Hi I want to install a Potentiometer for Balance on my preamp. Could anyone tell me which is better
1#
I put the Balance before the Vol
2#
I put the Balance after the Vol
Which one is better ? Or have better way?
1#
I put the Balance before the Vol
2#
I put the Balance after the Vol
Which one is better ? Or have better way?
Hi, there are many ways, have a look at figure 9 on this page for an example of a very useful design Potentiometers (Beginners' Guide to Pots)
Your circuit #1 needs resistors in series with the inputs to work,
with each equal to about 10% of the balance pot's value.
http://sound.whsites.net/pots-f7.gif
Your circuit #2 loads the volume control's wiper and increases distortion.
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Both of those circuits are terrible. The first circuit will not even really work correctly. The second circuit is typical of consumer grade circuit but has some pitfalls.
Look at figure 3 here. ESP - Simple High Quality Hi-Fi Preamp Look at the volume and balance circuit. This is the circuit that works best, but it must be driven with a buffer - typical line level (tuner or CD output) won't drive it properly. The buffer must be capable of driving down to 1.5 K and have low DC offset so it can be direct coupled. The output should be buffered too and the buffer chip should be right on the same board as the volume control, right next to the potentiometer.
This is what I have found to be the "ultimate" analog volume/balance control (with credit going to Mr. Elliott). It circumvents all the bugaboos of conventional configurations. I build mine with Alps "Blue Velvet" potentiometer http://www.mouser.com/ProductDetail...MIo4fVjIr61AIVk0oNCh3x1QkVEAQYASABEgI2wPD_BwE but this is not mandatory.
If you use an audio taper potentiometer for the volume control, then skip R16 or replace it with a 1 meg resistor (last Hail Mary in case the pot wiper fails).
If this is all too elaborate then use your second circuit. Put the balance control as close as possible to the volume control and keep the leads as short as possible. Make the output leads from the wiper to the amplifier as short as possible. Even smallish stray capacitance can cause high frequency rolloff in this configuration, which is the big bugaboo of this configuration.
Look at figure 3 here. ESP - Simple High Quality Hi-Fi Preamp Look at the volume and balance circuit. This is the circuit that works best, but it must be driven with a buffer - typical line level (tuner or CD output) won't drive it properly. The buffer must be capable of driving down to 1.5 K and have low DC offset so it can be direct coupled. The output should be buffered too and the buffer chip should be right on the same board as the volume control, right next to the potentiometer.
This is what I have found to be the "ultimate" analog volume/balance control (with credit going to Mr. Elliott). It circumvents all the bugaboos of conventional configurations. I build mine with Alps "Blue Velvet" potentiometer http://www.mouser.com/ProductDetail...MIo4fVjIr61AIVk0oNCh3x1QkVEAQYASABEgI2wPD_BwE but this is not mandatory.
If you use an audio taper potentiometer for the volume control, then skip R16 or replace it with a 1 meg resistor (last Hail Mary in case the pot wiper fails).
If this is all too elaborate then use your second circuit. Put the balance control as close as possible to the volume control and keep the leads as short as possible. Make the output leads from the wiper to the amplifier as short as possible. Even smallish stray capacitance can cause high frequency rolloff in this configuration, which is the big bugaboo of this configuration.
Use a10K balance pot with 1.2K series resistor.
Using a 100K balance pot will allow your 100K volume control (it's in parallel with the balance pot, remember) to affect the precision of your circuit. It will work, but not as well.
Also, keeping resistor values lower will mitigate potential high frequency rolloff problems. Of course, the lower impedance circuit requires buffering.
It's always a juggling act to get it right.
And I also should point out that even using a 10K series resistor allows for a minimum input impedance of 10K, which is too low to be driven properly by some line level sources. These sources are typically designed to drive a 47K input impedance. Lowering this affects low frequency cutoff, which is further exacerbated by the fact that your circuit has variable input impedance.
Sticking with industry standard impedances ensures universal compatibility and provides predictable performance. An input buffer can easily provide this.
Sticking with industry standard impedances ensures universal compatibility and provides predictable performance. An input buffer can easily provide this.
My Chinese written language skills are nowhere near as good as your English 😉 but it appears that the values of your balance and volume pots differ.......? This will have a bearing on performance
Yes, that will be ok. There will be a loss of about 2dB, if your volume control is also 100k.
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Sorry for my written English😀
My balance and volume pots are 100K, and how to deceid the res value for the circuit?
The source are CD,DAC and phono amp(connected with LP) and the line stage is M7
This is the line stage
And this is the way I put the balance pots in according the advice
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What is the purpose of the switch? I don't think you want that.
For 100K balance pot, make R1=12K. I've never seen RL and RR before. I guess they help reduce interaction between the balance and volume pot? You might try a smaller value (4.7-12K?) for them. It's really better to separate the volume and balance resistor values by a decade, but that introduces other problems. I can't read Chinese, but I suspect that the pots in the circuit are much higher value - maybe 1 megohm? Your circuit won't work very well with 100K pots and the resistor values in your circuit.
Eliminate R16.
The circuit will introduce some attenuation. I'll let you figure that out.
Input impedance will vary from approximately 100K down to 12K. The lower value will only be when the balance control is all the turned all the way to one side. I sort of calculated the input impedance values in my head, so feel free to calculate a more exact range.
For 100K balance pot, make R1=12K. I've never seen RL and RR before. I guess they help reduce interaction between the balance and volume pot? You might try a smaller value (4.7-12K?) for them. It's really better to separate the volume and balance resistor values by a decade, but that introduces other problems. I can't read Chinese, but I suspect that the pots in the circuit are much higher value - maybe 1 megohm? Your circuit won't work very well with 100K pots and the resistor values in your circuit.
Eliminate R16.
The circuit will introduce some attenuation. I'll let you figure that out.
Input impedance will vary from approximately 100K down to 12K. The lower value will only be when the balance control is all the turned all the way to one side. I sort of calculated the input impedance values in my head, so feel free to calculate a more exact range.
RL and RR could be "fake log law" resistors, to turn lin pot log. Looks like he's gone with my link in post #2, sort of
You mean the switch that short the 400K res? It will helpful when used hi-sensitive speaker like 100db
You mean I need 1M for the balance pots?
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No, I changed your resistor values for 100K pots.
Your switchable resistor is going to change the way your circuit works. It will also increase the tendency for potential unwanted high frequency rolloff. You understand this, correct?
The switchable resistor is a very bad idea. I highly recommend you skip it.
The second circuit is found in a lot of consumer grade equipment. The balance control hanging off the volume control wiper mimics a "fake log" circuit.
Circuits like these do not belong in serious hi-fi design. They suck and are the "weak link" if everything else is up to snuff. That's why I started using buffered circuits with lower valued pots and resistors. High precision, no audible high frequency rolloff is the goal.
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