Help picking channel out points - schematic

[slowmotion]

Hi guys

I've got a funny old desk that I want add in a couple of channel outs. I think I know where to take them from - BUT I want the echo to still work for each out though (which makes things trickier maybe).

Here's the whole schematic:

Here's what I'm thinking:

Question is; can I sneak a couple of extra wires for each channel from the echo returns (on the schematic, just a bit to the right after the dotted line) and wire them to the channel out points too? I think maybe I could. Maybe any channels that I do this on might get a double dose of echo returned?

Any input appreciated!

 

[dgatwood]

It's a mono input, so it makes no sense to tap it after the pan pot. You definitely want to tap it earlier in the circuit than that. The absolute latest you should even consider tapping it is right after the capacitor on the output of IC48.

That said, assuming you're just trying to tap the preamp output, I'd probably tap it way back where it has that arrow that says "To Alternate Line Input Stage" (and again, probably after the capacitor). The output of the mic stage at that point is likely to be at least line level, if not hotter. Put yourself a simple tap at that point out to a jack. If the output gain there isn't hot enough, move the tap to after the cap on the output of IC48, but I doubt that will be necessary.

I'm not sure it's worth the effort to compute the gain at various stages in there to come up with the one right answer—it's too much easier to just tap after the mic preamp stage and see if the output is hot enough, and if not, tap it after the secondary amp stage.

Either way, I'd be sure to put a small decoupling capacitor inline between whatever point you tap and the output jack just to be safe. If this is an old board, there are probably lots of little DC offsets running around.

Just one more note. I assume you just mean that you don't want to break the echo send/receive. If you mean that you want echo on each channel out, that would be a major redesign. The echo I/O happens in a completely separate path there.

 

[dgatwood]

Question is; can I sneak a couple of extra wires for each channel from the echo returns (on the schematic, just a bit to the right after the dotted line) and wire them to the channel out points too? I think maybe I could. Maybe any channels that I do this on might get a double dose of echo returned?

You would definitely get double echo returned. I'm not sure why you'd do that anyway. If you have outboard echo, you'd probably want a separate echo unit per channel, not the echo from everything mixed with each channel. If you want to record the echo, instead of putting a tap at the points I mentioned, put a channel insert jack instead.

To do this, you need a switching jack. Wire up the tip to the output of the preamp stage, the ring to the input of the next stage, and hook up the switched contact for the tip up to the ring or vice versa. If nothing is plugged in, the tip effectively shorts to the ring, and it behaves just like it does now. If you plug something in halfway, it behaves like a tap. If you plug something in all the way, tip is a send and ring is a receive.

Then hook the send to the input of your reverb unit, hook its output to your audio interface, and either hook your audio interface's output to the return or split the output of the reverb unit two ways and hook one directly to the return.