Problems with channel seperation - diyAudio
Go Back   Home > Forums > Amplifiers > Class D

Class D Switching Power Amplifiers and Power D/A conversion

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 8th December 2005, 05:22 AM   #1
jarros is offline jarros  Canada
diyAudio Member
 
Join Date: Feb 2005
Location: BC, Canada
Default Problems with channel seperation

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:

Click the image to open in full size.
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
  Reply With Quote
Old 10th December 2005, 04:57 PM   #2
jarros is offline jarros  Canada
diyAudio Member
 
Join Date: Feb 2005
Location: BC, Canada
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
  Reply With Quote
Old 10th December 2005, 05:54 PM   #3
Pano is offline Pano  United States
diyAudio Moderator
 
Pano's Avatar
 
Join Date: Oct 2004
Location: Milliways
Blog Entries: 4
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
__________________
Take the Speaker Voltage Test!
  Reply With Quote
Old 10th December 2005, 06:04 PM   #4
Pano is offline Pano  United States
diyAudio Moderator
 
Pano's Avatar
 
Join Date: Oct 2004
Location: Milliways
Blog Entries: 4
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?
__________________
Take the Speaker Voltage Test!
  Reply With Quote
Old 10th December 2005, 06:33 PM   #5
jarros is offline jarros  Canada
diyAudio Member
 
Join Date: Feb 2005
Location: BC, Canada
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.

Quote:
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
  Reply With Quote
Old 10th December 2005, 07:02 PM   #6
dnsey is offline dnsey  United Kingdom
diyAudio Member
 
Join Date: Mar 2004
Location: Shropshire, England
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!
  Reply With Quote
Old 10th December 2005, 07:15 PM   #7
jarros is offline jarros  Canada
diyAudio Member
 
Join Date: Feb 2005
Location: BC, Canada
Quote:
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
  Reply With Quote
Old 20th December 2005, 02:21 AM   #8
jarros is offline jarros  Canada
diyAudio Member
 
Join Date: Feb 2005
Location: BC, Canada
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
  Reply With Quote
Old 28th December 2005, 06:44 PM   #9
jarros is offline jarros  Canada
diyAudio Member
 
Join Date: Feb 2005
Location: BC, Canada
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:

Click the image to open in full size.
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
  Reply With Quote
Old 28th December 2005, 06:52 PM   #10
dnsey is offline dnsey  United Kingdom
diyAudio Member
 
Join Date: Mar 2004
Location: Shropshire, England
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!
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
IRF P-Channel problems Rob Dingen Pass Labs 2 22nd December 2006 02:36 PM
2 Channel Amp problems wang_chi7 Car Audio 4 14th July 2006 08:09 AM
No Full Stereo Seperation ..???? xitronics Everything Else 2 7th July 2005 09:25 AM
3-channel gainclone complete, but problems... cowanrg Chip Amps 20 15th December 2003 07:04 AM
Mains seperation on PCB kiwi_abroad Solid State 15 15th October 2003 04:32 AM


New To Site? Need Help?

All times are GMT. The time now is 09:56 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2