[Suhrm]

Hi
 
i have recently build an a47 amp using this layout http://www.head-fi.org/t/531454/lightbox/post/7173951/id/85920 , and i am now experiencing a hum sound from my headphones when a source signal is not being transmitted, and when a source signal is being transmitted the hum disappears.
the to power the amp im using a 9v battery
the build i in a tin case, both jacks are isolated, and non of the components are getting warm.
 
could anybody help removing the hum?
 
Kind regards 
Rasmus Suhr Mogensen

 

[Grumus]

 It sounds like it's a grounding issue. Does the hum stop or decrease if you touch the input and the case at the same time? Make sure you have connected the jacks to ground and that the case is connected to ground at one point. This will make the case a faraday cage shielding the insides. 

Edit: I looked up the thread you refered to and grounding the case does not look like a good idea. Still sounds like a grounding issue to me. Does the hum stop as soon as the source transmitts or does the music drown it?

 

[Suhrm]

thanks . I forgot to connect the case to the ground 

 

[Suhrm]

Quote:

 It sounds like it's a grounding issue. Does the hum stop or decrease if you touch the input and the case at the same time? Make sure you have connected the jacks to ground and that the case is connected to ground at one point. This will make the case a faraday cage shielding the insides. 

Edit: I looked up the thread you refered to and grounding the case does not look like a good idea. Still sounds like a grounding issue to me. Does the hum stop as soon as the source transmitts or does the music drown it?

no it does not mute it, it "stops". 
 
phew, good thing i have not done anything yet

 

[Grumus]

Looking at the thread again it seems you have to ground the input ground to the case http://www.head-fi.org/t/531454/mullet-a47-thread/15#post_7175688
 
I would suggest reading through the entire thread and try grounding the input to the case (NOT the output jack). You could solder a wire to the ground of the input and touching the case with the other end when the device is on. If this helps then ground it with solder and check to see if anything is getting hotter than usual.

 

[Suhrm]

Im am also experiencing a loud click when turning the amp on and off, could the power caps be bad, if so how do i measure without a capacitance meter. (i have an oscilloscope, but i am still learning how to measure different components).
 
Thanks in advance 
Rasmus Suhr