Bypass box for balanced signal

[telepathy]

hey guys. I'm the pain the ass that came up with this thing, and Keene is my guru when it comes to homemade electronics, so the problem fell on his shoulders.

I'm a FOH guy by trade. I see a lot of bands who want to process their vocals take a varied number of unsatisfactory approaches to doing so. you know, XLR-->1/4" cable, straight into a distortion pedal or something, then into a DI box to get to FOH. sounds like hell and extraordinarily compromises my ability to get good clean gain on the console thanks to the loading-down of the unhappy mic signal. I recently joined a band where the singer uses distorted vox plenty on the record, and expressed a desire to be able to do so live without compromising his "clean" vocal sound.

I came up with some rules for myself:

a dynamic mic input needs to be fed to a balanced effects loop that is triggered stompbox-fashion by the singer. in that effects loop will be a Blue Tube, or one of those ART "tube" pre's: something agreeably shitty sounding to be used as a distortion device. the signal then needs to be fed back into the loop and out the XLR out of the switchbox. there would be no line level conversions, no DI box involved, and no two-different-ouputs to FOH. if we were touring with our own soundguy, I'd simply buy this:

http://www.radialeng.com/re-hotshot-dm1.htm

and have two channels up on the board, clean & dirty, setting whatever gain and monitor levels were required. but this band is a six-piece with four vocals and three DI's and a big mess already, so we're in no position to ask the soundguy in Peoria IL to handle two vocal channels FOR THE SAME SINGER while he's trying to deal with the cello and the moog and the sampler and .....

anyway, I did a really poor block diagram assuming I'd have to use a 4PDT switch (5PDT doesn't exist, right?), to switch the hot and cold legs of the input to the loop (most likely using 1M pulldown resistors to eliminate popping when the loop is engaged, I guessed), then routing the signal to the mic pre, where it would be gained up using the "tube blend" control, with the main out as a master volume, then back into the loop and XLR out.

problems I encountered when thinking about this were: 1) most cheap mic pre's have unbalanced outs. I have to get one with balanced outs. 2) I want the clean signal to be CLEAN, as in, unloaded and able to respond to the console's mic pre in such a way as to provide the usual amount of headroom that mic would be capable of (it's a Beta 58, by the way) to have plenty of signal for the stage monitors. it's easy with a six-piece band for the vocals to get lost in a poor stage mix, under all those guitar amps, and with all those DI'd signals coming back in the monitors. 3) my amateur electronics knowledge led me to wonder if a 1:1 transformer would be necessary to drive the loop. apparently not? 4) the issue of whether or not the two signals would react extraordinarily differently to FOH console gain, since the effected signal would've passed through an extra gain stage.

Ned's diagram is killer. it's nice to have the line-level-out option even if we choose not to exercise it in most circumstances. the pad switch on there totally takes care of problem #4, above. I imagine we'll use a 3PDT to be able to allow for an LED. that shouldn't be a problem, right? have to include 9V in there somewhere, most likely through a wall-wart since the effects-loop mic pre will have to be powered, too, so the whole thing will probably end up on pedalbord or something.

by the way, why in the hell doesn't something like this already exist? there are so many guitarist-specific signal switchers out there....

thanks for the help, everyone!

[brianroth]

Greetings, telepathy.

Tis late, and I'm "shootiing from the hip" here...

If we ignore phantom powering isssues...

With a typical dynamic mic, you CAN "mult" the mic into more than one preamp
load.

For line level balancing transformers, look at:

http://www.edcorusa.com/products/xmatchers.html]

Bri

[moosapotamus]

The singer in my band has been asking me for (almost) exactly the same thing - an effect loop box for his vocal mic. Except, instead of just one effect/preamp, he wants to be able to use several different effects... distortion, phaser, ring modulator, etc... So, I started drawing up something that would have balanced input/output and an unbalanced effect loop for a string of stompboxes. I also threw in a wet/dry blend control for good measure. So, here's my initial take on this...

http://moosapotamus.net/IDEAS/MicBoxSCH.gif

It's not quite complete and I haven't tried building a prototype, yet. None of the switching is shown. But, the idea would be that he can have his own little pedalboard, just like a guitar player. Setting levels so as not to give the FOH guy fits would be his responsibility, just as it's the guitar player's responsibility to keep all his pedals under control.

~ Charlie

P.S. Banzai appears to sell a 4PDT stompswitch...
http://www.banzaieffects.com/Japan-4PDT ... 16235.html