XLR input/output for using a microphone with zeropoint micro II pcb

[Lubdar]

Hi everyone,
   I wasn't sure if I should ask this here or in the Tech help section, so I apologize if this is in the wrong place. While I am mentioning the ZP micro II, I was just wondering in general about building an effect pedal for use with microphones.
I'm looking into how feasible it is to build a quasi-vocal delay pedal.
In my naivete I would think that I just connect the PCB in and PCB out to XLR male and female connections, but then again, I don't know much in this area.

I'm wondering what/(if there) is a way to go about using XLR male and female jacks for connecting a microphone to the zeropoint micro II pcb, are there any references/resources that someone could point me toward?

Best,
   Lubdar

[Muadzin]

The problem is that you're trying to put a balanced signal into an effect device which takes only unbalanced in- and outputs and then have to find a way to make it balanced again. The solution that I see most people using is they take an unbalanced microphone cable with a mono output jack, insert it into the effect pedal, and then patch that pedal with another mono cable into a DI box which converts the signal into balanced.


http://toffer.com/wp/wp-content/uploads/2011/03/3pin_XLR.png

Easiest solution would be to install a female XLR socket for the input and a normal jack socket for the output. Ground would be connected to pin 1 of the XLR socket and the input to pin 2. Pin 3 is left unconnected. Since we're producing an unbalanced circuit that has to be converted into balanced by a DI box a normal mono jack connection for the output will suffice, as any decent DI box will have such an input. And if the mixing desk is close by a standard mono cable of up to 6 meters will do fine anyway. Balanced signal is basically only required to drive signal through long cables.

If you want you can add an additional circuit that will convert your signal into balanced. I think I saw a vero in the layout sub forum of the Tagboardeffects forum. If you're going to do that then you no longer need to patch it in into a DI box first, in which case you should then use a male XLR socket for the output instead.

[midwayfair]

$10 on Amazon:



http://www.amazon.com/Female-Male-Line-Matching-Transformer/dp/B0002BF1KG

[Lubdar]

Ahh thank you both, I'll look into it further and let you all know how it goes.

[oldhousescott]

Ted Weber sells a little Balun transformer (balanced/unbalanced) for $4 that can be board mounted. Their hookup diagram shows its use as a line out, but you could use it for both input and output on your effect. Low-end freq response isn't that great, but for vocals it should be fine.

[Lubdar]

Hmmn that's interesting as well.  I recently purchased the THcustom balanced line driver in the BST section, which i suppose I can use at the PCB output to run XLR out?

[oldhousescott]

Yes, that will work fine. You can also do a balanced line input with a single or dual opamp and a couple of resistors on perfboard if you want to keep it all in chips.

From the Douglas Self site:

[alanp]

What exactly is going on with the Fig 12 schematic?

[Lubdar]

If anything I'd like to try and build it all straight into the enclosure, I'm looking at the amazon option, but my curiosity would lead me to prying it open and trying to figure out what it's doing inside...

[midwayfair]

If anything I'd like to try and build it all straight into the enclosure, I'm looking at the amazon option, but my curiosity would lead me to prying it open and trying to figure out what it's doing inside...

It's a transformer.

[Lubdar]

Heh fair enough

[oldhousescott]

From the Self site:

"The "Superbal" configuration (figure 12) gives much better input symmetry than the standard differential amplifier. The differential input impedance is exactly 10k via both hot and cold inputs. Common mode input impedance is 20k for both inputs."

I figured if one were to use a dual opamp, they might as well use the other amp for better performance.

[stecykmi]

it looks funny, but it's just negative feedback.