Arjen´s TA2020 board: 1 channel into amp 2 channels on spekaers - WHY ? - diyAudio
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Old 18th August 2010, 04:10 AM   #1
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Default Arjen´s TA2020 board: 1 channel into amp 2 channels on spekaers - WHY ?

Hi everybody,

if I could one day bring these boards from Arjen without complication to work - that would be really fine: tubebuffer amp V2 and TA2020 MkIII

After I cleared this speaker relay issue I also could stop this persistent noise out from the speakers. So far so good.

Two main questions are open for me:
1) when I connect the tube buffer to the TA2020 board I listen out a powerless and scratchy sound. Using the TA2020 board without the buffer amp the sound is much undistorted and cleaner. Arjen told me that a bad tube could be a reason. Sadly I have no other tube to compare. Can this be ? I can remember that in the beginning the sound even with the tube was not so distorted like now.

2) I wanted to checkup if the channel outs from CD-player match well with the speakers out. So I made the usual channel test with one rca socket in the player plugged in. I expected one speaker sounding but I listened from both speakers ...even with a bit higher vol. ?? How can this be ? I connected the player this time directly with the TA2020 board. My player has an adjustable vol. out. How can the channel separation be influenced and what solutions are there ...?


Thanks for your attention
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Old 18th August 2010, 12:11 PM   #2
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Does the TA2020 amp play sound through both speakers with only one RCA input connected directly from the player?? If this is the case, you are getting a blended signal when both RCA's are connected, not true stereo. Not good. Have you checked the board to make sure the signal paths are isolated from each other?
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Old 18th August 2010, 05:04 PM   #3
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Stupid question: How can I check the signal paths ? I see no wires in contact which shouldn´t be in contact.
I suspect the speaker relay board which is added into the board lately ... Should I check up the version without the relay board ? Or are these +/- speakerwires laying on each other the reason ? I made a pic - see please:
Attached Images
File Type: jpg TA2020pic.JPG (592.5 KB, 174 views)
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Old 19th August 2010, 12:37 AM   #4
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Default Issue 2) cleared

Meanwhile the 1 channel in 2 channel out issue is cleared. What I have did ?
I removed the white plastic insulation and laid the two cables open. Further I removed the buffer amp away which was laying with the cables around the power board... maybe these wires acted like antennas or something similar.

When I powered the amp the hiss/noise became much more silent. This was what I had expected from a battery as power source. And testing one channel from player resulted finally in one channel speaker sounding

--------
Only 1 concern open ...
If I knew if a fault tube is the main reason for the distorted sound of the buffer amp (like in issue 1) explained)
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Old 19th August 2010, 12:57 AM   #5
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I suspect, unless wires were physically touching, that the signal was being induced by the wires laying on one another or on the buffer board. Did you hook the buffer back up and all is well?
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Old 19th August 2010, 03:42 AM   #6
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No. But to make it clear: the buffer amp wasn´t hooked up with the power board when the channel problem appeared. The buffer amp was just laying closed to the board with it´s long "spaghettis". I just placed the buffer amp far away in addition to the wire order on the speaker outs.
When you ask if I placed the buffer amp again closed to the poweramp: No.
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Old 19th August 2010, 09:11 AM   #7
teamacc is offline teamacc  Netherlands
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It seems to me you wired the channels the wrong way: The blue wire is "top" at the amp board, but "bottom" at the other board.
This means that one speaker saw the negative sound production, (that is the speaker on the "working" channel), and the other saw the positive sound production. (not-connected side).

So basically: you had the blue/brown wire wired wrong. The removal of the insulation did not do anything, but only made you reconnect it right.
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Old 19th August 2010, 09:27 AM   #8
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The wiring is correct on the amp according to the pictures found here. I can not see the delay board clearly enough, but it appears to wrong with both positive leads entering and it clearly shows OUT - and OUT + leaving the board. Looks like the signals are combined there. But I would need a better view of the board to make sure.
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Old 19th August 2010, 09:58 AM   #9
teamacc is offline teamacc  Netherlands
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Seems to me like the following has happened:
Click here for an image

The non-used side (lets say its the right), has both outputs (+ and -) at around 1/2 of the supply voltage. (6v)
The used side, has on max sinus, the - on 0v and the + on 12v

Wired this way, the left speaker gets a positive input of the right side, at 6v, and a negative of 0v.
The right speaker gets a positive input of 12v, and a negative of 6v.
Both speakers will see the same voltage difference, hence, reproduce the same sound.
They will both make less sound too.
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Old 19th August 2010, 10:03 AM   #10
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I see. So when you switch the brown and blue wires on the "protect" board, all should be well, right?
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