Try to plug dynamic mic into guitar pedal. Need help on the converter

[NBguitarist]

I know I need something like audio technica cp8201, Which shoulb be made of a simple transformer.
Can someone please suggest how to build one myself.

Many thanks.

[MrStab]

i've been looking into something along these lines for my singer. Check out this thread: http://www.diystompboxes.com/smfforum/index.php?topic=95855

if you scroll down, you'll find this schematic, courtesy CynicalMan (might wanna read the rest of the thread for further details):



no transformer, though.

[NBguitarist]

Isn't op amps need battery to power up?
I don't think the cp8201 need to take the battery.

Btw. Thanks for useful information. Is is schematic verified yet?

[MrStab]

yeah, a battery is needed. sorry, i didn't realise you wanted something passive. i can't confirm if the schematic is verified or not.

i had a look on the web, maybe this is more what you're looking for:
http://www.colomar.com/Shavano/cable_xlr_to_phone.html
(hey, seems to be from the same place as the other one!)

[PRR]

> a simple transformer.

Get a 12V:120V (or 24V:240V) power transformer.

Dynamic mike to the low-volt side. If a 3-pin plug, pin 3 can go to one end of the low-volt side, pins 1 and 2 go to ground, shield, and the other end of the low-volt side.

High-volt side to the guitar amp (or pedal).

Bass will be good, treble may be OK or dull.

Hum and buzz from the room may be very bad. Keep it FAR away from power wires and amp transformers. Any metal (even foil) around it will reduce buzz. Pure hum needs heavy iron, such as a short piece of iron pipe with two iron pipe-caps. You can also try a steel electrical junction box with steel cover. Drill the smallest possible holes for the jacks. (Don't try to drill for the 3-pin XLR jack, run shield mike cable out to a cord-jack.)

I've used such a thing once or twice. You are always better off with a proper audio transformer like CP8201. There's more than 20 bucks of work in finding a good transformer and a good shield.

[NBguitarist]

Can a passive DI be used in reverse when using guitar pedals for mic?
Or using a preamp before going into the pedal?

[ashcat_lt]

Can a passive DI be used in reverse when using guitar pedals for mic?

Yes, except the XLR jack is the wrong gender. 

Or using a preamp before going into the pedal?

This is frankly probably better.  It can be as simple as what Mr Stab posted or as fancy as you want.

[Mark Hammer]

There are two parts to using a voice mic with guitar pedals: impedance matching (which a transformer can do without battery or other power), and 2) level matching, which can sometimes be done with a transformer, but usually need an active/powered circuit.  "Mic" level is many db below what a guitar provides, so the signal needs to be brough up in level for best S/N ratio.

[therecordingart]

This question is in the top 5 technical questions we receive at work.

This isn't an impedance issue (assuming you are using a low-z dynamic mic like an SM58), but an issue of signal level and the sensitivity of the circuitry you are plugging into. To expand on what Mark said, the signal level of a dynamic mic is only a few millivolts unlike an electric guitar which can range from hundreds of millivolts to even a few volts peak to peak (EMG pickups come to mind).

For less than $20 I say get an "off the shelf" solution like the product you named or a Shure A85F.

[nap_alfa55]

Hi, look to  http://www.fennecelectronics.it/smf/index.php?topic=5088.0

[NBguitarist]

Can a passive DI be used in reverse when using guitar pedals for mic?

Yes, except the XLR jack is the wrong gender. 

Or using a preamp before going into the pedal?

This is frankly probably better.  It can be as simple as what Mr Stab posted or as fancy as you want.

So if the following circit will work
Seem easy for me to build one

http://hackaweek.com/hacks/?p=327

[digi2t]

This question is in the top 5 technical questions we receive at work.

This isn't an impedance issue (assuming you are using a low-z dynamic mic like an SM58), but an issue of signal level and the sensitivity of the circuitry you are plugging into. To expand on what Mark said, the signal level of a dynamic mic is only a few millivolts unlike an electric guitar which can range from hundreds of millivolts to even a few volts peak to peak (EMG pickups come to mind).

For less than $20 I say get an "off the shelf" solution like the product you named or a Shure A85F.

Wasn't this problem along the same lines as the Les Paul Recording guitar? Would the Shure A95U (or A95UF) work?

I know we're talking microphones here, I was just wondering.

[therecordingart]

This question is in the top 5 technical questions we receive at work.

This isn't an impedance issue (assuming you are using a low-z dynamic mic like an SM58), but an issue of signal level and the sensitivity of the circuitry you are plugging into. To expand on what Mark said, the signal level of a dynamic mic is only a few millivolts unlike an electric guitar which can range from hundreds of millivolts to even a few volts peak to peak (EMG pickups come to mind).

For less than $20 I say get an "off the shelf" solution like the product you named or a Shure A85F.

Wasn't this problem along the same lines as the Les Paul Recording guitar? Would the Shure A95U (or A95UF) work?

I know we're talking microphones here, I was just wondering.

I'm not familiar with the Les Paul recording guitar was it a low-z mic-level guitar? In the case of plugging a "regular" guitar into a mic preamp impedance IS an issue as the mic preamp is going to load the pickup. The A95U or similar device is the product you'll want, and I use one to plug my guitar into an X2u for a makeshift guitar-to-usb solution. You can calculate the amount of loss you'll get from plugging a guitar into a mic pre with this formula:

[ashcat_lt]

I'm not familiar with the Les Paul recording guitar was it a low-z mic-level guitar?

Yep.

In the case of plugging a "regular" guitar into a mic preamp impedance IS an issue as the mic preamp is going to load the pickup. The A95U or similar device is the product you'll want, and I use one to plug my guitar into an X2u for a makeshift guitar-to-usb solution. You can calculate the amount of loss you'll get from plugging a guitar into a mic pre with this formula:

Except that doesn't tell the whole story.  If it was just broadband attenuation, then we could just gain it back up.  It would add some noise, but might be okay.  The big problem is that the passive pickups are pretty big inductors, and the cable connecting them to the mic pre is a pretty big capacitor, and both of these cause high frequency content to drop off much faster than the lower frequencies.  That is, you have severe treble loss which can not really be undone with any acceptable results.