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Geek Culture / electronics question about pots

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Phaelax
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Posted: 23rd Sep 2014 19:38
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So my audio setup in my Duster consists of a tiny amp that I've wired an audio input from an ipod. The amp is adjusted to be at the max volume I want allowed when the ipod is set at its max, and so the real listening volume in the car must be controlled by the ipod. I don't like this.

So what I think I wanna do is wire in a push-pull pot (to control front and rear) to the input before it reaches the amp. This would not only make it easier to adjust the volume from a good ol' fashion knob on the dashboard, but also save my ears when I forget the ipod's volume was way up.

I know I want a log pot and that "100k" has to do with resistance, but not entirely what part resistance plays in all this. Do I need a 500k for this? Something less? My only expertise in this area has only dealt with guitar wiring where I don't know why I need a certain one I just know I need this one wired to those pickups.

http://zimnox.com
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TheComet
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Posted: 23rd Sep 2014 19:56
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No idea what a "push-pull pot" is. Are you talking about a decoupling circuit/high pass filter?

If so then no, you don't need that for what you're trying to do. All you need is a dual potentiometer.

A good number to aim for is around 200 Ohms, since normal headphones are around 60-600 Ohms. You'll want the parallel resistance of the potentiometer and the audio input resistance to be equal to your ipod's output impedance.

Here's how you wire it:


Again, get a dual potentiometer so you can set the left and right channels using the same knob.

I like offending people. People who get offended should be offended. -- Linux Torvalds
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bitJericho
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Posted: 23rd Sep 2014 20:07
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Well I would just get a second amp tbh. A lot simpler. Then you can get an amp for your speakers that does the job properly.

For example, my home stereo goes from my PC, to my receiver, then out to my speakers and to my sub which has it's own amp. That's 3 amps but allows for very fine tuning of the levels.

I would do something similar in your case, perhaps a nice radio with an input jack for your ipod, that goes to your amp that goes to your speakers.

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Phaelax
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Posted: 24th Sep 2014 04:49
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I think you guys missed the point. There will be no stereo head unit. Not unless I wanted it to attach underneath the dash, or cut into the factor metal to make a DIN stereo fit. I think it's called a USA-230 size.

Push-pull pot is just like it sounds. It adjusts one level as normal, but if you pull on the knob it'll turn to adjust a different level. It's just a way to have two pots in a single control. Which sounds like a dual potentiometer to me. My guitar uses them to switch between active and passive electronics.

I want to use it to control not left and right, but front and rear. Since the car only has two 6x9s in the rear and only a single speaker in the front dash. (door speakers not possible in this car)

http://zimnox.com
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Dark Java Dude 64
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Posted: 24th Sep 2014 05:24 Edited at: 24th Sep 2014 05:27
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Hahaha, 'push pull' is a term commonly used in the field of electronics, and has nothing to do with potentiometers that can be mechanically pushed or pulled between two positions.

It's been like, two years since I have been interested in electronics, but I am pretty sure a dual pot isn't made of two different pots. Rather, a dual pot has one center terminal and two end terminals. As the knob is turned, resistance between one end terminal and the center terminal increases, while the resistance between the other end terminal and the same center terminal decreases.

Comet should be able to verify these statements.

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Phaelax
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Posted: 24th Sep 2014 05:26
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I get the term push-pull from working on guitars.
http://www.guitarcenter.com/DiMarzio-500K-Push-Pull-Pot-100024425-i1163659.gc

I'll look for a 250k at the store tomorrow.

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Dark Java Dude 64
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Posted: 24th Sep 2014 05:29
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Quote: "I get the term push-pull from working on guitars."
Indeed, I gathered that. I was just pointing out a discrepancy between electronics terminology and terminology from another field, in this case guitar.

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TheComet
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Posted: 24th Sep 2014 11:25
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Quote: "I want to use it to control not left and right, but front and rear. Since the car only has two 6x9s in the rear and only a single speaker in the front dash. "


You're confusing me. Do you have two channels or don't you have two channels?

The circuit and theory I described above applies to N number of channels so just tailor it to your needs.

I like offending people. People who get offended should be offended. -- Linux Torvalds
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Phaelax
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Posted: 25th Sep 2014 07:03
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The input is 2 channels going to a 4 channel amp. (which I should have bridged) The single front speaker however will contain both left and right channels.

http://zimnox.com
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Phaelax
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Posted: 25th Sep 2014 17:31
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Errr don't know why this didn't occur to me but I don't think my method is going to work. I don't think I can adjust two levels separately while at the same time still having both of them output at the same time through a single pot. Now thinking about it more, I believe this "push-pull" pot only allows a single source to pass through at a time, but I want both.

After furthering my education online over the subject, it looks like what I really want is a dual concentric pot. The knob will have to be different than what I wanted, but seems my only choice really.

http://zimnox.com
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bitJericho
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Posted: 25th Sep 2014 19:45
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You know a stereo will do all that right and you can get a nice one second hand for like 20 bucks right? lol. It doesn't have to go on the dash. You can put it on the ceiling or in the center console. You can put it wherever you like! I realize it's not as cool as installing a bunch of nobs but it does the job better.

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Phaelax
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Posted: 26th Sep 2014 00:05 Edited at: 26th Sep 2014 00:06
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On the ceiling? And there is no center console. This is the amp I'm using for its tiny size which fits neatly behind the dash.



http://zimnox.com

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Phaelax
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Posted: 26th Sep 2014 02:07 Edited at: 26th Sep 2014 02:07
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If someone can help me locate a decent stereo that fill fit with my drawing; Don't care if it has tape or CD, only two requirements are AM/FM and an auxiliary input (3.5mm). And the more 70s it looks the better.




http://zimnox.com

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