Fotios's microphone amplifier

[fotios]

This one i have construct for a Behringer ECM8000 but also includes a switch to cut the supply in Balanced input. Then may be used with dynamic microphone. Also it has stereo output - Pan Pot equiped - there is a photo and the schematic and pcb diagrams.

[fotios]

Here the layout

[fotios]

Here the layout in pdf. In the next page the schmatic.

[fotios]

Here the schematic in pdf

[impsick]

Foitos, your mic pre looks cool. Have you built this yet? How does it sound? Nice. I'd like to try builing this.

[fotios]

Originally posted by impsick
Foitos, your mic pre looks cool. Have you built this yet? How does it sound? Nice. I'd like to try builing this.

Look at this. The scheme comes from an application note from National Semiconductors for his LM833. This replaced from NE5532 with a slight modification in the subtractor (or balanced to single ended converter). The rest of circuit is simillar with those in proffesional audio mixing desks. This is quite visible from the power supply of +/-18Vdc instead the usual +/-15Vdc in conventional desks. Now this compo, it works fine with any type of condencer microphone if the phantom supply of 18V is satisfactory for it. In my case the Behringer ECM8000 works with 15Volts at least so it is fine. The sound quality it is pretty good and with slight modifications in the first stage gain, can used and as line input due to the input switch who cut the power in she. I have a set of oscilograms (as usuall with square pulses) and if you can to understand these you can estimate the quality of unit. Inform me if you want to i post these oscilograms.
Fotios

[fotios]

Originally posted by fotios
Here the schematic in pdf

In my schematic drawing, for simplicity the two presets PR4 and PR5 can be omitted and replaced by two resistors of 680Ù each. To add the posibilitty of cutting the power in the input XLR con1, so as we can making tests or connect a line level component or a dynamic mic, a toggle switch DPDT (Double Pole Double Touch) must be placed between pins 2 and 3 of con1 and the supply from PR4 and PR5 (or the two resistors of 680Ù insteed these).
Another item in this preamp is that; Great carreful needed during the adjustment of input sensitivity by VR5 to avoid clipping of signal because the extremely gain level of 101 in the first stage. In proffesional mixing desks offered a Clipping Led indicator in this stage. To add a such indicator in this preamp the only needed is a comparator between the signal level and the supply rails. In the next thread these additions.
Fotios

[impsick]

led clip light sounds interesting. can you show an example schema? would you be willing to share your eagle files?(if that is what you used)

[fotios]

Originally posted by impsick
led clip light sounds interesting. can you show an example schema? would you be willing to share your eagle files?(if that is what you used)

I use the EDWIN cad/cae (if i understand correct because your reference in "eagle" files) and if it so, we can interchange the whole project in GERBER.ASCII format. All cad/cae programs, can interchange between them projects under this general format. If you have the EAGLE cad/cae and are familiar with it, inform me to post the project in GERBER.
Fotios

[impsick]

yes i have eagle. post the gerber files if you can, that would be great! thanks.