NYD LCR assign switch & Lorlin trouble.

Hi friends,

As a part of my active summing mixer project,  i am a expanding this summing device with the LCR assign switch designed by New York Dave. (Balanced mixing network pdf)

To build that switch first i numbered each pin in the schematic from top to bottom as 1 to 12.
Then i build the resistors and wires arrangement in a breadboard, so to end with an input (+ -) , four 4k32 resistors, and 12 wires that go to the Lorlin switch connected to the same number pins 1 to 12

In the Lorlin 4P3T, i connected the four central pins to the 22k balanced summing network this way:

A + 1 L
B - 4 L

C + 7 L
D - 10 L

The twelve lorlin pins  i understood they are arranged this way:

1 L  4 L  7 L 10 L
2 C  5 C  8 C 11 C
3 R  6 R  9 R  12 R

When I turn the pot to the right, much of the volume goes to the right , but the left side still can be heard a bit.

At center the volume rises more, as expected.
At left position I can’t hear more volume than in right position.

I think there is something  wrong assigned or the central pins assignement is not correct.
¿Maybe 8 R  and 12 R?

Also I have to say that in my active summing mixer I have a little imbalance between  L and R channels.

Thank you for your help!

JAY X

The schematic shows a passive balanced summing network, so you leave out Rx when connecting to your (not shown) summing amp design.
Pole 'A' connects to 10K summing resistor into bus L+
Pole 'B' connects to 10K summing resistor into bus L-
Pole 'C' connects to 10K summing resistor into bus R+
Pole 'D' connects to 10K summing resistor into bus R-

Input + (in phase) connects to throw 1 and 9 in parallel and in series with (for 10K summing resistors per phase) 4K3 resistors to throw 2 and 8.
Input - (out of phase) connects to throw 4 and 12 in parallel and in series with (for 10K summing resistors per phase) 4K3 resistors to throw 5 and 11.
Throw 3 and 6 are linked for common mode=muting the left bus in switch position 3 (R).
Throw 7 and 10 are linked for common mode=muting the right bus in switch position 1 (L).

Your level jump in center position is probably caused by these 4K3 resistors, which have to increase for 22K (11K per phase) summing resistors.
Level at the opposite L/R side might be caused by missing links at switch throw 3/6 and 7/10.
Imbalance in your active summing amp might be caused by different resistor values in the feedback network.
Good luck

Thank you Harpo,

My summing amp is based on Tim Farrant design, but without transformers.

I will re-check  all connetions, and resistor values.

By now i only have 4k3 and 8k6 resistors.
I will post some pictures asap.

Thanks again,

JAY X

Hi Harpo,

Attached is the breadboard of the assign switch. I revised it and did not found any soldering mistake. also i checked the wiries comming from the summing board and are correctly assigned.

Levels at right and left are simmilar. At center it rises up.

Something is reverse wired:

I turn left and right side volume rises
I turn right and left side volume rises.

ascii schematic of levels:  L C R
          I
I        I        I 
I        I        I
I I      I      I I

JAY X

Throw side of the switch looks OK (for passive summing), but resistor values don't make much sense without knowing the full schematic, as active summing is most often done different (debalancing stage in front, different summing resistors as part of gain setting network in the summing amp and for usual don't need a 4P3T switch for LCR bus assign).

Hi Harpo,

I sent you a PM with the schematic.

JAY X

Hi Harpo,

Finally the switch with the new 9k1 resistors seems to work.

The only problem i have is the orientation of the switch. When i turn it to the left sounds the right speaker, in center, both, and turned to the right sounds the left speaker. I think it can be changed moving the stop.

I tested a bass drum from a drum machine (Roland CR8000) and whe the sound comes from left speaker the bass drum sounds with a bit less punch, less low end . At center there is a  slight increase in volume. And when the sound comes from the right speaker the volume is just a bit lower but noticeable, but with low end.

Maybe these differences in sound quality between left and right speaker come from the summing amplifier, that still has that imbalance in the signal between the left and right channels. ( i have not made any changes in it yet).

Thank you Harpo.

JAY X

can we see the schematic too  ???

kambo said:

can we see the schematic too  ???

Click to expand...

The assign switch is from the pdf by New York Dave : Balanced mixing network. Look carefully in this thread, my first post.

JAY X

most NYDave schematic links are broken... although never seen this schematic before... believe me i have been searching/reading a lot for summing stuff..
and its strange that, circuits link is at gearsl*z, not at prodigy
anyway, thanks a million
kam

JAY X said:

Finally the switch with the new 9k1 resistors seems to work.

The only problem i have is the orientation of the switch. When i turn it to the left sounds the right speaker, in center, both, and turned to the right sounds the left speaker. I think it can be changed moving the stop.

I tested a bass drum from a drum machine (Roland CR8000) and whe the sound comes from left speaker the bass drum sounds with a bit less punch, less low end . At center there is a  slight increase in volume. And when the sound comes from the right speaker the volume is just a bit lower but noticeable, but with low end.

Maybe these differences in sound quality between left and right speaker come from the summing amplifier, that still has that imbalance in the signal between the left and right channels. ( i have not made any changes in it yet).

Click to expand...

Hi Jay,

Easiest fix for a L/R swap is probably done by swapping the bus inputs of your L or R summing amps (or their outputs, maybe at the XLR or TRS plugs). Eigther way its only 4 cable ends to exchange/resolder.
The assign switch end-stop washers are unlikely the cause. You want exactly 3 positions for L/C/R. Just in case, pull the washers out, turn your switches full ccw and put the end-stop washers back in to pos.3 (the 2nd hole).
Sound and volume imbalance between L and R can easily be checked with a mono source by swapping your summing box outputs. If misbehaviour follows the swap, its the summing box, else its your monitors, monitor amp or your room/listening position.
-Harpo