cary cad211m hum noise

High impedance (tube) amps with nothing connected to their inputs act as antennas and will most likely hum.

Do they hum if you connect them to a preamp and mute the preamp's output ? If not, suspect the preamp connections/tubes.

I suggest that you take a good look at your cable layout. ICs, power cords and speaker cables should always cross at 90 degrees, if possible well away from each other. Paralell cable runs tend to generate hum.

Also, high input impedance tube amps do not like unshielded ICs or carbon-based ICs.
I hopoe this helps

Hi casouza,

Either i any input or not they still have the same level of noise,the noise level is not too high, only i heard it if put my ear close to the speaker specialy the midbass and mid drive, someone toll me that is not hum noise, it is the distortion noise, and all the class A tube amp have this kinda noise?? is that true? these cad211 are my first tube amp, so i don't any experience with tube amp. thank you for your help!

If the noise is only present with your ear close to the speaker I wouldn't worry too much about it. On the other hand if you can hear it fro a few feet away there may be some underlying issues present.