audioguru Posted April 3, 2009 Report Share Posted April 3, 2009 A log potentiometer is a volume control.If you use a linear pot then most of the volume change will be at its low end and from half to max will make very little difference in volume. Quote Link to comment Share on other sites More sharing options...
ungastm Posted April 3, 2009 Report Share Posted April 3, 2009 i bought that linear pot because its hard to find that log potentiometer.if there is only a little difference maybe i'll should go to this linear pot.thanks sir! Quote Link to comment Share on other sites More sharing options...
audioguru Posted April 3, 2009 Author Report Share Posted April 3, 2009 There is a big difference if you use the wrong type of pot as a volume control.Steal a volume control log pot out of an old radio or cassette player. Quote Link to comment Share on other sites More sharing options...
ungastm Posted April 3, 2009 Report Share Posted April 3, 2009 oh..im very sorry sir..i'll find/steal a log pot for that..is it ok if i find a log pot from the range of 20k-30k? Quote Link to comment Share on other sites More sharing options...
audioguru Posted April 3, 2009 Author Report Share Posted April 3, 2009 The pot is supposed to be 22k. 20k to 50k will be fine and 10k and 100k might work. Quote Link to comment Share on other sites More sharing options...
ungastm Posted April 4, 2009 Report Share Posted April 4, 2009 what will be the effect if i use a linear potentiometer? Quote Link to comment Share on other sites More sharing options...
audioguru Posted April 4, 2009 Author Report Share Posted April 4, 2009 With a log pot, when the control is turned from max to half-way then the audio level drops -20dB so it sounds attenuated.With a linear pot turned from max to half-way the audio level drops only -6dB so it sounds almost the same.At the low end the log pot adjusts the low level volume.The linear pot suddenly switches the sound off then suddenly fairly loud. Quote Link to comment Share on other sites More sharing options...
ungastm Posted April 4, 2009 Report Share Posted April 4, 2009 it's not working sir, i used tda7052a and bc547b and for R7 i used the 22k carbon resistor instead of the trimmer. Quote Link to comment Share on other sites More sharing options...
audioguru Posted April 4, 2009 Author Report Share Posted April 4, 2009 R7 must be a potentiometer and is adjusted for a null in your voice that goes to your speaker. Your station's output audio amp is connected to its slider.Look at the datasheet for the TDA7052A to see how to connect its DC volume control at pin4.I think the gain is max (+35.5dB) when pin 4 has a low leakage 1uF capacitor to ground.The polarity of C4 is shown backwards. Quote Link to comment Share on other sites More sharing options...
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