Rebote 2.5 for vox

[zpyder]

I brought this up previously but want some fresh opinions.........:

I'm building a Rebote 2.5 for use on vocals... think reggae gae gae gae gae gae  THIS IS A TAKEOVER VER VER VER VER

Anyways, it's preferable if the unit is a simple as possible to use live and at practice.  IE, I want the unit to be in-line, before the PA, not in an fx loop.  It seems the best/coolest solution would be to use XLR input and output jacks.

What do I need to know to install XLR's into a rebote 2.5 stompbox?  Does this require a transformer?

thanks,
zpyder

[zpyder]

bump

[markm]

I think you may run into some impedance issues doing this but, I'm not sure.

[John Lyons]

See if you can dig up a low to high impedance converter (they work backwards as well) Mics are low impedance and guitar pedals are high imp. Radio shack used to sell them. Looks like a big metal XLR to 1/4" plug about 4 inches long and an inch in diameter. You will need another for the output unless you can run the output of the pedal in to a high impedance input on your PA.

John

[cakeworks]

See if you can dig up a low to high impedance converter (they work backwards as well) Mics are low impedance and guitar pedals are high imp. Radio shack used to sell them. Looks like a big metal XLR to 1/4" plug about 4 inches long and an inch in diameter. You will need another for the output unless you can run the output of the pedal in to a high impedance input on your PA.

John

If I was to run a series of effects I wiould only need one low to high converter at the beginning and at the end of the series right?

[zpyder]

basicaudio-
Ok... simple enough.  BUT    How can I make my own?  What's inside of a low-high impedance converter?

cakeworks-
that sounds perfectly reasonable to me.  As basicaudo said, mic inputs are low impedance while stompboxes are high.  From your mic you'll need one to raise it to high impedance, then you should be able to put any series of high impedance input devices in between, and then on the way to the PA, you'll need to convert back to low impedance (unless the PA will take a high impedance input - which it almost assuradly will, just at 1/4", not XLR)

zpyder

[Pushtone]

An easy way to do it would be with two PASSIVE direct boxes.
And when I say PASSIVE I mean a DI with a transformer. ie not an active DI.

The reason for passive is you will be using one of the DI backwards.

Plug the XLR cable from the Mic into the XLR "output" of the first DI.
Plug the 1/4" "input" of the first DI into your efx pedal input.
Plug the output of the pedal into the input of the second DI.
Plug the XLR output of the second DI into you mixing console mic input.

I use my passive DI backwards for re-amping sometimes.

If you wanted to do this live I think you could make use of one of these switcher products
from Radial Engineering along with two mixer channels on you PA console.

One channel for your straight vocal the other for the Mic with effect pedal.
I really don't see a way to do it live without using two mixer channels.

http://www.radialeng.com/re-hotshot-abo.htm latching footswitch
http://www.radialeng.com/re-hotshot-dm1.htm momentary footswitch

The mic preamp on the console should be able to make up any loss of gain.
Or you could put a booster in before/after the delay pedal.

[zpyder]

I really don't see a way to do it live without using two mixer channels.

Why couldn't I just use two DI boxes live??  Or better (cheaper) yet, why couldn't I just use two impedance converters live as basicaudio suggested?

What's inside an impedance inverter?

This all seems overly complicated - I'm just trying to put delay on vocals.... hmmmmmmm

thanks tho!
cheers,
zpyder

[lumpymusic]

Assuming the mic is dynamic (doesn't require phantom power)
Try it direct, no transformer or DI. Connect the mic output XLR pin 1
to ground on your stomp box. Connect the mic output XLR pin 2 to
TIP on your stomp.

It might(?) drive it just fine, depending on the gain of your box
and how quiet the entire circuit is.

Other things to consider -

On the mic side of the adaptor(s) ground pin 3 to ground (pin 1).

If your stomp has a pulldown resistor at the input (2.2M or so),
eliminate that or change it to a smaller resistance, maybe 50k-100k
so that the ratio of source to input is closer to 1:10.

Consider adding a simple JFET or single transistor buffer/booster
to the front of your stomp to make up for the low level signal
coming from the mic.

Overall, probably the simplest and easily reversible would SEEM to be an
XLR Female low imp to 1/4" male hi imp matching transformer
between the mic and the stomp. BUT those transformer assemblies
tend to be long, heavy monsters. They put a lot of stress on the
connections and give you several inches of plug body sticking out
of the input side of your stomp. The guts of the adaptor is a simple
transformer. The schematic of the transformer is typically printed
on the outside of the barrel. You could dismantle the heavy metal
assembly and use the transformer.

