Problems with channel seperation

[jarros]

So, I'm finally wiring up my modded T-amp case as a part of a 2.1 system I'm making for my computer. Here are the schematics I drew up for the project:


Quick note as to what I changed: 3.5mm and RCA inputs (either/or, not both), headphone jack with headphone/speaker toggle, subwoofer output with volume control, and a secondary sub input as I will also be using the sub with a home theater system near the computer.

So far I've just done the wiring for the 3.5mm input to the volume control to the headphone output. The first thing I noticed is that 100K is too high for the volume pot (should be 50K). Secondly, I'm getting some crosstalk between the left and right channels. I disconnected the ground from the pot (so basically the ground is going from the input strait to the output) and the crosstalk is gone.

So do I even need to connect the ground to the volume pot? Any comments or suggestions would be appreciated!

Jared

[jarros]

Does anybody have any advice for a first time modder? I still can't figure out why adding the ground to the volume pot is making my stereo signal into a mono one.

Jared

[Pano]

Looking at you diagram, it's not the ground that's your problem, look at the sub connection - that's where the mono is coming from.

No Sorry, I misread your diagram. I'll look again

[Pano]

Hmmmm.... It's the X-Y thing that's got me confused. What is for?

Also, is the headphone jack the swithing type? Many are, so that signal is routed around tthe jack when it's empty. Miswiring?

[jarros]

Sorry, let me explain the X and Y thing:

"X" will be for my Subwoofer level control. The three R's are 10k resistors to sum the two channels into one mono channel, which then goes into a pot for the subwoofer level. This way I don't need a dual gang pot for the sub control, and it makes it easier at the end for the sub signal selector.

The reason I put "Y" in the diagram was to help compensate for the lower signal going to the sub, but now that I think of it I can just turn up the volume on the plate amp for the sub.

Keep in mind that I haven't introduced either of these to the circuit yet. I still only have input -> volume -> output.

Originally posted by panomaniac
Also, is the headphone jack the swithing type? Many are, so that signal is routed around tthe jack when it's empty. Miswiring?

Switching type as in it'll mute the speakers when headphones are plugged in? The ones I'm using aren't, but now that you mention it that might've been something to consider when designing this...

Jared

[dnsey]

Are you sure that the volume pot's wired correctly (it's not possible to be sure from your diagram)?
If the 'earthy' and 'output' connections were transposed, it would probably have the effect you describe at some settings of the control.

IN------|
******Z
******Z<---------OUT
******Z
EARTH--|----------EARTH

(ignore *s - they are just to format the diagram )

Hope that makes sense!

[jarros]

Originally posted by dnsey
Are you sure that the volume pot's wired correctly (it's not possible to be sure from your diagram)?
If the 'earthy' and 'output' connections were transposed, it would probably have the effect you describe at some settings of the control.

IN------|
******Z
******Z<---------OUT
******Z
EARTH--|----------EARTH

(ignore *s - they are just to format the diagram )

Hope that makes sense!

If you look at the pot head on from the shaft, there are two rows of leads (three leads in each row) and two leads on the bottom right (one for each channel). I understand that the leads on the bottom right are for some loudness circuit which I will not be using. For each row, from left to right, I have it wired Input - Output - Ground. I think this is what you have drawn in your schematic. If I had reversed the input and ground, wouldn't the pot just be backwards? i.e. turn it clockwise to lower the volume, counterclockwise to raise volume.

Jared

[jarros]

OK, I've been staring at this thing for the past hour or so and it's starting to get on my nerves. Right now I'm not totally concerned with the signals mixing, but I can't figure out why I'm not getting any volume until the last 10% of the volume control (where it increases rapidly). I did some googling and found this page. The original poster was having the same problem as me. He solved the problem by wiring the pot as per the diagram at the bottom of this page.

Isn't the diagram at the bottom of that page the suggesting the same wiring that I've been trying all this time? I've compared the drawing and my pot and they're exactly the same. What's going on? It's probably something simple that I'm missing, so somebody please help me!

Jared

[jarros]

I still can't figure this out, it's really holding my project back. I'm trying the volume pot with just one channel and it still is only giving me volume change at the last 10% of the pot. Once again, here's a diagram as to how I've wired it:


picture taken from www.bcae1.com

I have also tried 2 other pots, including the 50K pot that the T-Amp comes with. Can someone please help me?

Jared

[dnsey]

Yes, that looks OK.

I suggest that you disconnect eveything else, so that you're left with just what you've shown (for each channel), plus power supply and outputs. Check, then gradually build up the system again, testing at each stage.
You will probably discover that the ancillary stuff isn't wired quite as you think - it happens to all of us occasionally!