Adding an internal mic
 

We get questions frequently here about how to add an internal mic. I just installed one, adding to an existing K&K setup, and tried to take some pictures along the way and describe the process. The writeup's probably longer than the actual process takes! But maybe it will answer some questions. Let me know if anything's not clear:

https://dougyoungguitar.com/blog

Thanks Doug, you remain the number 1 resources for all things 'acoustic plugged in tone.' Your pickup sample database is phenomenal.

I love the idea of the 1/8" input for easy switching out of pickup/mic options. I used to use UST/Mic two source pickups, sometimes with internal preamp, sometimes with external blender. For the last decade or so, I've gone single source for the simplicity and switched to SBTs.

But lately I'm itching to try the dual source again - SBT with Mag or SBT with Mic. Using the 1/8th" input is a great, simple way to try both.

Thanks for documenting that Doug. It'll come in handy down the road for a guitar I have in mind to work into the gigging rotation.

Doug,

Thanks for the writeup!

Questions: Have you compared performance of the Audix L5O mic when powered by 9V, to 48V? 48V phantom would of course require using all three conductors to the mic and different (or additional) jack(s) and cable(s)..., so not as elegant as your one stereo jack/cable solution, but curious as to possible mic performance differences...

Also, I've looked but failed to find the voltage output to the mic with the Sunnaudio Mic Power button engaged. Are you aware of the voltage, or might it be selectable to suit?

Thanks,

Lance

I wish this existed awhile back when I added a mic to mine. Super helpful resource.

I have not tried different voltages. My guess is that it doesn't matter much, since this is just a bias voltage. Perhaps it would affect headroom a little, but I really don't know. Generally, the unbalanced electret mics use the lower end of the voltage range. Some of the wireless body pack transmitters are only 5 volts, for example. I don't see any specs on Audix's transmitters for this. In any case, I've not had any problem with the sound quality when used with guitar preamps that are around 9 volts. I started using the Audix after seeing Laurence Juber using it, as a custom add-on to his Duncan MagMic, which I suspect delivers an even lower voltage to the mic. (I think I tried to measure that once, but I'm not recalling what it was)

The MS-2 manual says it provides Mic Bias of "8 to 14V in series with 3.3Kohms". I'm not sure what load the Audix mic provides, but this would seem to indicate somewhere in that range.

You certainly get stellar results wiring the mics as shown, so hard to argue with the procedure..

Thanks Doug!

Thanks Doug for a great write up for installing an internal mic.

You are correct, the MS-2 provides between 8-14V through a 3.3k Ohm bias resistor. We found this setting works for the majority of small condenser mics on the market.

We currently offer as an accessory to the MS-2, an Experimenter's Mic Kit. The purpose is to quickly and inexpensively demonstrate the capabilities of the Mid-Side (MS) decoder. We feel the ability to precisely place the mic anywhere in the guitar with our funny looking hand crafted mic holder dominates the results. Different mic placement allows adjustment to compliment the guitar, playing style, level of natural reverb and the MS image.

We are looking to expand the internal mic offering as a standalone product in the near future.

Based on Doug's Adding an Internal Mic blog and the link within about Powering Microphones, I decided to try this.

I bought a Shure WL50 lapel condenser mic for $30 off Reverb. This was a $200 mic back in the day, probably 10-15 years old... but in great shape and worth it to experiment with.

I decided to power it with my 9v pedal board supply, most of us have one of those. And I had a 10 mf cap and a 2k2 resistor in my stores.

I plugged it into my Helix just because it has a tuner/mute and volume control, just a straight through new preset. And it freakin' worked! I wasn't so much amazed than just excited at how simple it is.

Yes, the solder job is ugly, just a proof of principle. I plan to build a small 9v powered 1590 box that has 2 in's and 2 outs. The main pickup (TIP) will simply be a pass through and the 2nd source (RING) will have the 9v power and impedance applied to it.

https://i.imgur.com/gaBGxwz.jpg

https://i.imgur.com/Wn8yBCg.jpg

https://i.imgur.com/jY6DU4P.jpg

I started a new thread called DIY cheap 9v preamp for dual source MIC that takes the above wiring and makes a simple preamp box for it.

Felix 12 volts?
 

Hi,

I’ll admit that I don’t comprehend this completely, but i would like to give it a try anyway.

Would this work with a grace design Felix as well? It can output 12 volts on the tip or the ring. Is the bias resistor still necessary then? (Assuming it works in the same manner as the sunnaudio preamp?)

Felix already supports bias power for a mic, just like the sunnaudio does. So you don't need any special box, or even a resistor. Just make sure Felix is configured to supply the voltage on whatever input you are connecting the electret mic. rschultz is doing this because he's using a preamp that doesn't provide power for the mic.

Ah. That makes live easier . Thanks!