Or you could find a similar transformer without all the metal.
They are typically expensive (Jensen) if they have a good audio
bandwidth. If you don't care so much about bandwidth (maybe
100 ohms to 10k ohms) you could use a cheaper transformer.

Lumpy
--
Can you do that FM disc jockey voice?
Yes, but it doesn't translate well in ascii.
www.lumpyvoice.net

[Pushtone]

I really don't see a way to do it live without using two mixer channels.

Why couldn't I just use two DI boxes live?? 

One mixer channel might work depending on the delay settings.
From mixing thousand of shows my gut feeling is that the delay
mic sound will need different EQ, and monitor send levels,
hence two channels on the PA console. I was also thinking this method would
work for ANY effect pedal, even crazy stuff like vocal through a Scambler.

why couldn't I just use two impedance converters live as basicaudio suggested?

A DI is an impedance converter.
When I said easy I meant without building something. DIs are ubiquitous.

I'm just trying to put delay on vocals....

No your not. Your trying to use a high impedance guitar
effect with a low impedance microphone.
Two peices of equipment not designed to work together.

If all you wanted was delay on vocals then the proper way would
be to connect a digital delay to an aux send from your PA console
and instruct your sound mixer to put some delay on your mic and
ride the delay return fader at the end of a vocal phrase phrase phrase

Gee now that I think about it again why not just connect the delay
pedal to the aux send and return of your mixer with high impedance
guitar cables. That will work fer sure.

But, if you try to get the house sound mixer in a club to do that
you might get some funny looks before they say "but I have a
perfectly good SPX990 right here already connected to aux 1".

I took it that you wanted to control the delay yourself from the
stage which means you will still be feeding a console mic input through a mic snake.
For that you will need the two impedance converters and the sound might be degraded
(in a cool effect way) to the point where you would want your straight vocal on a separate
channel. That is if you enjoy hearing yourself in the monitors and not fighting with the monitor mixer.

[zpyder]

thanks for the replies guys... I think I'm getting somewhere

On the mic side of the adaptor(s) ground pin 3 to ground (pin 1).

Okay, that was some info I need... Without knowing, I am guessing that the 3 pins in an XLR are: pin 1 Ground, pin 2 Signal, and pin 3 Balanced Ground.  The balanced ground being a stable reference and therefore an advantage over an unbalanced 1/4", good for utilizing a low-level mic signal (am I close?)
So connecting pins 1 and 3 both to ground sounds right - my concern is:
What about with the effect bypassed?  This effect would be used intermittently and I would like to retain the balanced ground when the delay is bypassed.  Will connecting 3&1 present a problem here?

After thinking about it, I came up with this... utilizes a 3PDT and the Milenium bypass circuit:

The left 2 poles are nothing more than a milenium bypass switch setup, the right pole is an on/off between the balanced grounds and effect ground.  I wonder if this is even necessary?

If your stomp has a pulldown resistor at the input (2.2M or so),
eliminate that or change it to a smaller resistance, maybe 50k-100k
so that the ratio of source to input is closer to 1:10

Consider adding a simple JFET or single transistor buffer/booster

Both seem like good ideas... something I'll have to play with.

A DI is an impedance converter.

Thankyou for spelling it out in plain noobie language   I guess I knew that, but, well couldn't put it together...

No your not. Your trying to use a high impedance guitar
effect with a low impedance microphone.
Two peices of equipment not designed to work together.

I took it that you wanted to control the delay yourself from the
stage which means you will still be feeding a console mic input through a mic snake.

Bingo... Your're right... That is exactly what I want to surmount... That and I have no idea the pinout of an XLR, but I think I'm getting it.  Considering that this effect isn't even intended to be "musical" (yet!) I'm more concerned with maintaining normal vocal signal when bypassed than when engaged.  It's only going to be used for BS blabla between songs and the such... (Having said that I'm sure it will find it's way into the tunes somehow...) So I want my bass player to be able to get normal, clean vocal signals all the time, and then kick in the delay between songs for some "Tip your bartender der der der" etc...


My plan as of now:
Try the 3PDT/Milenium layout I posted above
Play with elimating/reducing my pulldown
Play with a clean JFET boost before the delay

Failing this, I suppose I'll be looking at transformers

Right? Wrong? Anything else?

THANKS!!!!!!!!!!!
zpyder

[Pushtone]

Will connecting 3&1 present a problem here?

Connecting pins 1 and 3 will unbalance the signal.
This is a common thing to do when you want to terminate a balanced line
from an XLR source into something like an RCA connector.

