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Help: Yamaha DSP A1 amplifier's right channel not working well

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I'm having some trouble with my Yamaha DSP A1 amplifier. It sounds like the right channel is giving a weak or sub-par performance. It's relatively subtle, but seeing as my wife agrees with me it must be true.


It sounds as if one of the two mid-range speakers might not be operating, like that side is lacking something. 


Also, occasionally after turning the system on there will be zero sound coming from the right. After turning off and on this usually resolves itself.


However, I've recently started using the amp's headphone socket, and have noticed that if I plug and unplug from the headphone socket a few times this can lead to the sound returning to the right channel.


This leads me to believe there is something amiss to do with this part of the amp.


However, even after regaining sound from the right speaker it sounds slightly weaker, lacking in clarity, as if one of the right tower's speakers is not working.


I am an utter novice, so please forgive me.


I've switched cables and attached speakers to the opposite outputs. When attached to opposite outputs the issue follows to the left channel.


Any help would be much appreciated, and if there's anywhere else I should ask this question please let me know.

Edited by Christopher L. Handlebars
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Try changing your input source position and using a different position on the selector switch.  It is common for the selector switch on that error of DSP amps to develop bad connections.  Not 100% sure about the A1 but definitely the later ones.  If you wiggle the selector switch does it crackle?


Although if it follows the speaker it is probably in the speaker.

Edited by Dwizzle
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Agree could be dirty switch contacts, wiggle/try different source position as above. May also be dirty relay contacts. Try to localize the problem as a pre or power amp issue by using the PRE OUT/MAIN IN RCA at rear. Using RCA cables cross the connections, ie, go from LEFT PRE OUT to RIGHT MAIN IN. Also Right pre-out to left main-in. If problem switches to left channel then preamp issue, eg, dirty switches... If problem remains on right channel then power amp and possibly protection relay.

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I've got a Yamaha dsp-a1000 and had the same issue. From what I could gather, the mechanical input switches used by Yamaha back in the day weren't the best. 


I bought some WD-40 contact cleaner from Bunnings and sprayed that in the input selector and gave it some turns to work it in. 


That seems to have fixed my issue, it might be worth looking into for yours as it's sounds like it could be the same thing. 

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Thanks so much for your replies everyone, I'll get my head around what this advice means, implement it, and get back to you!


Also, the problem doesn't follow the speaker, it follows the output to the speaker. I changed cables but the issue remained. And no crackling is evident.


Off-topic , but failing these solutions, any recommendations for older high quality amps I should try to get my hands on?

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So I tried:


1. Changed input source position and position of selector switch. Issue persists.


2. Crossed and recrossed pre-out and main in using RCA cable at rear. Issue persists, moving from left to right speaker depending upon connection configuration.


3. Haven't tried WD-40 yet, but haven't had an crackling or anything due to moving the selector dial.


Apart from dirty switches are there any other likely culprits?


It strikes me as strange that on occasion sound to the right is completely lost, and will return (though in its sub-par form) upon inserting and removing a headphone cable a couple of times.

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The Yamaha DSP A-1 is a decent unit for digital, it's only 20 years old so shouldn't be too many issue. If you go for vintage then you are up for refurbishment, no issue if you diy. All the main players made some tasty gear during the 70's-80's. It comes down to what sort of sound you want and to some extent(for some people) what look. Some of the smaller units punch well above their weight, eg, Sansui AU-505/555/555A, Luxman L-30/31, SQ-505X/507X. Marantz and Pioneer receivers are sought after, however I'd suggest going separates, eg, Yamaha C-70/80, CX-1000, CX-1/M70/80, MX-1000, MX1 also gear from HK(citation series) and Adcom and... I'm still lusting after a Sansui alpha 907__ or even a 707...

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3 minutes ago, Christopher L. Handlebars said:

2. Crossed and recrossed pre-out and main in using RCA cable at rear. Issue persists, moving from left to right speaker depending upon connection configuration.

Confirmation that it's a preamp issue.

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Yamaha CA-1010, CA-2010 would be in that ballpark, Luxman L-410/430 would be cheaper. Will try and look at schematic later re your channel issue.

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The DSP A-1 appears to be well regarded/worth keeping.


At next occurance slightly adjust the balance to the left, note any effect if lost channel or improved sound quality. Repeatadly (un)plugging the headphones will load the upstream circuit, ie, tone amp IC802(uPC4570), the
balance sits behind this.


You should also gently rock/select... the other controls in turn and note effect, eg slightly increase vol, bass, trebble. 


Will need an oscilloscope to track this down. The lost channel should be reasonably easy to find, hopefully the sound quality issue is related otherwise it would be a difficult fix.

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Again, thank you for all your help. I've given everything a gentle twist and rock but to no avail. However, I've found a slightly nicer version for a good price (got wood panels down the sides), so I think I'll pick it up and keep this one as a spare for any transplants I may need in the future. My dad actually found this amp in the throw outs a few years ago, so it's been good value while its lasted! It'll be nice to have a remote and a working display... 

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