Unregulated Tube PSU parameters

[Nikon1975]

Dear All,

I am building the tube amplifier proposed here:

KT88 Single Ended (SE) Tube Amplifier

The power supply is very simple, but with this design I could hear some hum, so I decided to increase the filtering, adding a second LC filter, so reaching the following configuration CLCLC with the following values 10uF Solen - 10H -47 uF Film - 5H - 47 uF.

Having two filters maybe is not optimal, as like someone said is like "travelling putting two cars one over the other"

Someone commented that it would change the sonic of the amplifier.

What's the best approach ? I am using PSU2, but I am not sure what to optimize for (minimize ripple , make the psu faster) as for the first I am tempted to increase capacity, for the latter to decrease.

I have some constrains:
1) My transformer has the following specs
Primary 100 V R 1.4 ohm
Secondary 360-0-360 V R 37 ohm off-load voltage 389 V
I added two 50 ohm resistor to the secondary to increase the DCR to comply with the request from the rectifier.
2) For mechanical reason I can have only two 47 uF film capacitors
3) I can accommodate more Solen capacitors, available value 10uF , 22uF 47 uF
4) I have 10 H dcr81 and 5H 93 dcr inductor. If I can avoid the second one is better as the 10H is rated for 300 mA, while the 5H only for 180 mA
5) There is a further option to add more filtering only to the B+ of the drivers. In this case I could use 30 H dcr 125 ohm 30mA.

What do you think is the best configuration ?

Additionally I wanted to bypass the capacitors. Studying a bit I found the following equations to calculate the values:

Rdamp > 2 * SQRT(L/Cdamp)
Rdamp <SQRT(L/Cbyp) /2
Cdamp > 16 Cbyp

This brings me to vales of Rdamp=1K and Cbyp=2.2uF. This would fit almost to any combination between LC that I have. Is it correct ? Does it make sense ?

Thank you for help,

Davide

[Nikon1975]

Not the most popular thread :-( .

Guess my questions are quite dumb ?

D.

[Tony]

hi,

you might want to try to lift the heaters to some dc voltage, say ~20% of b+, that should eliminate most of your hum....