Pin1=ground
Pin2=signal (sometimes called pin2 hot)
Pin3=inversion of signal (sometimes called pin3 cold)

Pins 2 and 3 carry the same signal but one is 180 degrees out of phase. The concept is this,
If induction occurs in the cable from magnetic fields or RF it will be cancelled out when the two signals are combined again.
When I say combined I mean through the help of an inverting dual amplifier like a TL072 where one half is used for the positive phase (pin2) and the other half for the negative phase(pin3).

I think the RANE website has a tech note that fully explains this.

It bears to mention that older PA gear like mixers, cross-overs, graphic EQs sometimes switched the pins as the manufacturer desired. I spend many a day getting ready for a tour in the shop converting pin3 hot gear to pin2 hot. A lot of UK manufacturers like BSS and KT used the pin3 hot non-standard. US manufactures like Ashly used pin2 as hot or positive.

It was only a few years ago the AES.org set the XLR pin standard they call AC3 or something like that. It declares pin2 to be hot or the non-inverted signal to help get rid of phase problems in balanced systems. Connecting one piece of gear that is pin2 hot to another piece that is pin3 hot will throw your signal out of phase.

I remember one time when I walked into sound check and the house tech was trying to fix something wrong with the subwoofers. The harder he pushed them the less bass there was. Turned out that one of two subwoofer power amps has failed and the replacement amp was  pin3 hot, the other amp pin2 hot. Result was phase cancellation that sucked the bass right out of the air. One side of subs was pushing out while the other side was pushing in. Luckily I found it before he burned out the voice coils.

All this about pins 2 and 3. Don't get me started on chassis ground vs signal ground. But on the other hand...
If it weren't for these issues caused by manufacturers I would have a lot less (paying) work in the PA rental biz.

Balanced ground? Never heard that before. Please don't take offence but it sounds like marketing gook that Monster cable would use.

I've been thinking on this all day now and I think you should build an effects loop box that would allow you to connect any effect pedal to a mic. It would have an XLR input and output with a 1/4" effect loop. I wish I knew more about electronics to help. I will ask the head engineer at work. I know it will need transformers but will it require a buffer? Probably if it is to be used with any effect.

I'm most familiar with Jensen transformer so I'll use their website but you won't want to pay this kinda price.
For the mic input maybe the JT-115K-EPC with is 150ohm-15k impedance ratio.
http://www.jensen-transformers.com/mic_in.html

And for the effect out to balanced mic maybe the
JT-1061-1m on this page http://www.jensen-transformers.com/ln_out.html

By any chance are you doing dub music? Reggae dub that is.

[zpyder]

Pins 2 and 3 carry the same signal but one is 180 degrees out of phase. The concept is this,
If induction occurs in the cable from magnetic fields or RF it will be cancelled out when the two signals are combined again.

Brilliant!  I love solutions like this!  Didn't even know I was using it all this time

Balanced ground? Never heard that before. Please don't take offence but it sounds like marketing gook that Monster cable would use.

Well I guess I just came up with that term.  The concept I was going for was the same - transmitting that low-power signal, but clearly I was taking a stab in the dark.  The given method is clearly superior.

It bears to mention that older PA gear like mixers, cross-overs, graphic EQs sometimes switched the pins as the manufacturer desired.

This would explain some odd experiences I've had in the past and will be something I keep in mind while gigging in the future.  thanks!

Connecting pins 1 and 3 will unbalance the signal.

Okay... I believe that the switch setup I posted before would leave the signal balanced when bypassed, while unbalancing when going into the effect.  Unless I'm missing something, this would seem like the right thing to do:

Simply: The inverted pins are always connected, and when the effect is engaged, they are dumped to ground.  All this while true bypassing the effect having an LED indicator.  I wonder if this is going to require a pull-down resistor and/or cap to prevent switch popping......?

I've been thinking on this all day now and I think you should build an effects loop box that would allow you to connect any effect pedal to a mic.

I've been getting toward that conclusion as well.  I guess at this point I am looking at all alternatives.  Would be interested to see what your engineer says...

Jensen transformer

Hot damn those are expensive!

By any chance are you doing dub music? Reggae dub that is.

No, fraid not.  We bill ourselves as rock, though we do play some reggaeesque (whoa) riffs.  We like to go all over the place.  You can listen to some demo recordings on our site at http://www.mattrabe.com/ultraterrestrial/.  We're recording right now   However, this vox delay is for the bassist, who is indeed a reggae fan, and I'm positive that's where the influence comes from...

thanks a bunch!
zpyder