Use another audio amplifier (LM386(?)) with the Propeller.

T&E Engineer · 2006-07-21 16:55

I am trying to build something close to what is designed into the Propeller Demo Board - Rev C schematic.·I have most of everything in place and working except for the microphone section and Headphone amplifier section.

Has anyone thought about using another audio amplifier such as an LM386 (as taken from the Professional Development Board schematic) and tried this on the Propeller. I understand that the LM386 wont work off of 3.3 volts but I still have 5v available for the mouse/keyboard section so this may be ok.

I just don't want to have to place an order with Jameco or Mouser for the MAX4411ETP if I have plenty of LM386 ICs from Radio Shack.

Also I hope that a Radio Shack Electret Mic can be used to recreate the schematic mic.

Comments?

Mike Green · 2006-07-21 17:19

The LM386 is only one channel. You could use two of them.

T&E Engineer · 2006-07-22 18:54

I would like to use the LM386 audio amplifier on the Professional Development Board into P10 or P11 on the Propeller. However, all I see to test the audio is the program (Microphone_to_Headphones.spin). I don't see where it knows to use P10 or P11 for the output. All it sugests is P8 and P0 for the ADC and DAC. Does this make sense?

Any other programs to test out the Audio. Will the LM386 audio amplifier on the professional development board even work?

Comments.

T&E Engineer · 2006-07-22 19:35

I see in the Assembly routine the pins 8,9 for the mic and 10,11 for the audio outputs now (It would have been nice to have commented that better). Anyway, I did not have a 1 nF (0.001 uf) but used a 0.010 uf instead going to the Professional development board Audio Amplifier X7 connection. I was able to scratch my finger across the mic and did hear it (not too loud) via the piezo speaker (default) on the audio amp circuit on the Professional Development Board. I tried an 8 ohm speaker too and it was a little louder but not great. I could not distinquish my voice though if speaking into the electret mic from Radio Shack.

I would still like to know if there are any other audio programs developed for the propeller.

Comments?

acantostega · 2006-07-22 22:36

I was wondering the same thing! I have a ton of LM386's, some for audio, some for simplistic BEAM bots (see Herbie 'bots) [noparse]:)[/noparse]
By the way looks like Jameco doesn't carry the MAX411. Does it even exist in a DIP form factor?
Please let us know if you get stuff to work.