Tube Filament Supply

Ultra Low Noise DIYHFS current source filament supply. 2.5A, 2.5v-12vdc output (depending on heatsinking)

Output noise ~4mv (typical 300b filament, varies by current draw). Input/Output short circuit protected, overheat protected, output voltage continuously variable with on-board trimmer pot. Through-pcb vent-holes for cooling of critical parts. Can also be mounted flat profile without heatsink by mounting the regulator from the bottom and bolting regulator direct to chassis. Includes mounting standoffs and 4 pcs 0.47r resistors to trim input voltage. Function indicator LED on board. Best quality parts: Nichicon, Schottky etc

Regarding noise measurements (as some have asked): The self noise of the filament supplies is in the uV range but since there is always limited ripple rejection from any filter network, self-noise is swamped by in-circuit factors and is meaningless. The 4mv measurement posted is actual measured output ripple (actually we see 2mv-4mv range) in the amplifier chassis driving a working 300B. If you measure a typical diode bridge you will observe several 100's mv output so this is a very significant noise reduction. Also remember the 2-4mv is not at the transformer output, it is at the filament of the tube and will allow extremely low noise at the speaker outputs if the rest of the amp is implemented properly (we typically see 0.3 to 0.5mv at our amp output which is respectable even for a linestage.)

We are now shipping Rev B which is locked as a VCS and includes one more active device which gives a 60 second ramp up to full output voltage.

Application notes (pdf)


Basically the circuit design and the device chosen allows it to function as a VCS.
By adding/subtracting some parts the pcb (see application note) can also be configured as a pure CS or VS, if desired. As supplied it functions as a VCS.