Converting Solid State to Tube Rectification on a Preamp

@salectric

A solid state power supply often uses a full-wave-bridge (4 diodes) that can be fed by a power supply winding that does not have a center-tap.

Is it possible to use two 6X5 or one 6X5 with 2 Schottky Diodes, and add a heater transformer to make use of the existing power transformer?

How about using four rectifier tubes like 6AX4 to create a full-wave bridge?

@zipost
Do you have the schematics of your Blue Circle 21 preamp? and what is the B+ voltage?
BTW, I also found a BC21.1 with outboard power supply on usaudiomart.
http://www.usaudiomart.com/details/649027319-blue_circle_211_tube_preamp_with_bcg31_power_supply_fre...

...so you need to check all 4 tubes in tube rectifier bridge if operational?

So, it can be done, the question is why you want to do that!

Oops!
one more thing, as mentioned by salectric: the resulting B+ voltage will be lower than with a solid state rectifier, that may or may not be a problem.

why would i change a solid state rect. to tube??? I am curious to see if a tube rect will outperform a solid states in my preamp.

Using four rectifier tubes like 6AX4 to create a full-wave bridge and a 6V 5A power supply for heaters should work, This is a schematic for your referance:

http://1.bp.blogspot.com/_ZXzBbxBRjUc/TVKRXcVOklI/AAAAAAAAAGc/i_zXDoVqTHw/s1600/6CB5A-PSU-Graetz-6AX...

maybe add some high DC voltage rating spdt relays control by a switch so you can select between tube or solid states rectifier.

if i decided to do just a half wave rectifier using a single tube 6x5, is that possible?   Also, with the secondary measure at 350v, that is more than enough for a single 6x5 plate voltage?

Sorry I don't have an answer for your question, but if you really want to use a single 6X5 with the existing transformer, check out this link:
http://www.antiqueradios.com/forums/viewtopic.php?f=13&t=176225