Some DIY-newbie questions (read and weep - or just laugh)
May 1, 2004 at 7:45 PM Thread Starter Post #1 of 7

luukas

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Ok.

This is absurdly simple for those with even the slightest amount of experience/training in electronics. What I'm puzzled about is a very simple 2xRCA -> stereo potentiometer -> 6.3mm output jack volume controller.

Firstly, I can't find the wiring instructions for a 6-pin alps potentiometer anywhere. I only know that the middle pins are for output.

Another thing that I am unfamiliar with is grounding. Since the wiring is RCA's -> pot inputs -> 6.3mm jack r/l channels, what part do the ground pins on the pot and 6.3mm jack play? Are they needed? If so, how should I wire them?

Sheesh, do I feel stupid now
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May 1, 2004 at 8:23 PM Post #2 of 7

ProFingerSk8er

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which pot are you using?
 
May 1, 2004 at 9:01 PM Post #3 of 7

luukas

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It's a cheap-o Alps 10k pot. Going to replace it with an Alps Blue or somesuch eventually, but those aren't really readily available around here.

Quote:

Originally Posted by ProFingerSk8er
which pot are you using?


 
May 1, 2004 at 9:33 PM Post #4 of 7

Megaptera

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Quote:

Since the wiring is RCA's -> pot inputs -> 6.3mm jack r/l channels, what part do the ground pins on the pot and 6.3mm jack play? Are they needed? If so, how should I wire them?


The ground pins are definitely necessary -- think of them as the reference point that your headphones will compare the l/r channels to. It's not as obvious on the RCAs, but they do have a place to connect to ground. If you think if the jack as having a shield on the outside and a hole inside where the plug's pin goes, the shield is ground. There will be a point for you to connect the ground hookup wire to. That goes to pot ground, and from pot ground, output jack ground. Make sense?

I'm afraid I can't help you much with the pot. If you know the model number or anything like that, google for its datasheet.
 
May 1, 2004 at 10:51 PM Post #5 of 7

luukas

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Ah, if only I had the part number - I've spent so much time looking for some type of schematic on Google it's not even funny anymore. But at least the grounding part is clear now, I thought it might work that way but wasn't sure
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Thanks.

Quote:

Originally Posted by Megaptera
I'm afraid I can't help you much with the pot. If you know the model number or anything like that, google for its datasheet.


 
May 1, 2004 at 10:56 PM Post #6 of 7

tangent

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If you get an electronics book (good plan) look up resistive voltage dividers. Two resistors in series across a voltage put out a fraction of that voltage at the midpoint of the divider.

All a pot is is an adjustable version of this same idea. The middle lug of each channel is the center point of that divider. The other two go to ground and to the input signal, to divide the input signal down. Which is which? Well, if you get it backwards, the volume will go down when you want it to go up! This isn't the end of the world, so experiment with it.

If you want to get it right the first time, use an ohmmeter to find out which of the outer lugs has less resistance to the center lug when you turn the shaft clockwise. That's the "input" lug.

Regarding grounding, all parts of the circuit -- the source, the volume adjuster circuit, and the headphones -- all have to agree on a common voltage against which everything else is referenced. Voltage is relative, not absolute, so there is no universal "ground". In several of the common headphone amps you'll see discussed here, they use a "virtual ground" which isn't the same thing as earth ground, and that might not be the same as signal ground from the circuits outside the amp. In a situation like this, it's necessary that all components agree on a common ground at their interface points.
 
May 2, 2004 at 10:07 AM Post #7 of 7

luukas

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Thanks Tangent. I just put it together and... it doesn't work. But I'm too lazy to see what's the problem right now
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