Hi all,
I recently bought a new SS integrated amplifier and have noticed that the left channel plays significantly louder than the right. I used my Radio Shack SPL meter to measure the loudness from each channel while playing pink noise and measured a 5-6 dB difference between left and right channels.
I'd like to prove to the dealer and manufacturer that the amplifier is defective. Is there a second way of proving that there is a problem by measuring voltage/current on each channel? I would need help from the diyaudio community on how to conduct such a test and what sort of equipment is required.
Thank you,
George
I recently bought a new SS integrated amplifier and have noticed that the left channel plays significantly louder than the right. I used my Radio Shack SPL meter to measure the loudness from each channel while playing pink noise and measured a 5-6 dB difference between left and right channels.
I'd like to prove to the dealer and manufacturer that the amplifier is defective. Is there a second way of proving that there is a problem by measuring voltage/current on each channel? I would need help from the diyaudio community on how to conduct such a test and what sort of equipment is required.
Thank you,
George
George,
You need an AC voltmeter and a CD test track of 400Hz or so. Disconnect the speakers and monitor the AC voltage at the speaker outputs and note any differences. Exercise the volume and balance controls in between taking measurements.
A 6db difference means one channel would measure exactly half the other channel.
Good luck,
Dave.
You need an AC voltmeter and a CD test track of 400Hz or so. Disconnect the speakers and monitor the AC voltage at the speaker outputs and note any differences. Exercise the volume and balance controls in between taking measurements.
A 6db difference means one channel would measure exactly half the other channel.
Good luck,
Dave.
First verify that it is definitely the amplifier at fault. It could be a speaker or acoustics.
Swap the speaker leads in back of the amp left for right, and the problem should switch channels.
Swap the inputs left for right, and it should not switch channels.
If this really is an electrical problem, the dealer should be able to easily verify it.
Feed a mono signal into LR inputs (Y cord) and connect a loudspeaker between LR active speaker outputs.
Any channel imbalance will be readily apparent.
You can try music, pink/white noise or sinewave tone of variable frequency to pin down if the fault is broadband or frequency/amplitude dependent.
Dan.
Any channel imbalance will be readily apparent.
You can try music, pink/white noise or sinewave tone of variable frequency to pin down if the fault is broadband or frequency/amplitude dependent.
Dan.
George, you've got some great advice in the above posts. One thing to add, conventional volume controls can be poorly matched at low levels, this manifests as a sudden shift in image when turning down the volume. Worth checking.
Post #2 here has a couple of test tones you can burn to CD or whatever and use with any DVM
http://www.diyaudio.com/forums/mult...much-voltage-power-do-your-speakers-need.html
(An SPL meter is of no use in measuring something like this. In a typical room it is easily possible to almost to find points where sound at certain frequencies is reinforced or nulled, so much so in fact that on a continuous sine test tone of say around 400 to 2kHz you can often null the sound completely just by moving around the room. Move your head a few mm and the sound is back. So you need to measure this problem at the amplifier output to get a true result)
Post #2 here has a couple of test tones you can burn to CD or whatever and use with any DVM
http://www.diyaudio.com/forums/mult...much-voltage-power-do-your-speakers-need.html
(An SPL meter is of no use in measuring something like this. In a typical room it is easily possible to almost to find points where sound at certain frequencies is reinforced or nulled, so much so in fact that on a continuous sine test tone of say around 400 to 2kHz you can often null the sound completely just by moving around the room. Move your head a few mm and the sound is back. So you need to measure this problem at the amplifier output to get a true result)
Max Headroom,
I have a Y-cable and test tone/pink noise CD on hand. When you say "connect a loudspeaker between LR active speaker outputs" do you mean connect the speaker to the Left Channel positive and Right Channel negative and vice versa or simply connect one speaker to the left side and then swap to the right?
Thanks,
George
I have a Y-cable and test tone/pink noise CD on hand. When you say "connect a loudspeaker between LR active speaker outputs" do you mean connect the speaker to the Left Channel positive and Right Channel negative and vice versa or simply connect one speaker to the left side and then swap to the right?
Thanks,
George
Regarding the possibility that the fault lies within a different component and or speakers. I didn't want to preface my post with a lengthy read on what was tried in troubleshooting this issue but please believe that I tried swapping cables, sources, inputs on the amplifier etc and made sure that the balance control wasn't accidentally set to anything other than center.
With every test the left channel (or right when cables were swapped) played louder.
I will try the suggestions mentioned and report back.
With every test the left channel (or right when cables were swapped) played louder.
I will try the suggestions mentioned and report back.
