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My mistake I did not mention it. It is to be used in an SSB receiver, and the hiss is way above the 3KHz, so no problem to cut this off. But how? In the LM386 they do it by some feedback https://dmohankumar.files.wordpress.com/2015/03/hiss-free-lm-386-amplifier.png but I have no idea if this can be done in the LM383 as well.Hi,
You can hear this hiss, thus it is in the audible frequency range.
If you supress this hiss, you need to suppress audible frequencies.
The hiss is in the high frequency range, so you need a low pass filter to reduce the noise.
The lower the cutoff frequency of the filter, the less hiss you will hear.
But you will the miss the high frequencies when listen to music.
Reducing the hiss means to reduce the audio frequency range = to reduce audio quality.
--> if you want good audio quality, you should look for a low noise amplifier.
LM383 is not a good amplifier and I think it is not produced now, for many years...
Why use such an outdated IC?
Klaus
Instead you need an active lowpass filter to cut off hiss (and all the important consonant sounds of speech). When you remove all the s, t, f, sh, ch and other consonants then people listening will say, "What did you say, what did you say, over and over.
I did not understand. It is still the antique LM383 producing the hiss, not the SSB radio. You cannot filter the LM383 so throw it away and use a better newer audio power amplifier IC.
Your hiss problem might be caused by the speaker that might have a peak in its high frequency response. Try different speaker.
Good Luck removing radio interference from the SSB radio.
Yes you can but consider the values you need and the losses they would introduce. With such low impedance, you would be looking at R being a few Ohms and C being several uF, quite a lot of amplifier output would be sunk straight into the filterInstead of changing the circuit, can't I just add an RC LPF at the output (speaker side)?
You are not thinking that through... Lets assume a 5K stereo pot, at 100% volume you have no resistance between the top of the track and the wiper so you get maximum volume. Now back it off a few degrees, you get a slight drop in input signal from the first gang and maybe 100 Ohms in series with the loudspeaker, hence very little volume. Back it off a few degrees more and you get another slight drop in input level but maybe 500 Ohms in series with the speak, and almost no sound at all.I was also thinking of a stereo pot. one end connected to the input of the circuit, the other to the output (through coupling caps. Because the output would also be attenuated, the hiss would not be noticed at low volume levels. But can a standard stereo pot be used at a few W of output power this amp can provide?