Tube PSU Question

[Tony]

here's mine i designed for frank's ultimate tube preamp:

[Jay]

Miles Prower, thanks for the explanation. Now I know why my tube amps used small caps I was thinking about my pre-amp supply I think 100uF is not big for a pre-amp is it? Hmmm... so where would the amp source the current for bass slam?

[Sherman]

Originally posted by Jay
Miles Prower, thanks for the explanation. Now I know why my tube amps used small caps I was thinking about my pre-amp supply I think 100uF is not big for a pre-amp is it? Hmmm... so where would the amp source the current for bass slam?

Use a small cap for the first cap after the rectifier tube. Then use progressively larger caps through the filter section.

Using a 5U4-G with a max cap value of 40uF I built a filter section using 5U4-G -> 40uF -> choke -> 55uF -> resistor -> 80uF. The VT rectifier seems perfectly happy with this arrangement and there is sufficient current reserve.

[philipbarrett]

Thanks all, this is great stuff. I think PSU design looks simple but is anything but.

What value would you recommend for the 1st cap? Is there an altogether better way of filtering here?

One more question on PSUD2; is CT transformer voltage rated to center or between the outputs (250-0-250 would be a 250V or 500V)?

Thanks again.

PB

[Sherman]

Originally posted by philipbarrett
Thanks all, this is great stuff. I think PSU design looks simple but is anything but.

What value would you recommend for the 1st cap? Is there an altogether better way of filtering here?

One more question on PSUD2; is CT transformer voltage rated to center or between the outputs (250-0-250 would be a 250V or 500V)?

Thanks again.

PB

According to the data sheet the max cap value for a cap input filter is 50uF.

In PSUDII the voltage is from secondary to CT, that is if your trafo is rated at 250-0-250 then use a value of 250 in PSUD.

[opik]

Originally posted by Miles Prower
Here's something else that will come in handy for this: Rectifier Applications Handbook

thanks a lot!

regards, opik

[Tony]

I think 100uF is not big for a pre-amp is it?

frank"s ultimate tube amps uses big caps:

12bh7a_srpp


350volt psu


i made a psu using ss parts shown in my post above. it is a voltage doubler using mr4100 rectifers, large caps, and transistor series pass element.

[Joel]

Yes, but it also has a 1A power transformer, and a solid state bridge rectifier.

[Tony]

Originally posted by Joel
Yes, but it also has a 1A power transformer, and a solid state bridge rectifier.

fedgrove must have felt that big transformers and ss bridge provides for better regulation! very desireable for srpp amps.

costs aside, makes a lot of sense to me.