I had an old powered speaker the kind with base box and the 2 other speakers separate from the base and an old mic from a karaoke player.
So i decided to connect the mic direct to the speaker, with a pre-amp in between.
After much searching i decided to try this circuit in the picture. For one reason it is able to input both types of mic's. Electric the little ones you find in headset's and Dynamic the bigger ones that will work with a karaoke. Another reason it is simple and uses few parts. Stuff i already have.
Given it's simplicity this thing actually works quite well. The first mic i tried was an electric mic. You can see it in the pictures. It was from a broken computer headset. Worked but not great, acted sort of like a boom mic. The kind used in private airplanes and much feedback.
The second one i tried was from a broken karaoke player. WOW i powered everything up and it worked great, sounded great with no feedback. Worked like a P-A system should.
With that i removed any components not needed in the pre-amp. Basically the electric mic parts. Consisted of one resistor and two capacitors. That was not the best design decision. It will work like this, but those parts are need to be in there for best performance. So i re-installed the 2 caps and the resistor. Now its back to great.
This can be seen in action by clicking the video link below.
YouTube Video 1
Step 1: Mono to Stereo
Not really sure how much better it actually sounds with this installed, but in my mind it sounds better so we will just go with that.
It can be used in either direction. Stereo to mono or mono to stereo.
Step 2: Bread Boarded Circuit
In the end i did't use the volume control at the pre-amp.
I just relied on the main speaker volume.
Very few components for what it does. 7 components including the LED. Mine actually has eight. I used two 100K resistors instead of the 220K it calls for.
- 1) 4K7 ohm
- 1) 220k ohm
- 1) 2k2 ohm
- 1) 120 ohm
- 3) 600 ohm
- 4) 10uF
- 1) 100uF
Step 3: PCB
So after some investigation i found i had gotten the output capacitor in backwards.
After fixing that it was running great.
Step 4: Non Altoids Tin
Step 5: Install and Get Power
I decide i would go ahead and assemble everything and try it.
It is put together and working as can be seen in the video.
As soon as i get irritated enough with the overdrive issue i will go back in and drop the voltage to 5v
Thanks for looking!