feedback resistor. Something like 31.6K for a 10db boost?
3. So long as there is the 10K summing resistor before hitting the mix busses, will the inputs tolerate a range of unbalanced sources? I plan on keeping the aux sends and returns unbalanced and somewhere in the consumer line level gain range for use with reverb echo etc. (Maybe even a couple pedals) 4. Will not using the balancing boards cause me grief?

Thanks in advance for your help, as always, it's much appreciated.

-Stacy

[Joe Malone]

Hey Joe,

1. Is it possible to achieve an inverted output on one stereo pair by removing and bypassing an IC and it's associated input resistor?

Yes each summing stage has an invert stage to return it to same output phase. So if you bypass the invert stage you will be 180 degree out of phase.

2. Is it possible to add gain to an amp stage by changing the feedback resistor. Something like 31.6K for a 10db boost?

Yes correct. Change the summing stage negative feedback resistor to larger to add gain

3. So long as there is the 10K summing resistor before hitting the mix busses, will the inputs tolerate a range of unbalanced sources? I plan on keeping the aux sends and returns unbalanced and somewhere in the consumer line level gain range for use with reverb echo etc. (Maybe even a couple pedals)

Yes the unbalanced inputs are passive 10k log pots so can handle any input level without overload just by adjusting the input pot to the level you need

4. Will not using the balancing boards cause me grief?

The Palpigrade balanced input kit is active so can be overloaded but can handle +26dBu if run on +/-18v so really is no different as it will handle all balanced and unblanced level below that. Again set the input pot to get the output level you need otherwise the overload will be in the summing amp.

[JakeRuben]

Do I need to use the Aux 8 with the sum8? I dont need any control over the input signal. I will be using this to expand the bussing on a console so ideally I would be able to send from the channels of the console to the sum8 via Palpigrade and out Tardigrade then off to the patchbay.

[Joe Malone]

Do I need to use the Aux 8 with the sum8? I don't need any control over the input signal. I will be using this to expand the bussing on a console so ideally I would be able to send from the channels of the console to the sum8 via Palpigrade and out Tardigrade then off to the patchbay.

Hi Jake
If you use a palpigrade it will need 10k resistors in series going to the SUM8 and then the sum8 can plug into the tradigrade fine. But this will just give you an 8 into 8 in output but no actual summing unless you are running multiple palpigrade outputs with 10k summed together on one sum8 input.

Can you let me know how many channels you want to sum to how many outputs? Like 8 stereo inputs to 1 stereo balanced output.

I do have a Stereobus pcb here that can do 8 x stereo input to 1 stereo output that I am about to release which we use for different projects. See attached.

[JakeRuben]

Do I need to use the Aux 8 with the sum8? I don't need any control over the input signal. I will be using this to expand the bussing on a console so ideally I would be able to send from the channels of the console to the sum8 via Palpigrade and out Tardigrade then off to the patchbay.

Hi Jake
If you use a palpigrade it will need 10k resistors in series going to the SUM8 and then the sum8 can plug into the tradigrade fine. But this will just give you an 8 into 8 in output but no actual summing unless you are running multiple palpigrade outputs with 10k summed together on one sum8 input.

Can you let me know how many channels you want to sum to how many outputs? Like 8 stereo inputs to 1 stereo balanced output.

I do have a Stereobus pcb here that can do 8 x stereo input to 1 stereo output that I am about to release which we use for different projects. See attached.

32 channel console with 8 busses. Each buss needs to be summed, which Im hoping the sum8 or stereo bus will do, then each summed bus needs to be sent to the patchbay. So I could have up to 32 channels sending signal to 1 mono buss.

[Joe Malone]

Do I need to use the Aux 8 with the sum8? I don't need any control over the input signal. I will be using this to expand the bussing on a console so ideally I would be able to send from the channels of the console to the sum8 via Palpigrade and out Tardigrade then off to the patchbay.

Hi Jake
If you use a palpigrade it will need 10k resistors in series going to the SUM8 and then the sum8 can plug into the tradigrade fine. But this will just give you an 8 into 8 in output but no actual summing unless you are running multiple palpigrade outputs with 10k summed together on one sum8 input.

Can you let me know how many channels you want to sum to how many outputs? Like 8 stereo inputs to 1 stereo balanced output.

I do have a Stereobus pcb here that can do 8 x stereo input to 1 stereo output that I am about to release which we use for different projects. See attached.

32 channel console with 8 busses. Each buss needs to be summed, which Im hoping the sum8 or stereo bus will do, then each summed bus needs to be sent to the patchbay. So I could have up to 32 channels sending signal to 1 mono buss.

How do you plan to select which of the 8 balanced buss outputs from the console goes to the new 8 buss outputs from the sum8. Sounds like the 8 x 8 matrix mix like the AUX8 does with pot but maybe with switches?

[JakeRuben]

Hi Jake
If you use a palpigrade it will need 10k resistors in series going to the SUM8 and then the sum8 can plug into the tradigrade fine. But this will just give you an 8 into 8 in output but no actual summing unless you are running multiple palpigrade outputs with 10k summed together on one sum8 input.

Can you let me know how many channels you want to sum to how many outputs? Like 8 stereo inputs to 1 stereo balanced output.

I do have a Stereobus pcb here that can do 8 x stereo input to 1 stereo output that I am about to release which we use for different projects. See attached.

32 channel console with 8 busses. Each buss needs to be summed, which Im hoping the sum8 or stereo bus will do, then each summed bus needs to be sent to the patchbay. So I could have up to 32 channels sending signal to 1 mono buss.

How do you plan to select which of the 8 balanced buss outputs from the console goes to the new 8 buss outputs from the sum8. Sounds like the 8 x 8 matrix mix like the AUX8 does with pot but maybe with switches?

Yup there are switches on the console that are already working and wired. I need a buffer/driver to get signal to the bay. Yes 8x8 is it. Eventually I would like to do 24x24 but I want to get the 8x8 working first.

Thanks again for shooting this out with me

[Joe Malone]

32 channel console with 8 busses. Each buss needs to be summed, which Im hoping the sum8 or stereo bus will do, then each summed bus needs to be sent to the patchbay. So I could have up to 32 channels sending signal to 1 mono buss.

How do you plan to select which of the 8 balanced buss outputs from the console goes to the new 8 buss outputs from the sum8. Sounds like the 8 x 8 matrix mix like the AUX8 does with pot but maybe with switches?

Yup there are switches on the console that are already working and wired. I need a buffer/driver to get signal to the bay. Yes 8x8 is it. Eventually I would like to do 24x24 but I want to get the 8x8 working first.

Thanks again for shooting this out with me

Ok still confused. Is there a schematic for the buss/groups or let me know the desk model so I can see photos of the buss switching and outputs?