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Discussion Starter · #1 ·
After putting the system together, the right speaker plays normally and the left speaker puts out no sound unless the volume on the left side is increased greatly. Even then the sound on the left and right speakers are not even. I changed the speakers to see if it is the speaker that is the problem and the left speaker when input on the right side played normally. Hence, the speaker is not the problem. I changed the interconnets and that didn't make a difference. What can I do to further pinpoint the problem?


The equipment being used is the Onkyo PR-SC886 preamp, NAD T975 amp and Infinity Prelude MTS subs and towers. Just running 2 channel right now.


Any suggestions?
 

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I'm not sure about how you have things hooked up. Why list two pre-amps, unless you're running them in series for HT bypass? For now, simplify the signal path to one pre-amp driving a pair of amplifier channels, in turn powering a pair of speakers.


Good news is that with two of everything (pre-amps, line-level interconnects, amps, speaker wires, speakers) you should be able to move all these pieces around (like you did with speakers) in order to find where the problem lies. There are a total of 32 permutations here (2 ^5). But you only mention a problem with the Onkyo Pre-amp, so that brings us down to 16 permutations (2^4). First put tape lables on everything to keep track. Then just keep swapping line-level interconnects, amps, speaker wires, and speakers between channels until you have tried all the combinations.


Pre-amp 1 Amp L Ch Amp R Ch


Speaker 1

Speaker 2


The little table above shows one combination of line-level interconnects AND speaker wires. So you will have 4 of these little 2x2 tables:


A) L-L interconnect #1 on L Ch, L-L interconnect #2 on R Ch AND speaker wire #1 on L Ch, speaker wire #2 on R Ch

B) L-L interconnect #1 on R Ch, L-L interconnect #2 on L Ch AND speaker wire #1 on L Ch, speaker wire #2 on R Ch

C) L-L interconnect #1 on L Ch, L-L interconnect #2 on R Ch AND speaker wire #1 on R Ch, speaker wire #2 on L Ch

D) L-L interconnect #1 on R Ch, L-L interconnect #2 on L Ch AND speaker wire #1 on R Ch, speaker wire #2 on L Ch


Write down your results for each test in the tables above. When you are done, the culprit should be obvious. Actually you might see the pattern after a couple of tests. If not, post the results table here and someone will help. If the results on all tests are the same, the problem is the Pre-amp channel. You could confirm this by swapping to NAD pre-amp (if it's known good).
 

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The Village Idiot
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Combinations - permutations! Shades of college days and statistics classes!


Sounds like a logical approach to me.


Just one thing: The NAD T975 is an amplifier - not a preamplifier. I'd move the suspected offending channel output from the Onkyo to another channel of the amplifier and see if the sound problem moves with it. That could indicate a preamp problem - however I would make sure it wasn't source channel problems such as a 6 or 8 channel direct input source.


If the sound problem remains in the same channel with a different input channel from the preamp its an amp problem.
 

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Quote:
Originally Posted by mellamoesrico /forum/post/16974876


I'm not sure about how you have things hooked up. Why list two pre-amps, unless you're running them in series for HT bypass? For now, simplify the signal path to one pre-amp driving a pair of amplifier channels, in turn powering a pair of speakers.


Good news is that with two of everything (pre-amps, line-level interconnects, amps, speaker wires, speakers) you should be able to move all these pieces around (like you did with speakers) in order to find where the problem lies. There are a total of 32 permutations here (2 ^5). But you only mention a problem with the Onkyo Pre-amp, so that brings us down to 16 permutations (2^4). First put tape lables on everything to keep track. Then just keep swapping line-level interconnects, amps, speaker wires, and speakers between channels until you have tried all the combinations.


