http://sound.westhost.com/pots.htm is an excellent article that covers all your questions and more.
As this thread is in a chip amp forum, I presume people are talking about using linear pots (law faking) with chip amps.
For some reason, I could never make it work properly at the input of NI amp. There was simple not enough control (in certain volume ranges) and it was not comparable with a good log pot. I'm talking here about control range and not sound quality.
For some reason, I could never make it work properly at the input of NI amp. There was simple not enough control (in certain volume ranges) and it was not comparable with a good log pot. I'm talking here about control range and not sound quality.
AudioFreak said:
I wouldn't be so sure about that, at least this is not a case with better quality pots.
Attached is the chart for all the standard taper types available with Nobel potentiometer. As you can see there are two different linear tapers available and 3 different log tapers.
Those characteristics are usually very accurate, and with mono pots (31 detents) I have no problem matching them to 0.5 dB (for two separate pots, on any given detent position).
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Mad_K said:
So, since my NI amp is already using 22k shunt resistor (input to ground) all I need to do is to add 100k linear pot in front of the amp (to take advantage of fake law principle). Is that correct?
Because if it is, it doesn't even come close to what a log pot offers (with regards to control range).
Ok im using BrianGT's NI kit. What is the purpose of the 22k shunt resistor R2 in the circuit?
If im using a log pot, then should this resistor be removed? Because from what i understand about fake lawing, you must place a resistor between input and ground pins, which is the exactly where the 22k shunt resistor is right now. So if i dont remove this resistor and i use a log pot, im I not fake-lawing a log pot? (which sounds ridiculous to me)
SO im very confused here. If someone could just clear up which of the following schematics are correct?
In my first schematic, this is the way i think a log pot should be used to control volume.
In my second schematic, this is the way i think a linear pot should be fake lawed to provide similar behaviour as schematic 1.
If im using a log pot, then should this resistor be removed? Because from what i understand about fake lawing, you must place a resistor between input and ground pins, which is the exactly where the 22k shunt resistor is right now. So if i dont remove this resistor and i use a log pot, im I not fake-lawing a log pot? (which sounds ridiculous to me)
SO im very confused here. If someone could just clear up which of the following schematics are correct?
In my first schematic, this is the way i think a log pot should be used to control volume.
In my second schematic, this is the way i think a linear pot should be fake lawed to provide similar behaviour as schematic 1.
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thanks thomas997.
i sat down for a couple of hours yesterday, and figured out what all the resistors do. this was pretty hard considering im no electronics expert. anyway, i made a spreadsheet that compares different fake lawing resistor values and came to the conclusion that the 1/20 ratio is the best.
as long as i maintain the same ratio between pot and fake law, i get the same volume curve. the only thing that changes is the input impedence range. which range should i tweak my values to? what is the safe, optimal range? i know that too low an impedence will overwork your source (right?) but what is the effect of too high an impedence?
i sat down for a couple of hours yesterday, and figured out what all the resistors do. this was pretty hard considering im no electronics expert. anyway, i made a spreadsheet that compares different fake lawing resistor values and came to the conclusion that the 1/20 ratio is the best.
as long as i maintain the same ratio between pot and fake law, i get the same volume curve. the only thing that changes is the input impedence range. which range should i tweak my values to? what is the safe, optimal range? i know that too low an impedence will overwork your source (right?) but what is the effect of too high an impedence?
If you are using 250k pot (or any pot that is more than 25k), R2 in the range of 22k, or similar, is neccessary to reduce input shunt resistance, otherwise the DC offset will be rather high (300mV or so).
You might use R1 or not, it's not really critical, with a pot I'm usually not using it.
You might use R1 or not, it's not really critical, with a pot I'm usually not using it.
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