Help required with simple? audio output stage

Thread Starter

philbowles2012

Joined Mar 28, 2013
42
What I would prefer, gents is to avoid a semantic debate about what the circuit I need is called, whether it will win "design of the year" or not nor whether its "pure" or "good enough" ...my original post is as clear as I can make it:

" I'm after a circuit that will get the most sound out of the speaker [3W 8ohm] without popping it and using the parts I already have, i.e. I don't wan't the complication of an op-amp etc - I'm not after fidelity or low distortion I want a loud noise to scare burglars "
 

Audioguru again

Joined Oct 21, 2019
1,779
Your "amplifier" is designed to turn a DC LED or DC motor on and off, not a loudspeaker that is designed for an AC audio input.
With your 12V supply and 8 ohm speaker then the maximum output power from a simple audio amplifier will be about 1.5W at low distortion or 2W at severe distortion. This is not loud unless the burglar carries the speaker in his hand.

Your circuit (when the capacitor is properly replaced with a resistor) drives the speaker with DC which might damage the speaker or reduce its loudness.

Isn't the siren IC obsolete? On the internet it was available 20 years ago in India.
 

TeeKay6

Joined Apr 20, 2019
572
What I would prefer, gents is to avoid a semantic debate about what the circuit I need is called, whether it will win "design of the year" or not nor whether its "pure" or "good enough" ...my original post is as clear as I can make it:

" I'm after a circuit that will get the most sound out of the speaker [3W 8ohm] without popping it and using the parts I already have, i.e. I don't wan't the complication of an op-amp etc - I'm not after fidelity or low distortion I want a loud noise to scare burglars "
@philbowles2012
Here's an example of what @DickCappels suggested:SimpleAmp.JPG
R and C values are not critical. You say that the output on pin3 of the UM3561 is only 1V peak, so I suggest Q1=2N2222 with R1=470. You have said the speaker is 3W and 5W in different posts; R3 can be used to limit speaker power. It is possible that a small heat sink may be needed for Q2 and Q3 depending on the value of R3.
 

Audioguru again

Joined Oct 21, 2019
1,779
The darlingtons produce a saturation voltage loss of typically 0.75V each (1V max) so the peak output will be 5V to 5.25V.
5V/8 ohms= 625mA x 5V= 3.125W. Loud enough to scare a burglar if he holds the speaker in his hands.
 

DickCappels

Joined Aug 21, 2008
6,542
The master has spoken. Maybe a rise in the power supply voltage is needed, in light of the anemic output current of the sound chip. More seriously, we are approaching the point where a test of the actual hardware will help determine if any further advances are needed.
 

TeeKay6

Joined Apr 20, 2019
572
The darlingtons produce a saturation voltage loss of typically 0.75V each (1V max) so the peak output will be 5V to 5.25V.
5V/8 ohms= 625mA x 5V= 3.125W. Loud enough to scare a burglar if he holds the speaker in his hands.
@Audioguru again
Of course you are correct; however the design also satisfies the TS's expressed desire in post#21. Moving from 3.125W to 5W (a figure that was seen in an earlier post) would raise the noise by 4.1db--noticeable but not greatly louder. I used 12V power because of TS's insistence that new parts be limited to what he has (whatever that means); the design could easily accommodate higher voltages (15VDC, 18VDC).
 
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