Pre-amp 1 Amp L Ch Amp R Ch


Speaker 1

Speaker 2


The little table above shows one combination of line-level interconnects AND speaker wires. So you will have 4 of these little 2x2 tables:


A) L-L interconnect #1 on L Ch, L-L interconnect #2 on R Ch AND speaker wire #1 on L Ch, speaker wire #2 on R Ch

B) L-L interconnect #1 on R Ch, L-L interconnect #2 on L Ch AND speaker wire #1 on L Ch, speaker wire #2 on R Ch

C) L-L interconnect #1 on L Ch, L-L interconnect #2 on R Ch AND speaker wire #1 on R Ch, speaker wire #2 on L Ch

D) L-L interconnect #1 on R Ch, L-L interconnect #2 on L Ch AND speaker wire #1 on R Ch, speaker wire #2 on L Ch


Write down your results for each test in the tables above. When you are done, the culprit should be obvious. Actually you might see the pattern after a couple of tests. If not, post the results table here and someone will help. If the results on all tests are the same, the problem is the Pre-amp channel. You could confirm this by swapping to NAD pre-amp (if it's known good).

I'm totally confused by the above
. Just swap the interconnects at the amp from L to R. If the problem stays in the left speaker it is the amp. If the problem moves to the right speaker it is the 886. No need for fancy tables or writing everything down
.


Bill
 

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Discussion Starter · #5 ·
I really made a mess of my original posting. I was so tired, crosseyed and frustrated when I posted my problem, it appears I should have waited until the next day. I made corrections to the original post and Bill Mac's suggestion makes a lot of sense.
 

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Sorry my first post sounded so confusing. I have thought some more about your problem.


The easiest thing to check is probably to double-check for proper connections at both ends of the preamp-to-amp interconnect cables. Also double-check for for proper connections at both ends of the speaker wires.


Assuming you have already done this, next I would check the channel trim (gain adjustment) for each speaker channel in the onkyo pre-amp's software. Just make sure all channel trims (gains) are set at zero for now (it should have zero's there by default, unless someone has changed them). If you have a video output connected to a TV or monitor, the on-screen GUI should be easier than trying to scroll though all the menus on the little LED faceplate on the pre-amp itself.


The NAD amp may also have individual channel gain adjustments to check. They would probably be a physical knob or pot instead of a software setting. If these adjustments exist, just make sure they are set the same.


As a very long shot (I don't have experience with either this amp or pre-amp) you might also check for a L/R channel 'balance' adjustment knob on the amp and on the pre-amp. The pre-amp might also have a balance adjustment in its software.


If the problem is still there, then check out the hardware. Very simply, swap the L&R speakers/wires/L-L cables to islolate the problem. Start at the speakers and work back towards the pre-amp.


First swap L&R speakers. If the quieter speaker changes places, then the problem is the speaker (the quiet one). If it stays the same, then swap L&R speaker wires at the speakers and at the amp (swap both ends). If the quiet speaker changes places, then the problem is the speaker wire. If it stays the same, then swap L&R interconnect cables at the amp and pre-amp (swap both ends). If the quiet speaker changes places, then the problem is the interconnect cable. If it stays the same, then swap L&R interconnect cables at the pre-amp only. If the quiet speaker changes places, then the problem is the pre-amp channel. If it still stays the same, then the problem must be the amp channel.


I think the paragraph above is a logically correct simplification of the complex procedure I mentioned in my first post. Simplified by removing redundant permutations. I believe this procedure should work, assuming that there is one and only one defective 'part'.
 

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Discussion Starter · #7 ·
Ding...ding...we have a winner. It was the left gain knob on the amp. Thank you for all your suggestions. The amp is so stinking heavy and so hard to reach in the back, I was missing the gains until I reached my hand back there and turned whatever I could. It was the gain and the speaker came to life. Thank you...Thank you...Thank you.
 

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Quote:
Originally Posted by mellamoesrico /forum/post/16984168



The NAD amp may also have individual channel gain adjustments to check. They would probably be a physical knob or pot instead of a software setting. If these adjustments exist, just make sure they are set the same.

Excellent suggestion and even better you were right on the money
! I would have never thought to see if the amp had seperate gain adjustments. Thats what is so great about this forum whether you are a new member or a long time member it is all about helping each other out when in need
.


Bill
 

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Great! You got it working, Snake. Glad to help. I bet you will like the Onkyo, that looks like a really nice pre-amp.


Thanks for the kudos, Bill. And I agree that forums like this are one of the best uses of the 'net that I have found.
 
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