Moderators: Dave Moll, Andrew Davie, Steve Anderson
Steve Anderson wrote:Well, OK, understood...but would you be willing to demonstrate it at a NBTVA convention as it is? (Assuming you could attend). You've done well, a credit to your programming skills, but I suggest taking it somewhat further as it only requires a bit more effort and the improvement will be worth it.
If you're still in the same field of 'real work' with submersibles it will help you there too. Really.
Steve A.
Steve Anderson wrote:Yes, normally a mechanical or 'wiper' type of control should be log for audio levels, all others, bass/treble etc are linear.
Klaas Robers wrote:Andrew, I see that the loudspeaker is now standing against a kind of box, where you have also screwed the display on. Can you not jigsaw a large circular hole in that box, somewhat more to the left, almost as large as the paper cone of the loudspeaker? Then you can screw the loudspeaker from the front into that hole, or from the back, if you like, such that there is NO SLIT between the chassis of the speaker and the wooden front of the box. So the fit should be air thight. You will see that you get much MORE sound and also better sound than what you have now. Don't bother what is behind the speaker. The table will be part of the baffle, it closes the front board at the bottom, and the top board in front of the disc also extends the baffle at the top.
What you do now is the worst thing that you can do. It is a pitty for the loudspeaker that you are using. This baffle will give you the best "amplifier" that you can think of. And it is free; cheaper than Ali Express ever.
Steve Anderson wrote:Certainly placing the speaker in a box like that will improve efficiency but the sound on male speech could become 'wooly' due to resonances in the somewhat flimsy box. But it's better than nothing.
The distortion may be simply you're overdriving the amp, the signal needs to be attenuated. If you replace the 'little filter' but change the values as follows...
Resistor between PWM output and input of the amp = 10k,
Capacitor from resistor/amp input junction to ground = 2n2,
Add 10k resistor across 2n2 cap.
This will do the filtering as before but attenuate the signal by a factor of two approximately. So for the same sound level you'll have to move the volume slider higher. If it's now too quiet adjust (reduce) the series resistor to 4k7. If it's still overdriving the amp increase it. You may have to fiddle around for a while.
As for it working without the filter it's probably the roll-off of the audio amp doing the same job, all the same I would put the filter back in.
Steve A.
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