Volume control in GC

[waltson]

I have just completed my GainClone from BrianGT's basic kit. I've installed an Alps 10k log pot to control the volume. Although it sounds great, I have one problem: I only have to turn the pot a couple of degrees from minimum until it's too loud.
Is there a way to modify the curve of the pot, so that the volume wouldn't get so high so fast?

Thanks

[jeff mai]

Originally posted by waltson

Is there a way to modify the curve of the pot, so that the volume wouldn't get so high so fast?

No - the problem is not the pot if it is correctly installed. Your system likely has too much gain. Try running without a preamp or other components between your CD player and the GC and see if that's better. If it isn't you may have wired something incorrectly.

[chipco3434]

Yup... the GC should run just fine with a CDP and no preamp. I have one like that.

[Upupa Epops]

You have probably wrong connected pot. This Alps have attenuation - 60 dB ( if is connected corectly ) and voltage of this GC is 33 times ( app. 450 mV input sensitivity ), so by normal conditions ( CD as sound source ) you get full power at app. " 12 o'clock ".

[waltson]

Originally posted by jeff mai


No - the problem is not the pot if it is correctly installed. Your system likely has too much gain. Try running without a preamp or other components between your CD player and the GC and see if that's better. If it isn't you may have wired something incorrectly.

There's nothing else between the CD-player and the GC, just the pot.
How do you decrease the gain? Was it the feedback resistor that sets the gain?

Thanks for helping

[jeff mai]

Originally posted by waltson
There's nothing else between the CD-player and the GC, just the pot.
How do you decrease the gain? Was it the feedback resistor that sets the gain?

1) The pot could be incorrectly wired. Check this first.

2) The feedback resistors sets the gain. If you're using a standard design, check that the resistors are in the right places.

3) Both channels? If yes, it is not likely to be a faulty part or an accidental wiring error. You could be misinterpreting the schematic or instructions.

[juniorsg73]

Watson,

Me too had similar problem with volume control.

The preamp I had is based on Pavel's Schematic with slight modification (OPA2134 and BUF 634). Preamp was hooked up to TDA7294.

I believed that the problem that we are seeing here is due to the gain setting. For my case, the gain of my preamp is 2 and the power amp (TDA 7294) is 33. Thus, in total of 66 (2x33) gain.

Guess the solution is to lower the gain in order to modify the curve of the vol. pot.

Hope that helps.......

[waltson]

Originally posted by jeff mai


1) The pot could be incorrectly wired. Check this first.

2) The feedback resistors sets the gain. If you're using a standard design, check that the resistors are in the right places.

3) Both channels? If yes, it is not likely to be a faulty part or an accidental wiring error. You could be misinterpreting the schematic or instructions.

Yes, both channels, so I don't think it's an accidental error either, but how wrong can one wire the pot? I've done it the way it's told in the GC kit user guide from chipamp.com: The center pin from the rca goes to pin 1 in the pot, pin 2 from pot goes to IN on the PCB, and the sleeve from the rca goes from pin 3 to SG on PCB. I don't think I've made any mistakes on the PCB, but I'll check that when I get home..

[carlmart]

Originally posted by waltson


Yes, both channels, so I don't think it's an accidental error either, but how wrong can one wire the pot? I've done it the way it's told in the GC kit user guide from chipamp.com: The center pin from the rca goes to pin 1 in the pot, pin 2 from pot goes to IN on the PCB, and the sleeve from the rca goes from pin 3 to SG on PCB. I don't think I've made any mistakes on the PCB, but I'll check that when I get home..

Instead of doing it by pin numbers, perhaps you should put the pot in the middle and check the pins with a DMM. The output pin should be half the pot's value. The other two can be reversed and the only thing that will change is the rotation direction. But it should work.


Carlos

[waltson]

Originally posted by carlmart


The output pin should be half the pot's value. The other two can be reversed and the only thing that will change is the rotation direction. But it should work.


Carlos

Problem solved!
Since I had a log pot, the curve is different on the two pins. When the pot is in the middle position, the value between pins 1 and 2 is app. 8k, and the value between pins 2 and 3 is app. 2k. So I just reversed the wiring and everything is good now!

Thanks for everybody for helping me