This module offers 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. Also, can be mounted flat profile without heatsink by mounting 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.

dimension: 85mm x 50mm x 60mm (tall).
four fixing holes: 40mm x 75mm.
output ripple voltage: typically 4mv into 300B (example)

discussion & installation instructions


Price for 1 pair = £80.00 + VAT + Shipping - same price as from DIY Hi-Fi Supply
 

What is needed?

1. low noise heating current (ie low ripple and no high frequency hash)
2. no intermodulation between signal and heating current
3. no audio signal loss through heating current device

• straight-in AC. Needs hum pot to reduce hum but will still always be audible on efficient speakers. Impractical for >2.5v filaments even with hum pot. Hum pot always in the signal path and acts as shunt for signal. Filament voltage unstable as varies with line voltage and load. Fast startup stresses power tube.
• AC to bridge rectifier to big cap. Most basic DC supply, ripple still in 250-300mv range and needs hum pot. High frequency artifacts from solid state rectification gives nasty glare. Voltage unstable as with straight-in AC. Fast startup stresses power tube
• AC to bridge rectifier to choke to big cap. Low ripple 80mv, suppressed high frequency hash. Voltage unstable as stated in 2. Switch-on a little slower than in 2. Sound is good. Big choke needed and not space friendly.
• AC to bridge rectifier to regulator. Can be voltage stable give low noise of only a few millivolts. Sound depends on implementation, needs AC voltage headroom to regulate (ie DCV out = ACV in +1 to 2v)

• Any voltage fluctuations across the cathode are part of the output circuit (cathode-anode-output transformer). Audio signal produces music at the outputs. Any fluctuation (high/low frequency) in the heating current circuit produces noise at signal output. Such noise can modulate audio signal and create harmonics that colour (distort) the audio signal causing subjective glare, warmth, exaggerated or diminished detail etc.

• Current will always take the path of least resistance. 100% of audio signal should stay within the tube/transformer output circuit. Caps across the filament will short a percentage of audio signal. Any path with resistance lower than the net output circuit loop will reduce audio signal through that loop. Subjectively audio output quality suffers in every way.

• Can be implemented as "current source" CS or "voltage source" VS or "voltage-current source" VCS (ie current source at audio frequency and voltage source at DC)
• VS: voltage source is like a battery: low output impedance and tends to maintain voltage regardless of load, irrespective of current. Good for stabilizing voltage, bad for intermodulation with audio signal as impedance of the device is low
• CS: current source has high output impedance and tends to maintain current regardless of load and irrespective of voltage. Good for preventing intermodulation and loss with audio signal as output impedance is very high. Bad for voltage stability
• VCS: voltage current source. Acts as a current source at audio frequencies but as a voltage source at DC. Benefits include voltage stability, High impedance at audio signal frequency (audio signal sees a 'brick wall' and doesn't go there). No shunting/shorting paths for audio signal, all signal stays within the audio output circuit. No humbucker or caps across cathode used in this implementation - This is what the DIY Supply Filament Module does