Adding balanced XLR output to a pedal

[Muadzin]

Isn't the unbalanced out usually taken directly from the input tip?

[Jopn]

Good question, since the input would then be connected to both the circuit and a passive pass-thru I think you'd be likely to get some "tone suck" on the pass through.  I'll be adding the AMZ super buffer in line with the pass through.  I haven't stared at this layout enough to be able to tell if there's an input buffer section after which you could potentially steal your unbalanced pass-through instead.

On Sat, Mar 8, 2014 at 8:22 PM, Muadzin [via Guitar FX Layouts] <[hidden email]> wrote:

Isn't the unbalanced out usually taken directly from the input tip?

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[Lazy Swamis]

I think you can take your unbalanced out from pin 3 of the xlr. One of the earlier schemes had that.  You just get one side of the signal then, without the other inverted half as I understand it. You need both sides to be considered balanced.
Not an expert (or even knowledgeable) by the wildest stretches of imagination though.

[Jopn]

Lol, yep, I was definitely overthinking it!  XLR pin 3 should be exactly what you're looking for, thanks LS!

[jaredcohen]

If anyone happens to know... if I wanted to put a switchable cab sim inside a DIY box (kind of like a less impressive Palmer PDI09) would I wire it as Input -> Cab Sim -> Active Direct Box -> XLR Out?

Follow up question: in terms of switching the cab sim, would it make more sense to
 1. run always-on power to the DI board and have a switch to turn power to the cab sim on or off?, or
 2. to actually switch the cab sim board out, more like the switchable pre-boost wiring in the Offboard section?

Thank you to all of you who are much smarter than I am.

[Jopn]

jaredcohen wrote

If anyone happens to know... if I wanted to put a switchable cab sim inside a DIY box (kind of like a less impressive Palmer PDI09) would I wire it as Input -> Cab Sim -> Active Direct Box -> XLR Out?

Yes, that's the order that I'd do.

jaredcohen wrote

Follow up question: in terms of switching the cab sim, would it make more sense to
 1. run always-on power to the DI board and have a switch to turn power to the cab sim on or off?, or
 2. to actually switch the cab sim board out, more like the switchable pre-boost wiring in the Offboard section?

#2 is what you'll want to do.  If you kill the power to the cab sim but don't switch the signal route, your signal will die the moment it hits a dead opamp.  Leave the power on, and switch around it like that pre-boost wiring you're looking at.

[jaredcohen]

Awesome, thanks Jopn!

[alex.s]

Shouldn't the unbalanced output be taken from the Balanced+ out (XLR pin 2) rather than 3?

[vmaxvmax]

Hi, I am just about to build this - Thanks! But, the diagram asks for 15 cuts. I can only find 14... Is it my eyes?

Best wishes and thanks for the scheme!

[Jopn]

vmaxvmax wrote

Hi, I am just about to build this - Thanks! But, the diagram asks for 15 cuts. I can only find 14... Is it my eyes?

On the last one I only see 14 as well.  JohnK had cut down the size, and probably forgot to update the cut count.

[Muadzin]

This could be very useful. I'm thinking a dirt circuit, a noise gate into this balanced out so I can do distorted vocals.

[vmaxvmax]

Yep, I figured that was probably the answer. I was just too lazy to check the circuit...

[cylens]

this thread is kinda old, but just a quick message since I just built it: i wouldn't recommend using johnk's last layout, since there are a couple of mistakes: the 1uF cap is connected to the IC while it shouldn't and there's a cut missing between the 100R and 6k8 resistors (they're parallel, there) and the second 6k8 resistors should connect to the bottom of the first one, not the top).

any recommandation how to make a pre/post parallel output? adding a buffer/splitter?

[Sensei Tim]

necro bump and question:

what happens if you plug in an XLR cable that happens to have 48V phantom power enabled?

are there some some diodes that would need to be added to protect the circuit in case this happens?

[Travis]

Hey guys this is an old post but I’d like to add that if you are designing a project where unbalancing/balancing are required the easiest option is usually one of these parts from THAT Corp.

Here’s a link to some balanced line drivers
http://www.thatcorp.com/1600-series_Balanced_Line_Driver_ICs.shtml

I’ve seen NE553x used a lot as well because it can drive a 600 ohm load but if you use a design like this make sure to use the right IC or one with enough drive capability