Audioguru has shown the simplest and the best way of varying the input signal level to the LM386 power amp IC.

However, reading between the lines I think you are talking about using a variable control voltage to change the amplitude of the oscillator, which is different altogether. For that you will have to use a VCA (voltage controlled amplifier). I believe we discussed that option in an earlier part of this thread, although in that context we were talking about using a voltage controlled waveform to modulate the oscillator?

Is that what you are intending?

 

Hi to all Thankyou for replies.

I tried attached ckts, one input is from PIC PWM, and other on/off. This ckt used to drive phezeo speaker, but I am using for speaker.
I tried LM386 audio amplifier(gain 20 and 200) to drive speaker with this ckt, volume is very low why?
So, I am planinng to build a ckt to converts PWM pulse of PIC into voltage(frequency to voltage converter) and oscillator ckt to drive speaker.. ..is it good idea or not?

 

Your circuit shows an LM358 low power opamp driving a low power piezo speaker not an LM386 power amplifier driving an 8 ohm speaker.
An LM358 low power opamp does not have enough output current to drive a low impedance speaker.

 

Your circuit shows an LM358 low power opamp driving a low power piezo speaker not an LM386 power amplifier driving an 8 ohm speaker.
An LM358 low power opamp does not have enough output current to drive a low impedance speaker.

Pardon me.. in bread board I used 24 Volt power supply and also I haven't showed LM386(5V seperate power rail) in simulation ckt.

And as I asked in my previous post, is it good idea to convert PWM signal in to voltage to control the volume and also oscillator ckt to drive the speaker all together?
Thankyou in advance.

 

I will not read 9 pages to try to figure out what you are trying to do.

 

I must be a bit daft, but I still can't understand exactly what you are trying to do?

Are you just using the PIC to create a variable duty cycle PWM waveform, which you then intend to intregrate, to create a variable DC level, which will then control the level of the oscillator output?

And then you intend to send that controlled level out to the input of an LM386 power amp.

Why? --Why not just use Audioguru's simple potentiometer approach?

Or are you intending to control the amplitude modulation of the oscillator automatically?

If you are intending to synthesize sounds, with variations of frequency, volume, harmonic content etc, then you would probably be better off starting with the analogue 'building blocks' of a music synthesiser:

Voltage controlled oscillator (VCO),
Voltage controlled filter (VCF),
Voltage controlled amplifier (VCA)
and envelope generators to control the above devices.

Then you can configure those blocks in whatever order you like, to experiment with sound synthesis.

A cheap and easy VCO can be found in a 4046 -
http://www.nxp.com/documents/data_sheet/74HC_HCT4046A_CNV.pdf

A VCA can be made using the gain elements in an SA571 -
http://www.datasheetcatalog.org/datasheet/philips/SA571.pdf
or perhaps adapting an LM13700 OTA -
http://www.national.com/mpf/LM/LM13700.html#Overview

A VCF is a bit more difficult -- the circuit here:
http://www.musicfromouterspace.com/analogsynth/vcf.html
gives you an idea of what's involved, for example.

Or are you intending something completely different?

 

I will not read 9 pages to try to figure out what you are trying to do.

Hmmm.. Sorry to post this project in previous thread, I did this because similar kind of project.. but different application..

I will start new thread..