How long do you reckon it will take to completion? Can’t wait to hear your thoughts on your views on the sound.
🙂 china amorphous core is good .we are used in 2 coil winding on c-core in f2a project and 300b ...211...gm70....🙂
Tonight I finished connecting the circuit and testing. It works, and sounded very good. The voltage of each tube is correct. But massive humming, begin finding the problem. And one more problem, when my hand getting close to the first stage 310A (but not touching it), the humming getting stronger
Hi jerry. Very well done so far. I have the very same problem with a valve preamp. I have narrowed it down to a loop, causing the hum. If I run the pre through a isolation transformer, gone. Check your grounding, and try shield the tubes. They are microphonic. This helped me out a lot. Regards
use a shielded cable for the 310A top grid (like a coaxial) and put the shield to the chassis and your hum will be gone 🙂
Thank you for the good advice. I have used shielded cable for 310A，and put the shield to the chassis, the hum reduced a little. It seems another things still caused the hum
Hi Bren. I will check each stage to find out what causing the hum. I will post the process and help me with that, thanks.
Began to trace the source of the hum
Arrangement of the circuit for now
Voltage of the hum is about 1.7V(quite high than any other AMP I made)
Arrangement of the circuit for now
Voltage of the hum is about 1.7V(quite high than any other AMP I made)
I followed this sequence of GND
The order of GND on the PCB
Connection of PSU, AMP and chassis
Is there any problem of GND?
The order of GND on the PCB
Connection of PSU, AMP and chassis
Is there any problem of GND?
