what ohmage potentiometer for line out volume control? - diyAudio
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Old 15th December 2014, 05:41 PM   #1
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Default what ohmage potentiometer for line out volume control?

Hi, sorry for this really simple question, but I've looked around and can't seem to find an answer simple enough for me to understand. I have a little Jellybox powered speaker (for use with cellphones etc) with an Aux in. I connected it to my home stereo receiver's Tape Outs (line level) and it sounds great, but the volume buttons only work on Bluetooth sources, so I'd like to connect a potentiometer in between them to control the volume. Since it's a single speaker, I'll be merging the stereo's L/R outputs so as not to require a dual pot, and I think I understand the different curves... I'm just not sure what ohmage pot to choose. Thanks in advance.
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Old 15th December 2014, 05:48 PM   #2
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For line level use a pot in the 10k to 50k range should be ideal. You can add a single resistor to a linear pot in order to fake a log law if needed.

Remember to mix the signals (L and R) resistively first, don't just tie them together at the line level outputs.

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Old 15th December 2014, 08:58 PM   #3
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Remember to mix the signals (L and R) resistively first, don't just tie them together at the line level outputs.

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Thank you!!

I don't understand what you mean by "resistively" though. I was going to connect both Line Out L&R signal wires to the input pin, and both L&R output signal wires to the output pin; I figured this would basically be combining L&R channels into mono at the potentiometer, and connecting to both channels of the Aux In's stereo 1/8" jack... no good?

I was also trying to avoid using a dual ganged stereo pot, since my local Radio Shack store only stocks the single ones.
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Old 15th December 2014, 09:57 PM   #4
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It's a single speaker, but the aux in is stereo?
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Old 16th December 2014, 02:38 AM   #5
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It's a single speaker, but the aux in is stereo?
Yes that's correct. I guess it's setup for connecting portable audio gear via common stereo 1/8" cable.
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Old 16th December 2014, 03:12 AM   #6
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Are you sure that it's not 1/8 mono? If it's stereo it must be mixed internally unless the manufacturer is extraordinarily remiss. In which case you could feed L & R into the existing channels, attenuated with a dual pot, which would be the preferred option.

The problem is that if there's no mixing network then one channel is free to drive the other. So you need 2 identical res in series (say 2k2 each) across the outputs with the pot hot end (say 10k) connected to the midpoint of the resistors (and the cold end to signal ground) and the wiper and cold end of the pot connected to aux in L & R. Which is the mono pot solution you preferred.
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Old 16th December 2014, 07:46 AM   #7
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Like this. I've used 10k throughout. If the level is to low then reduce the two series 10k's
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Old 16th December 2014, 07:32 PM   #8
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Are you sure that it's not 1/8 mono? If it's stereo it must be mixed internally unless the manufacturer is extraordinarily remiss..
I plugged a connected a 2xRCA -> 1/8" stereo plug cable into it, and it worked with the source connected to either the L or R RCA... so that would mean the 1/8" jack is stereo, no?


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In which case you could feed L & R into the existing channels, attenuated with a dual pot, which would be the preferred option
Bear with me but I don't see why a dual pot would be necessary; if I used one of those 2xRCA -> 1xRCA "Y" cables to combine L&R channels into one mono channel, wouldn't that be the same as combining the L&R signal wires at the pot's input pin?
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Old 16th December 2014, 07:36 PM   #9
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Like this. I've used 10k throughout. If the level is to low then reduce the two series 10k's
Thanks for the info, but please bear with me, I'm a beginner at best (hope I didn't post to the wrong forum) -- are those 10k things resistors? That's kind of beyond me; I was hoping to accomplish a simple volume control with just a pot.
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Old 16th December 2014, 08:03 PM   #10
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Yes they are. Just common 10k's of 0.25w (or whatever small size you can get) The value isn't very critical, use what have or can get close to these such as 6k8 (6800 ohm) or 8k2 (8200 ohm).

The resistors are important in order to mix the signals correctly.
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