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.
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.
And welcome to diyAudio 🙂
Remember to mix the signals (L and R) resistively first, don't just tie them together at the line level outputs.
And welcome to diyAudio 🙂
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.
Yes that's correct. I guess it's setup for connecting portable audio gear via common stereo 1/8" cable.
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.
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.
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?
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?
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.
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.
The resistors are important in order to mix the signals correctly.
JoJo1234, the lower the better, and this will be determined by your source output impedance that has to drive it.
There is no set rule, but if your source has a low output impedance say 1ohm-10ohm. then use a 1kohm pot.
If it has 100ohm to 1000ohm (1kohm) output impedance then use a 10kohm pot.
If it has a weak tube output stage, it could be 3kohms or even higher output impedance then use a 20k to 50k pot, but with this you will have to then factor in the amp load as well.
You want a ratio of at least 1:10 or even 1:100 you may not hear much difference between these two ratios, some say they can, but I'd like to see them do a blind test.
Cheers George
There is no set rule, but if your source has a low output impedance say 1ohm-10ohm. then use a 1kohm pot.
If it has 100ohm to 1000ohm (1kohm) output impedance then use a 10kohm pot.
If it has a weak tube output stage, it could be 3kohms or even higher output impedance then use a 20k to 50k pot, but with this you will have to then factor in the amp load as well.
You want a ratio of at least 1:10 or even 1:100 you may not hear much difference between these two ratios, some say they can, but I'd like to see them do a blind test.
Cheers George
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Thanks for the info. My source is a solid-state receiver's line level output jacks. From what I'm reading online, those usually have an output impedance of 100 Ohm or so, so I'll use a 10k Ohm pot.
Thanks again to both. I did some reading on line levels, including a Wiki article that states Y-splitters should not be used to combine two line out signals into a single line in because "Each line output would be driving the other line output as well as the intended input, again resulting in a much heavier load than designed for." So I'm starting to understand why I shouldn't just combine the two signals into one. With that, and assuming my powered speaker input is actively mixing the two channels correctly, can I use a dual ganged stereo pot without resistors for my volume control?
If you put the RCA -> jack plug in and measure the resistance between L & R you should find 2 of the wires are shorted (signal ground) and the other 2 (L & R signal) should show some resistance. If that is the case, then you can use the dual pot as you describe, there is provision for mixing.
If there is no mixing built in, then you will have to arrange some, as otherwise L & R will be shorted when the pot is at Max volume. You will be as well to use the mono arrangement, although you could feed it into both L & R.
If there is no mixing built in, then you will have to arrange some, as otherwise L & R will be shorted when the pot is at Max volume. You will be as well to use the mono arrangement, although you could feed it into both L & R.
You can use a dual pot, but the mixing effect will stop as the pot is turned up to full as CC mentions, because then the wipers, which will have to be shorted together to get you your single mono feed, will effectively be shorting the two input feeds together at full volume. Which if you never turn it up full isn't an issue.
I'm getting a little unsure what you actually want here 🙂
It is left and right audio with volume adjustment mixed into mono. So that means a single feed into your amp/speaker. Is that correct ?
So now with the info I've been given here, I'm wondering if the Jellybox speaker volume buttons don't work on the signal from my stereo line outs not because the input isn't a Bluetooth source, but because of mismatched impedance? (on the unit itself it says Line by the input, but the documentation refers to it as an Aux input). If that's the case, then putting resistors inbetween the 2 components would solve the issue, yes?
I doubt that tbh. Line and Aux are the same thing really meaning a "high level" input that would accept the output from a CD player etc.
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