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Old 31st May 2013, 05:04 PM   #1
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Default Installing On/Off switch and Volume knob?

I am thinking about buying one of these

MKLL Tripath TA2024 Amplifier Board 2X15WATT Tested New | eBay

I am wanting to install a volume knob as well as an on/off switch. I assume I can hardwire into the board but not sure where since there isn't much of a schematic provided. Thanks in advance!
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Old 31st May 2013, 05:07 PM   #2
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Power on/off switch goes in between the 12V input and the power supply and the volume pot has ground on the left pin pair, audio output to the amp on the center pair and audio input on the right pair(seen from the shaft end/front of the pot with the pins/legs facing downward)
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Old 31st May 2013, 06:09 PM   #3
Mooly is offline Mooly  United Kingdom
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Post #46 illustrates Tekkos' description on the pot

Simple stereo gain stage
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Old 1st June 2013, 03:34 AM   #4
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Tekko and of course the great Mooly thanks for the response!

Would this be the right potentiometer?
500K Ohm Linear Dual Taper Rotary Potentiometers B500K 500KB Pot Alpha | eBay

I see that there are many different options when it comes to the OHMS. Just not sure which one I should order up for my project.

Thanks again in advance!
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Old 1st June 2013, 06:13 AM   #5
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A lower value would be much better in practice.

500K would "interact" with the input impedance of the amp causing such issues as poor "feel" where the control might appear to do little until turned right up and also reducing the high frequencies as it forms a simple R/C filter with the ever present input capacitance of the amp.

Go for somewhere between 10K and 50K.
You can also use a linear pot and add a resistor to fake the log law. Explained well here, look at "changing the law of a pot"
Potentiometers (Beginners' Guide to Pots)
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Old 1st June 2013, 06:21 AM   #6
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Mooly,
Thanks so much, you are the best! I have been researching since I posted my question and found that the 500K wouldnt work very well. I found a couple of spots where it mentioned 50K. Do you think buying several different pots in the 10-50 range would be a good idea, or just go for the 50?
Thanks
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Old 1st June 2013, 06:25 AM   #7
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BTW, thank you for the link....

I never knew there was so much to learn about pots. Back to reading.
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Old 1st June 2013, 06:30 AM   #8
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You're welcome

Common values are 10K, 22K and 47K or 50K. Personally, for an amp used with modern sources (CD etc) I would go for 10K or 22K but any of those values listed will work just fine.
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Old 1st June 2013, 06:50 AM   #9
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Just finished my homework for the day, now my brain hurts . After reading through everything I am thinking the 10K might be the best. My main source is going to be an iphone. Maybe I will jut buy one of each, 10K and 22K.

Thanks again Mooly!
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Old 1st June 2013, 07:02 AM   #10
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10K is fine.

Some more info... some portable sources, Ipods/MP3 players etc etc (as opposed to normal separate hifi components) use a small Class D stage as the headphone/line output. Some of these sources don't work well in high impedance loads (such as a volume control) because they rely on the low impedance of the h/phones to form part of the output filter. It's not all, just some players. All you can do is try and test. If there is a problem then the cure is easy, you fit a low value resistor such as 33 ohms across the inputs (left and right). You probably won't have a problem but just worth mentioning if you do.
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