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SBM

Left and Right channel

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Hi Guys , 

I am using a vintage Rotel integrated amplifier to power by stereo speakers and noticed that one channel is 10db louder than the other.

 

Is that because of the amplifier is old?

Using the same speaker cables on left and  right speakers. Connected via mobile using the RCA cable.

 

Attached the measurements using the db meter. It's approximate only.

 

Thanks

Screenshot_2020-03-21-21-14-59-22.png

IMG_20200321_211636.jpg

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Are you measuring using bandwidth limited  pink noise?AVR internal test tones?

Is  the mic the EXACT same distance from each speaker?

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Do not touch the volume control Swap the left/right Input to the amp and play the same track and measure again

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10dB will be audiable, you can hear the difference but wanted to quantify??? Check your test procedure as above. What model RA-xxx amp? Does it have PRE-OUT/MAIN-IN RCA connectors at rear, if so plug your phone (at minimum volume) into the MAIN-IN's and check for balance. Alst test the preamp by crossing the PRE-OUTs to MAIN-IN with RCA cables, ie, Left PRE-OUT to Right MAIN-IN, Right PRE-OUT to Left MAIN-IN, still same channel louder etc...

 

Most probably a dirty switch or contact issue. Apply gentle pressure to each switch in turn, rock slightly back and forward, then fully switch, any impact? Could also be dirty protection relay...

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3 hours ago, jamiebosco said:

Are you measuring using bandwidth limited  pink noise?AVR internal test tones?

Is  the mic the EXACT same distance from each speaker?

Hi mate, it's very approximate measurements only. Tested using the sound meter app. And tested almost close to the speaker at the same distance and volume. 

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2 hours ago, Addicted to music said:

Do not touch the volume control Swap the left/right Input to the amp and play the same track and measure again

Thanks. Yes I tested in same way as you said. Same track played twice . Measured using the decibel meter app at same distance from speaker. As I am not using the proper device but the difference is close to 9db in the max.

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2 hours ago, mbz said:

10dB will be audiable, you can hear the difference but wanted to quantify??? Check your test procedure as above. What model RA-xxx amp? Does it have PRE-OUT/MAIN-IN RCA connectors at rear, if so plug your phone (at minimum volume) into the MAIN-IN's and check for balance. Alst test the preamp by crossing the PRE-OUTs to MAIN-IN with RCA cables, ie, Left PRE-OUT to Right MAIN-IN, Right PRE-OUT to Left MAIN-IN, still same channel louder etc...

 

Most probably a dirty switch or contact issue. Apply gentle pressure to each switch in turn, rock slightly back and forward, then fully switch, any impact? Could also be dirty protection relay...

Yes , one speaker sound is high, I swapped the connection and the same channel is always louder. RA971 Mkll Rotel amp.  Will check the switch tomm. Thanks

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Posted (edited)
1 hour ago, SBM said:

I swapped the connection and the same channel is always louder.

If. by this, you mean you crossed the Left PRE-OUT to Right MAIN-IN etc... then it's a power amp issue or dirty protection relay, not dirty preamp amp switches. Will try and track down the service manual... You could try and give the relay a tap with something non-conductive (chopstick...) while play music, any significant change...

 

EDIT:

Service manaul does not show any PRE-OUT/MAIN-IN RCA's at rear. Also, the unit does not have a speaker protection relay. However there is a relay between the pre/power stages that grounds the audio presumeably during the power on/mute period.

 

So it could be a switch issue. Work through switches as previously mentioned.

Edited by mbz
Update

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1 hour ago, SBM said:

Yes , one speaker sound is high, I swapped the connection and the same channel is always louder. RA971 Mkll Rotel amp.  Will check the switch tomm. Thanks

Thanks, it's faulty switch . Tone switch was not proper.

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Needs a clean then, unless It's badly worn, though It's usually just dirty.

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Can you set different left and right volumes as well? My RC-971 has the split volume knob so maybe that's not quite right. Otherwise the tone controls on it have also gotten a bit iffy but I lose an entire channel with it turned on rather than a difference in volume.

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