Would this potmeter work with a car audio line out?

In my boat I need a way to control line level to power amps volume, first to the subwoofers, but I will expand it to the two other power amps, to the front and rear speakers. The headunit sending out the line level signal is a Pioneer car audio headunit with nothing special, the subs are JBL marine 10" active, sealed subs and the two amps are Alpine and something I can't remember right now. But basically it works like any plain vanilla car audio stuff. The creator of CamillaDSP, @HenrikEnquist gave me the idea that I will go for, using stuff I know from before: A potmeter turned by an RC servo directly connected to it (I have a few ideas for that, it will be simple and totally reliable), controlled by an ESP32 (he actually said an Arduino, but I know ESPHome and didn't really need to learn Arduino, so I will use the servo library in ESPHome). The servo position will give me the position of the potmeter in degrees, which I can convert to a 0-10 or similar scale. That's not even the most important, the important is that I can hear that nothing is distorting.

So what kind of a potmeter should I use? I don't do advanced soldering, so I would prefer something either ready made or very easy. I found this on eBay:

https://www.ebay.co.uk/itm/144711214369

It's an ALPS, seemingly legit, RK27 A100K, so 100 ohm. It also has a PCB where the connections are easy, I can solder that without problems. It's like replacing keys on my Matias Ergo Pro Keyboard. Would that one do what I need? Or do I need a different resistance, like 50 ohm? I see that it says 2x 50, so maybe 50 is per channel. I know close to nothing about this stuff (somewhere between Manuel and Basil Fawlty) and hope somebody can help me, and that I gave the necessary information.

1687333570531.png
 
Last edited:
"It's an ALPS, seemingly legit, RK27 A100K, so 100 ohm. It also has a PCB where the connections are easy, I can solder that without problems. It's like replacing keys on my Matias Ergo Pro Keyboard. Would that one do what I need? Or do I need a different resistance, like 50 ohm? I see that it says 2x 50, so maybe 50 is per channel. I know close to nothing about this stuff (somewhere between Manuel and Basil Fawlty) and hope somebody can help me, and that I gave the necessary information."

I would say it is neither an ALPS nor 100R.
It looks to me like it is a copy, the font is wrong and stereo 50k with two of the contacts cut off. Plus they are supplied from Japan not China.

Active subs require a mono line input, not stereo. The human ear cannot detect stereo sub bass. All that happens is loss of bass in pockets as you walk around the room/area.
If you have a 50k potentiometer or indeed a voltage controller attenuator will be fine.
Beware of ground and power supply loops!
 
@JonSnell Electronic Goes to show how much I know... So where do you suggest I get the real stuff? As you understand this is not high-end, so if there's a well functioning cheaper potmeter I'm all for it.

And I forgot to say that there is a dual sub output from the headunit, and they have separate signals (but they are marked as Sub1 and Sub2, not left and right). That's why I thought a two channel pot was warranted.

As for ground loops and power supply loops that doesn't come into it here, the mechanical connection between the RC servo and the potmeter will be plastic, not metal.

@adason You're right, of course. Sorry.
 
Oh, I don't have seasons. I fish all year round. And I have had the power amps, one of the subs and the headunit for about eight years so far, in two different boats... It's all about how you protect them (I have been boating for close to 50 years, so I do know a bit about boats, but not potmeters). I use IP67 box lids for the power amps, and they are bolted to the aluminium under the dashboard, so they don't overheat. The headunit is in an IP68 marine enclosure.

Also the subs have different profiles for the crossovers in the menu of the headunit, so I think they must have different signal paths.

But then I'll order a few different pots and test them out, thanks!
 
Seems like you might be trying to do things the hard way.
What is it your trying to achieve ?
the amplifiers will have their own built in input level controls.
and the head unit will have front and rear outputs that can be adjusted by the units fader.
chances are the head unit might even have a third output for the subwoofer.
 
So you want to have remote control over various volume levels, from two separate locations.

I would suggest maybe something like motor driven pots.
Then you can use as many up/down switches in as many 'control' locations as you want.

All the sensitive low signal control can be placed in the best location.
And all the low voltage control wires can be run anywhere as needed.

Am I on the right track ?
 
Actually you're close! ;) But there are a few differencies:

I have around 10 ESP32's in the boat (I can run all lights including swiping with the searchlight, start the engine, tilt the engine, run the power block (used for pulling heavy chains of crawfish traps from a depth of 100 meters or so) and so on), so I will connect the physical switches to them. So one in the front and one under the dashboard will take commands from the physical switches and send the command signal via MQTT to the broker, and the ESP that does the job will get it from the broker. I don't know if you're familiar with MQTT/Mosquitto, but it's a lightweight system that is 100 % reliable and reacts almost instantly. Maybe a tenth of a second, probably less.

And the problem with motorized pots is that it is a bit more difficult to do a "go down 10 dB" on those, and other direct commands because the pot doesn't know where it is. It's possible (as another member of this forum pointed out) to do it with a stereo pot per channel, where I use an I2C ampmeter to measure the resistance and calculate that to a position of the potmeter. But by using a regular pot with the shaft hooked up to an RC servo controlled by the ESP32 I have full control, because the servo will understand commands like "goto 0 degrees", turning the pot directly to the mid position or "goto -180 degrees" to turn it all the way down and everything in between.