Need help with Yamaha HS8 - modding and fixing hiss issue

[FrenDave]

Hello,

from one day to the other the left speaker of my ~10y old Yamaha HS8 started to make a very annoying hiss sound. It really starts to hurt in my left ear after sitting in my homestudio for a longer time.
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I am pretty sure there is something to replace at the amp. The hiss sound is also noticable when no XLR cable is connected -> power cord only. I have already changed cables, used another socket-outlet etc. my right speaker works fine but the left always has this annjoying and hurting hiss sound.
I have experience in soldering (did some condenser mic mods already) so my goal is not only to fix this issue but also to mod the hell out of my hs8.


On this video the NJM4558M are replaced with OPA1602AIDR - I haven't found any info on the internet about this replacement - only some russian forum...

So my questions are:
What parts should I check to fix the hiss-issue and what are the best parts u can buy to mod my hs8 to as neutral sounding for mixing/mastering? (max. price for parts 300€ / 300$). Is there some info how zenmod is done?

Thanks in advance!

 

[user 130681]

It could be an NJM4558 that is noisy. I would disconnect the output section from the power section to check where it comes from.
It may be the output chip at fault, removing R359 (18 Ohm SMD resistor) will separate the pre from power amps.
I wouldn't change SMD components unless you are skilled in hot air or IR desoldering.