One channel louder than other

loudel · 31st July 2010, 04:41 AM

My Music Angel running 4KT88 in p/p has one side (channel) louder than the other. A little more info- the system has been running on and off for several months then one channel died. Took it to my Chinese 2nd hand audio repairer who replaced 4 (2x2) 3w resistors with 5w. Sound is back but noticebly less on the repaired channel. Have change the speakers/cables and outputs to no avail. I'm not very savvy about the inner workings but not afraid to change caps if need be (after draining them).Huffing it the repairer is a real chore as the unit weighs some 25k and I have to cart the thing in a suitcase on a plane.
Any suggestions?

TheGimp · 31st July 2010, 05:10 AM

1st I'd try switching tubes between channels, If you don't find any differences then start taking measurements.

I would recommend ohm-ing out all resistors and comparing the good to the low channel.

If no differences are found, then I'd measure the Output transformers and look for shorts. The problem is that the DC Resistance may be off considerably between channels. You will have to use a signal generator to verify winding ratios.

tinitus · 31st July 2010, 05:19 AM

maybe check your attenuator

bias ?

voltage ?

loudel · 31st July 2010, 05:51 AM

Thanks, fellas, I had posted a similar query as I thought this 1st post did not get through. Will check and get back but it'll take me a bit of time.The guts of the Music Angel seem quite over-engineered compared to other (usually older) valve amps. Should the fault not be dtectable then I have a good mind to replace everything except the transformers and valves with simpler circuitry - there are several schematics floating around.
Regards
Lou

loudel · 31st July 2010, 10:58 AM

Just an adjunct: have rolled the KT88s but same channel playing up. Then rolled the 12au/ats and seem to notice a small improvement in sound from affected channel.Could be onto something here - I have a couple of spare 12au/at and will roll them later this weekend.Fun.
Cheers and thanks.

31st July 2010, 04:41 AM	#1
loudel diyAudio Member Join Date: Jul 2010	One channel louder than other My Music Angel running 4KT88 in p/p has one side (channel) louder than the other. A little more info- the system has been running on and off for several months then one channel died. Took it to my Chinese 2nd hand audio repairer who replaced 4 (2x2) 3w resistors with 5w. Sound is back but noticebly less on the repaired channel. Have change the speakers/cables and outputs to no avail. I'm not very savvy about the inner workings but not afraid to change caps if need be (after draining them).Huffing it the repairer is a real chore as the unit weighs some 25k and I have to cart the thing in a suitcase on a plane. Any suggestions?

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31st July 2010, 05:10 AM	#2
TheGimp diyAudio Member Join Date: Aug 2009 Location: Johnson City, TN	1st I'd try switching tubes between channels, If you don't find any differences then start taking measurements. I would recommend ohm-ing out all resistors and comparing the good to the low channel. If no differences are found, then I'd measure the Output transformers and look for shorts. The problem is that the DC Resistance may be off considerably between channels. You will have to use a signal generator to verify winding ratios.

31st July 2010, 05:19 AM	#3
tinitus diyAudio Moderator Join Date: Nov 2005	maybe check your attenuator bias ? voltage ?

31st July 2010, 05:51 AM	#4
loudel diyAudio Member Join Date: Jul 2010	Thanks, fellas, I had posted a similar query as I thought this 1st post did not get through. Will check and get back but it'll take me a bit of time.The guts of the Music Angel seem quite over-engineered compared to other (usually older) valve amps. Should the fault not be dtectable then I have a good mind to replace everything except the transformers and valves with simpler circuitry - there are several schematics floating around. Regards Lou

31st July 2010, 10:58 AM	#5
loudel diyAudio Member Join Date: Jul 2010	Just an adjunct: have rolled the KT88s but same channel playing up. Then rolled the 12au/ats and seem to notice a small improvement in sound from affected channel.Could be onto something here - I have a couple of spare 12au/at and will roll them later this weekend.Fun. Cheers and thanks.

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