well..... the amplifier i had is DIY, so currently it has no control over volume, so the volume will quite big on my ear (deaf ?) SO i would like to built and simple ones which located before the input stage ?
According to my knowledge, it is something like voltage divider, so what value should i use or any component addition to make it better ? (don't make it complicated)
My aim was to reserve the best of the quality, while have access to volume control.
( i heard something like don't build near the input stage, as inductance will effect the signal ?)
According to my knowledge, it is something like voltage divider, so what value should i use or any component addition to make it better ? (don't make it complicated)
My aim was to reserve the best of the quality, while have access to volume control.
( i heard something like don't build near the input stage, as inductance will effect the signal ?)
Have you thought of using a volume control? The value needs to be significantly greater than the output impedance of the previous stage, and somewhat smaller than the input impedance of the next stage.
aw... thats confusing...... i didn't though it was so confiscated ?
I thought there are universal volume control ? (or they are not good in quality ?)
well... the output impedance of previous stage is constantly different (because of change sources), but input impedance of next stage is easy though. (thats why they use pre-amp ?)
I thought there are universal volume control ? (or they are not good in quality ?)
well... the output impedance of previous stage is constantly different (because of change sources), but input impedance of next stage is easy though. (thats why they use pre-amp ?)
Use a simple potentiometer (adjustable voltage divider). The total value of the potentiometer should be high enough to keep from overloading your source and low enough to effectively 'feed' your amplifier. Perhaps an audio taper 20K device would serve...
hm... low means ? ( i though potentiometer's bottom value is 0 ?) THe source won't easily overload my amplifier, just overload my ears (maybe sometimes need for booming party) Well.... what i was asking, is what value is kinda nice for making the attenuation better (uniform and the volume is conpletely 0 when i JUST turn it to maximum)
A schematic diagram of the setting is welcome (easier for explanation ?)
A schematic diagram of the setting is welcome (easier for explanation ?)
A 20K pot should do it as others have said, this is basically a passive pre.
A potentiometer is just a vairiable resistor so at its minimum it will give you 20K of resistance in your signal path at its maximum it will give you zero resistance so you get your full volume that you have now its simple and works well with most power amps.
there is a down side that it does tend to roll off frequency extreams so a Buffer stage after it would correct that, but thats another story🙂
Alan
A potentiometer is just a vairiable resistor so at its minimum it will give you 20K of resistance in your signal path at its maximum it will give you zero resistance so you get your full volume that you have now its simple and works well with most power amps.
there is a down side that it does tend to roll off frequency extreams so a Buffer stage after it would correct that, but thats another story🙂
Alan
roll off frequency ? when and how ? (don't quite understand why potentiometer cause that) and what is a buffer stage ?
The amount of resistance presented to your source and the input of the amplifier will be variable when changing to position of the potentiometer. Since there is likely capacitor coupling present on one side, the other side or most likely both sides you will be basically creating a variable RC filter effect. For simplicity I wouldn't worry about it too much.
A buffer is simply an amplifier that has a gain of only 1 and just isolates or separates one part if the system from another.
A buffer is simply an amplifier that has a gain of only 1 and just isolates or separates one part if the system from another.
hm.... so it doesn't create much different to the output ? (roll off) well.... how much it effects and what extend it will cut off ? (any reference value of frequency it start roll off ?)
you mention for simplicity, you wouldn't worry, if i would want to avoid this problem, what can i do ? (example circuit ?)
you mention for simplicity, you wouldn't worry, if i would want to avoid this problem, what can i do ? (example circuit ?)
A volume control is not a circuit, it is a component. Otherwise known as a potentiometer. It controls volume by acting as a potential divider. There is plenty on the web about this. Just google the words you don't understand.
yeah, i know, but there are people said that it would cause roll off, so increase more component to compensate for it ? so its a circuit then ?
If you attach a long output cable to a high resistance pot then you can get HF loss at intermediate volume settings. Normally nothing to worry about. 20K pot with a metre of cable will be fine. If you are worried just put the pot at the output end of the cable.
Well when ever you have a capacitor feeding a resistor to ground (even a potentiometer used as a volume control), it forms a highpass filter where only frequencies above a certain range gets passed and frequencies approaching and below the cutoff point are attenuated....
The lower the resitance on that input the more current is required for any given voltage input by the source, (i.e. the harder it gets to drive , ohms law), going high brings with it the intrinsic noise of resistors called johnsons noise, which increases ase the resistance does.
So, as long as you stay between a load your source can handle, without going so high that you introduce noise at the input (which then gets amplified), everthing is the same. The potentiometer is just a voltage dividerm similar to 2 resistors in series, and there is no diffirence between one pot set to 50% attenuation and another with the same.
The lower the resitance on that input the more current is required for any given voltage input by the source, (i.e. the harder it gets to drive , ohms law), going high brings with it the intrinsic noise of resistors called johnsons noise, which increases ase the resistance does.
So, as long as you stay between a load your source can handle, without going so high that you introduce noise at the input (which then gets amplified), everthing is the same. The potentiometer is just a voltage dividerm similar to 2 resistors in series, and there is no diffirence between one pot set to 50% attenuation and another with the same.
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forr & DF96 - hm.... i thought the attenuation is before the amp (input) ? what would be the difference between located it between output and input ?
hm.... thank you for explaining to me, it seems it won't effect mine ? so since my amp can use direct source ? (no problem of johnson noise) the HIGH you mentioning is the current or load resistant ?
It is physicaly related to the resistance, a 10R resistor has less noise than a 10k resistor which has less noise than a 10meg resistor.
lets say your souce can drive with 1V, into 10R it would need to deliver 100mA (more than a couple of times the current a typical opamp would provide), 10k it only needs .1mA and with 1M even less...which is why they are used for very low current sources like guitar pickups.
lets say your souce can drive with 1V, into 10R it would need to deliver 100mA (more than a couple of times the current a typical opamp would provide), 10k it only needs .1mA and with 1M even less...which is why they are used for very low current sources like guitar pickups.
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You are stressing about it too much. The realistic effects of using a potentiometer to adjust input level aren't that big of a deal. If you need to provide some attenuation then you have to choose a method and using at potentiometer is almost certainly the best candidate for your purposes. Relax, add a 10K or 20k 'audio taper' potentiometer to the input and enjoy the newly added attenuator.
hm....... ok then, so..... how should i connect ? Pot have 3 legs, so we assume the leg A is the far left, then B is middle and right is C.
signal/hot to "A", then "B" to input to amp, "C" to ground/cold. I hope this is right ?
hm... i just use calculation and found out that no matter what value of potentiometer i use, then voltage of input is still the same ? (as long their position of knob is same) Then what is the different between high value or low value, such as 10k and 20k different ?
signal/hot to "A", then "B" to input to amp, "C" to ground/cold. I hope this is right ?
hm... i just use calculation and found out that no matter what value of potentiometer i use, then voltage of input is still the same ? (as long their position of knob is same) Then what is the different between high value or low value, such as 10k and 20k different ?
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There isn't much difference, that is why you shouldn't worry about it. You need to do some reading about potential dividers, and CR filters. Then you will understand how a volume control works, and what might go wrong under certain circumstances.
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