[Winetree]

I want to make a Microphone Switch Box, say 5 to 1,
so I can audition a number of different Balanced Mics through the same preamp.
I figured this would cutout any variables in the chain.
Could it be as simple as a switch, switching the different Mic inputs.

Questions; Could switching be done without having to turn down the pre or control room volumes.
                 What about the  Phantom powering?
                 Would this cause any harm to the preamp input?
OR;           What would be the best way to design the switcher box to include the above issues?

[pucho812]

you would be better off buying a mic mate by manley labs. In the long run would be easier. But if you wish to diy an option, For starters I could see phantom being a huge problem as you would get pops, much like patching in at a patch bay, when switching from mic to mic unless you did something like have phantom built into the switch box and having it so each mic gets phantom all the time.  From there you will need phantom blocking caps in the event your using a transformerless mic pre.  from there I could envision a bunch of DPST relays that a rotary switch or other type of switching controls which relay gets the required voltage to operate it.  But that is just off the top of my head and I am sure there is a lot I am not thinking of.

[MagnetoSound]

48V supply (could be applied externally), 6k8 phantom resistors, 100uF blocking caps with cathode grounding resistors (6k8 again or higher), 2-pole rotary switch. Done.

(Make sure phantom is turned OFF at the preamp.)

[mikeyB]

Good pointer, Pucho, to the Mic Maid, not seen that before, liked it and then saw the price - gulp!!
Could be an Igor project - reusing his monitor type switcher - stereo pair/mid side switches would be most lovely!

[Winetree]

Dan; I like to wire one up.
Would a diagram be possible?

[sodderboy]

Even with the P48 powered to all mics and blocking caps you will still get pops due to the high gain involved, so will have to cut volume during switching.  Even with a make before break switch.  Plus you will be changing gain a bit for different mice.
And mic placement is everything so you will have to deal with that.  Does a mic really sound better, or is it simply in the correct place compared to another?
Mike

[CJ]

you could use a small mixer if you have one laying around,

[pucho812]

you could use a small mixer if you have one laying around,

worked for motown when they were in detroit.

[JohnRoberts]

This is complicated to make it completely apples to apples, and not have switch perturbations.

Better perhaps is to have a number of identical preamps and switch the outputs.

It is far easier to make identical preamps than identical mics.

For a fair comparison you want to normalize volume for sensitivity, and make sure the mic is physically in the same location wrt any nearby room boundaries.

I recall using an automatic mixer at trade shows to demo different microphones using headphones. This way the noise of all the not active mic channels was ducked so you could hear mostly just the mic you were speaking into.

For very critical listening I don't know that you need so much drama.. Mics vary widely in frequency response and pattern so they should be pretty different sounding already without so much work.

JR

[MagnetoSound]

A small mixer, gains at parity, is probably the best solution I agree.

If you want to knock this up however, here is how I would do it. The tie-down resistors should minimise switch pops by grounding DC at each switch position. A transformer balanced preamp input with no phantom applied should work fine with this, but I agree that pulling the monitors down might be prudent, at least until you verify that it is safe to leave them up.



(XLR pins to the left, switch contacts on the right, duplicate per channel.)

[Winetree]

Thanks, I know a lot of facts come into play.
All this can be done at the patch bay using a single mic pre with a mute and phantom button.
Just thought a box might be easier, but easier is alway easy. Thanks for the responses.

[Winetree]

I asked this awhile back and it seemed it couldn't be done.
Well, Radial Engineering came out with a passive 4 channel,
phantom power, trim control, mic switcher. $400.00

http://www.youtube.com/watch?v=DcjA-yym3rE

Why couldn't some of our brilliant DIY minds come up with something?

[MagnetoSound]

That box has LEDs, momentary pushbutton switching (presumably CMOS), gain trimmers and ... power. Doesn't look very passive to me.

And ... $400? Really? 

[Majestic12]

Why couldn't some of our brilliant DIY minds come up with something?

Well, I made something similar half a year ago....

[andre tchmil]

Why couldn't some of our brilliant DIY minds come up with something?

Well, I made something similar half a year ago....

Brilliant Idea , not new new , but the mic / preamp input is .

[Rochey]

now you need four or five of these stacked, so once you've decided what to do with mic#1, you can move on to mic #2

[joaquins]

now you need four or five of these stacked, so once you've decided what to do with mic#1, you can move on to mic #2

And a couple of robotic stand to move the mic from the control... (is something pending for me, really nice for snare or guitar cab)

JS

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