How do I tighten them Just standard B9a,....May be with the tip of a pointed tweezer?
Are grid stoppers supposed to be right next to the valve pin?.........yes, this is for stopping oscillation, if any.
It is metal film too.....Ideally it should be CC type. MF may work if non-inductive.
Regards
Are grid stoppers supposed to be right next to the valve pin?.........yes, this is for stopping oscillation, if any.
It is metal film too.....Ideally it should be CC type. MF may work if non-inductive.
Regards
Ok I took the gridstoppers out and put them right on the socket. I have been playing the amp for half an hour and its dead silent. No noise or hum at all. This is a very sweet sounding amplifier.very detailed I really like it. Hopefully the noise stays away now. It is noisey on switch on and I wondered about inrush thermistors whether it is worth fitting one if so what size. Also I wondered if there is any way to delay the B+ so that the valves are heated up before the B+ comes in.
Thanks all.
What noise when you turn the amp on?
No tubes are conducting, no current in the output transformer.
Are the power transformer, choke, or electrolytic caps making noise during the inrush current to charge the filter caps.
Is the B+ using a tube rectifier, or solid state rectifiers.
If you delay the B+ until the tube filaments are warm, you will get a transient noise when you switch on the B+.
My amplifiers use solid state B+ rectifiers, and there is no noise when I switch on the power.
Some amplifiers have hum when the power is switched on (before the output tubes are warmed up, and the output tube plate resistance goes low, and before negative feedback takes over, the power transformer magnetic field, or the B+ filter choke magnetic field transfers the hum magnetic field to the output transformer.
When the output tube warms up, the plate resistance goes down, and the negative feedback work together to reduce the hum to the low level it is during normal operation.
No tubes are conducting, no current in the output transformer.
Are the power transformer, choke, or electrolytic caps making noise during the inrush current to charge the filter caps.
Is the B+ using a tube rectifier, or solid state rectifiers.
If you delay the B+ until the tube filaments are warm, you will get a transient noise when you switch on the B+.
My amplifiers use solid state B+ rectifiers, and there is no noise when I switch on the power.
Some amplifiers have hum when the power is switched on (before the output tubes are warmed up, and the output tube plate resistance goes low, and before negative feedback takes over, the power transformer magnetic field, or the B+ filter choke magnetic field transfers the hum magnetic field to the output transformer.
When the output tube warms up, the plate resistance goes down, and the negative feedback work together to reduce the hum to the low level it is during normal operation.
Now I have finished the amp. I am able to use it more freely. I think the issue was distortion rather than noise. Caused by having signal playing into the inputs before I switched on. I can confirm that the amp is infact also quiet at switch on and after 15 or 20 seconds all distortion etc is gone as the tubes warm up.
Thanks to all for help and replies with this build. Appreciated.
Matt
