Issues amplifying signal

[Jorge Robles]

Hi!

First of all, I'm a n00b (on several aspects :P ), so be kind plz.

I'm building a mozzi based metronome, some kind of sequencer because the rhythms are somewhat special (flamenco ones!)

I´m using mozzi for the sound part and some nice neopixels to light it up, on a nano board and a cheap 8ohm speaker.

I've got big issues using a LM386 amplifier (a premade module).

The first one is that I cannot figure why the LM386 does not amplify the signal at all. I suppose I need to use some kind of DAC between the PWM pin and the amp. Actually the volume is the same no matter you touch the pot.

I tried with a RC circuit (10k resistor, 100 nF cap) found at http://www.avdweb.nl/arduino/hardware-interfacing/super-simple-dac.html, but it drags out the signal and becomes nearly mute.

The second issue is related to noise (electric one). I don't know why (again) the leds interfere with the speaker. And worst, I don't know how to fix it. The LM386 only amplifies the issue (pun intended) as I nearly converted my rig on a AM radio, seriously, I picked some walkie chat during tests.

Help, anyone?

Thanks!!

[Tarcisio León Drusin]

Did you used this schematic?
https://github.com/sensorium/Mozzi/wiki/Output-circuits,-filters,-amplifiers,-etc.-%28*-this-has-content%29
Also you need to enable "hi-fi mode" from a mozzi library file. Google that!

[Jorge Robles]

Sorry! I did not receive the notification.

Yes, I've built the filter+twin notch circuit this weekend and improved a lot, but It still is far from good. I will try to use the hifi mode.

The other issue, the weird whinning is now solved. I thought it was kind of electric noise, but was indeed a power shortage causing Nano to malfunction.  I solved using a fresh 9v battery. Doh!

[Tim Barrass]

Hi Jorge,

the latest output info is here:
http://mozzi-octopress.dev/Mozzi/learn/output/

You don't need/can't use an external DAC with Mozzi's PWM output, but you should be able to get reasonable output with an LM386, it has worked for me.  There are also some cheap digital amp modules on ebay which are very simple to use and work well.  You might need a decoupling capactior between your Arduino and the amp input, and possibly reduce the level with a trimpot to avoid overloading the amp input.

​

Tim

--
You received this message because you are subscribed to the Google Groups "Mozzi-users" group.
To unsubscribe from this group and stop receiving emails from it, send an email to mozzi-users...@googlegroups.com.
To post to this group, send email to mozzi...@googlegroups.com.

To view this discussion on the web, visit https://groups.google.com/d/msgid/mozzi-users/64ba7abd-abed-4ebf-b46a-3e63e3f40677%40googlegroups.com.

For more options, visit https://groups.google.com/d/optout.

[Tim Barrass]

Ah sorry here's the correct link https://sensorium.github.io/Mozzi/learn/output/

[Jorge Robles]

Thank you Tim!

Sorry for beign late. 

I´m sure I´m doing something wrong. 

I tested the LM on HIFI mode, with the SineWave HIFI example and the amplifier is doing quite well, but trying with the Bamboo sample, there's a very critical band where it sounds quietly fine. If I try to amplify, the signal simply disappear (I suppose is the overloading you mention).

I will try with the capacitor and the trimpot. Do I have to use the same circuit after the HIFI one?

Thanks!