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[J.J. Blair]

I have a very early 3124 here.  (3124micP serial #0019 to be exact.)

I want instal a phase switch, but I am wondering of the best method is to sever the XLR ins from the mother board and run leads to a switch on the face plate (plan A), or if there's some better way, such as another contact point on the motherboard that can be jumpered, etc.

Anybody with a schematic for these guys have an idea?  Or should I just go with plan A?  I didn't realize that they were sort of hard mounted to the board, which made me wonder of there were a better method.  Thanks.

[John Monforte]

Thinking aloud here- Running mic level signal from back to front and then front to back passing near all those line level signals and power supply... well, that's not a trivial exercise. It probably will not add to the resale value of the unit either.

Old consoles rarely had such switches, and that was back in the day before pin 2 was deemed hot! Neanderthal engineers like me carried phase flippers, hi pass filters, attenuators, combiners, splitters, isolators, ground lifters, and direct boxes that we built ourselves. I still have mine, even though I can hardly remember when I last used one of them.

I would be inclined to employ an appropriately wired Switchcraft S3FM and slam it on any input that needed it. It works on anybody's preamps.

[zmix]

...system glitch...

[zmix]

JJ,

I would recommend that you install a simple DPDT switch between the output transformer and the XLR connector.

This method places the switch at the point of the highest possible signal level.

..and as a bonus you can also invert the signal polarity when using the preamp as a DI.

-CZ

DPDT SWITCH:

1 0     0 2

3 0     0 4

5 0     0 6


Connect transformer secondary to pins 1 and 2

Connect XLR (2&3) to pins 3 and 4

Wire pin 5 to pin 2

Wire pin 6 to pin 1

[J.J. Blair]

John, I have phase flipping connectors and even phase reversing points in my patchbay.  I'm concerned about being able to flip the polarity on my toms and hear the effect against my other mics, etc.  It's speed I need more than resale, but good point to consider.

Chuck, thanks for that.  I'll give that a whirl.

[zmix]

JJ, feel free to give a call if you have any questions.
-CZ

[ssltech]

I'd consider (if you have a 1RU blank or ventilation panel to spare) wiring several such-wired Double-Pole changeover switches (labeled "phase-reverse") onto a panel above, below or otherwise near to the APIs. Then wire a length of balanced-cable-to-XLRs, male and female. This way, you can have them be always in-line with the outputs of the APIs, with no significant added loss of sonic integrity. The front panel thus stays un-drilled ad unmolested, and if you realise that you could use a few for OTHER, similarly "polarity-flip-deficient" pieces of gear, you also can have them available to you.

-Or you can drill holes in the front panel, but I'm always less nervous about drilling in blanks for that sort of stuff.

I do a lot of things that way: the link switch between a pair of LA-2A's, the link switch, preset and battery-reverse switch for an SA-1176 (Urei Stereo adaptor) and other such things that would otherwise necessitate a trip round the back of the rack... just wire them to switches on a spare rack blank, and party on.

Keith

[J.J. Blair]

Keith, that is an excellent suggestion.  However, rack space is at a premium in my room.  I mean honestly, everybody I know wishes that APIs has phase switches.  I can't see four well done switches harming the value that much.  These aren't 1073s.  

[Dave Hecht]

Ran into the same problem with an API Legacy. Client wanted phase reverses on the pres. Middle of a session, couldn't get in to work on the console. Ended up chopping up 1/2 dozen patch cables, installed dpdt switches ( I think they were isostats or shadow) for phase reveerse. Tie wrapped the cables to switch body, covered in shrink. Worked great.

Dave Hecht

[Barry Hufker]

J.J.,

Why not ask API to do it?  I bought mine years and years ago.  Even then they were doing custom phase reverse mods.  Mine has their mod.

Barry

[J.J. Blair]

Barry, isn't it always more gratifying to do it yourself?  It will cost me an hour or two and $30 for parts, as opposed to how much time and money for API to do it?

[Barry Hufker]

Maybe.  But how much time have you spent on this forum already asking about it?  And, what if you don't do it at some optimum section in the signal path?  And what about drilling the extra holes?  And... I can't think of anything else.

It may be fine for you.  I have learned in life that I am no good at such things.  My talent appears to be paying other people to do everything for me (and no, I'm not rich, just inept).

Best of luck.

Barry

[J.J. Blair]

Thanks to Chuck for helping me sort out where to tap the transformer for this.  Below, you can see where I spliced into the transformer lines, heading to the switches, which I installed in the faceplate, and then ran lines back into the circuit board where the transformer had been connected.  And you can see the front panel with the switches installed.

BTW, I did the drilling myself, Barry.  Took all of about 3 minutes.

[Barry Hufker]

You're the Man, man!

Barry

[zmix]

JJ,

Happy to help. The switches look nice and the wires all have shrink tubing. Very nice.

It looks like you have 6 wires running to the switches... (there should only be 4).

-CZ