squidman
Member
I bought 251 from NOS Audio and am studying how to make it.
When I use this microphone, there is a hum noise, so I replaced all the parts of the microphone, but the hum still occurs. (See the picture above.)
So I replaced all the parts of the power supply, but the hum noise still persists.
In some parts, there was a very loud wind noise, white noise, and other noises.
So I ended up buying a similar type of power supply (120V, 6.3V output)
and the microphone is producing very good sound.
The design of the power supply is as shown in the picture below.
As a result, I can use the mic now without any problems,
but as a learner, I would like to solve the power supply problem now.
What is very shocking now is that when I buy another tube mic and connect it to the current power supply, it works very normally.
I am really confused.
A mic + A PSU = hum (NOS 251 kit)
A mic + B PSU = works fine
B mic + A PSU = works fine
B mic + B PSU = works fine
Why on earth does this happen?
I tried replacing the ground and transformer by type, but it was still the same.
