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Old 2nd May 2017, 01:29 PM   #1
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Default Channel imbalance drives me crazy

Hi all,
i always thought that my room acoustics affect the stereo imaging when listening to music (right speaker louder than left) until a friend popped in and said that something must be wrong with either the speakers or the amplifier.

After source,speaker,cabling etc swapping we found the problem is with the amplifier.
I fed the input source with 1Khz test tone and set the gain at 1V rms on the speaker outputs.
Left output reads 0.8V and right 1V (no speakers connected).
When i swap the speaker cables on the back of the amplifier the weak speaker sounds louder of course.
I checked everything (capacitors/resistors/bad joints,swapped power amplifier boards, sprayed the volume pot) - everything is ok, the amp is in mint condition.
I believe the problem is somewhere in the pre-amp stage( iruled out the power stage as i used the boards from the power amplifier that i also have and they are identical) or a faulty alps pot

I'm talking about a Roksan Kandy KA1-MK3 amplifier, Roksan asks 199 to repair it plus materials which i find it ridiculous and no way to get any schematics from them.

Find attached some photos and please help before i go crazy.

Thanks

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Preamp
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Power amp
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Volume Pot
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Old 2nd May 2017, 01:34 PM   #2
basi is offline basi  Croatia
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And the oscar goes to Volume pot.
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Less is more!!!
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Old 2nd May 2017, 01:40 PM   #3
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Quote:
Originally Posted by basi View Post
And the oscar goes to Volume pot.
No kidding
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Old 2nd May 2017, 01:44 PM   #4
srinath is offline srinath  United States
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I have a carver M200 that is this way.
And sadly no volume pot to blame on it.
I've swapped drivers and pre drivers left to right and the problem does not change sides.
Anyway you may have a volume pot issue - hope it works for you.
Cool.
Srinath.
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Old 2nd May 2017, 01:52 PM   #5
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When i adjust the knob the 0.2V difference between the channels gets even higher, it doesn't remain the same at higher gain.

The 7805 voltage regulator gets hot (60C) but i reckon this is normal, otherwise i would have other issues wouldn't i?
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Old 2nd May 2017, 01:59 PM   #6
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Btw, i'm currently feeding the power amplifier from my DAC.Did the same test and the output on both channels is 1V rms.It's like i got my hearing back,lol

Time to fix the integrated
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Old 2nd May 2017, 02:04 PM   #7
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Quote:
Originally Posted by misfits73 View Post
Hi all,
i always thought that my room acoustics affect the stereo imaging when listening to music (right speaker louder than left) until a friend popped in and said that something must be wrong with either the speakers or the amplifier.
So, it's always been like that?
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Old 2nd May 2017, 02:05 PM   #8
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Quote:
Originally Posted by misfits73 View Post
Btw, i'm currently feeding the power amplifier from my DAC.Did the same test and the output on both channels is 1V rms.It's like i got my hearing back,lol

Time to fix the integrated
Did you use DeOxit on the volume pot?
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Old 2nd May 2017, 02:13 PM   #9
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DC Offset measured 4mV and 21mV.
Don't know how much to set the bias current but i used the power modules from the power amplifier and it didnt make any difference.
The bias and DC offset are measured the same on the integrated and the power amp.
No bad joints, cracks etc

Here is a photo of the power amp (i bought it for biamping):

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Old 2nd May 2017, 02:14 PM   #10
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Originally Posted by scottjoplin View Post
So, it's always been like that?
Yes but i blamed my room for that
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