Speaker hiss question (KEF 104.2 and m4.0t amp)

[Guest tonionc]

Hello,

 

I have recently purchased a C-1 preamp and m4.0t amp from the original owner. I was very happy with this system for the first 2 months. I used it with both my KEF 104.2 and DQ 10s. Both sounded wonderful. Over the last month without any making any changes to the system, speaker hiss has increased a lot in the KEF 104.2 speakers, and only minimally noticeable in the DQ10s. I tried to isolate every component, and it seems to be the m4.0t amp that is louder now. I hooked up an older cheap Sherwood amp with the system and the speaker hiss went away (of course it did not sound anywhere near as good as with the Carver system) but this leads me to wonder if the m4.0t amp is causing the speaker hiss or something else? Could it be the speakers? Is this something that is common? Something that could be repaired?

 

I really love the KEF 104.2 speakers. They sound so pure, powerful, great detail. But now they only sound good with the music at a high volume. Playing acoustic bass or guitar, or just vocals, I can hear the speaker hiss so much it is driving me crazy. Does anyone have any suggestions about what might be going on and how I would go about fixing this situation?

 

THank you so much. I really look forward to your suggestions. I realize the situation might be much more complicated but I am hoping to learn from the experts on this forum.

 

Antonio

[RichP714 3,163]

A place to start would be the service manual (you can get it here; the TFM-45 manual is better resolution and also covers the M-4.0t). Look in the troubleshooting section, fault 9, excessive noise or hiss.......

[treitz3 53]

Did you change the location of any of the power cords, IC's or anything else such as your speaker cables when you changed components? Any added appliances, lights or dimmer switches on that circuit?