Hi all,
Just finished some testing. Measured the voltage on each channel using a DMM set to AC voltage reading. The volume on the amp was set to just shy of the maximum setting.
I first tried playing some pink noise but that produced a voltage readout that varied. So I stuck with test tones to get a more stable readout.
At 1000hz:
Left channel = 34.7 v
Right channel = 34.5 v
At 500hz
Left channel = 33.9 v
Right channel = 33.8-33.9 v
At 300hz
Left channel = 33.7 v
Right channel = 33.9 v
Is the small discrepancy between channel voltages enough to cause the imbalance I'm hearing?
Just finished some testing. Measured the voltage on each channel using a DMM set to AC voltage reading. The volume on the amp was set to just shy of the maximum setting.
I first tried playing some pink noise but that produced a voltage readout that varied. So I stuck with test tones to get a more stable readout.
At 1000hz:
Left channel = 34.7 v
Right channel = 34.5 v
At 500hz
Left channel = 33.9 v
Right channel = 33.8-33.9 v
At 300hz
Left channel = 33.7 v
Right channel = 33.9 v
Is the small discrepancy between channel voltages enough to cause the imbalance I'm hearing?
No, you can't use a multi-meter in that way.
The post earlier by Rayma told you everything you need to do - it couldn't be any simpler.
This seems ok, those are very small differences. You seem to be hearing more like 3-10 dB differences.
Now repeat this at a more normal volume control setting. I'd not exceed more than a few volts output for safety.
You could be clipping the outputs. I presume that you have turned off the speakers for the test.
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Huh? You can't use a voltmeter to measure AC voltage?
Assuming he wasn't clipping the amplifier, George's test was perfectly valid. It seems his audible channel imbalance is probably elsewhere and not in the amplifier. However, as mentioned, it's a good idea to test at various volume control settings. But I don't think (possible) channel mistracking will even come close to the imbalance he's noted.
Dave.
Most multi-meters are only designed to work at pretty well mains frequencies, and NOT at higher audio ones - most also read DC voltages on the AC ranges as well, so if there's any DC bias where you're measuring the reading is meaningless.
I think you'll find most meters are good to 400Hz. That's why I recommended that frequency.
Based on his measurements in post #9, it would seem his meter is fine to 1000Hz. 🙂
Anyways, don't tell a poster looking for help you can't measure AC voltage with an AC voltmeter. At least without elaboration. My goodness.
Cheers,
Dave.
It's true that most budget DMMs are hard pushed for accuracy beyond a lousy 400 Hz but true RMS models, which are now quite common, are often specified to at least match audio bandwidth. A higher quality meter like UNI-T UT71E DMM for example, is specified for 100kHz bandwidth. Even their popular $50 UT61E model can reach a useful 10kHz at -3dB
The problem for many occasional DIYs is that they can't justify any instruments beyond the absolute basic and this makes suggestions hard for them to follow up on, not to mention affecting the credibility of measurements and the resulting confusion.
The problem for many occasional DIYs is that they can't justify any instruments beyond the absolute basic and this makes suggestions hard for them to follow up on, not to mention affecting the credibility of measurements and the resulting confusion.
Hi George.
I mean connect a single loudspeaker between the two red (positive) terminals.
With the speaker connected this way, you will hear only the difference between the two channels.
So, you can adjust volume, balance, bass and treble in order to diagnose the nature of the fault....ie simple channel gain mismatch, or frequency response mismatch.
It is common for the actual volume pot to channel mismatch, especially at low levels.
If you have only gain mismatch, the balance control will allow you to null the speaker output.
If you have a frequency response mismatch, a variable frequency tone will be helpful for diagnosis.
If you have more questions just ask.
Let us know what you find.
Dan.
Don't do this. Not only will this tell you nothing, but you run this risk of damaging the amp.
You need to try your test with the test tones at lower volume setting. Start near zero on the volume control. If you are not getting a stable reading turn it up slowly.
That said, if I just bought a new piece and thought I had a problem, I'd bring it back to the dealer to check out. Remember if you damage it, the warranty's shot.
I call BS.
When servicing gear I do exactly this routinely and no blow ups ever.
This is a quick and easy way for George to verify whether his new amp is faulty or not.
No DMMs or other test gear required.
The only caveat here is that the amp is not class D.
Dan.
Agreed, modern amps are well protected and even a complete goof couldn't do damage that way. It's virtually a bridgemode connection with only the amp+preamp channel difference as the speaker output - exactly what you want to get a grip on. Whether the dealer will understand that test as logically valid is another matter though. 'Not sure I would try to describe it to him/her.
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