Vishay HEXFRED Full Bridge Rectifier
A direct-replacement audio power-supply upgrade using four individually selected ultrafast, ultrasoft-recovery diodes.
Why Build a Discrete Bridge When Standard Bridges Are Everywhere?
Because the rectifier is inexpensive, but it is not sonically insignificant.
In an audio power supply, the bridge rectifier repeatedly switches the transformer secondary into a reservoir-capacitor load. That charging action occurs in short, high-current pulses. The reverse-recovery behavior of the diodes, together with transformer leakage inductance, wiring and PCB layout, can generate narrow current spikes and high-frequency ringing.
A carefully chosen soft-recovery diode does not magically create musical information. Its practical purpose is to make diode commutation more controlled and to reduce one possible source of high-frequency disturbance in the power supply.
Listening impressions are subjective and the result will depend on the complete circuit, transformer, grounding, reservoir capacitance, snubbing and system resolution.
Built with Vishay HEXFRED Diodes
Each module uses four genuine Vishay VS-HFA08SD60S-M3 diodes. This device is a HEXFRED ultrafast, ultrasoft-recovery silicon diode selected for low recovery charge, low peak recovery current and reduced EMI/RFI in demanding switching applications.
It has also earned an excellent reputation among experienced audio builders for combining speed and clarity with a natural, musically convincing presentation. That balance is why VALAB selected it for the power supply of a new amplifier project—and why we decided to make the same part available to other DIY builders.
Small Investment, Meaningful Upgrade
- Four discrete Vishay HEXFRED soft-recovery diodes
- Common four-terminal bridge layout: DC+ / AC~ / AC~ / DC−
- Pure copper terminal pins for robust, low-resistance connection
- Compact physical format intended to replace many standard flat bridge modules
- No external heatsink required in VALAB's intended low-to-moderate-power application range
- Suitable for amplifier power supplies, DACs, CD players, preamplifiers and other audio DIY projects when voltage and current requirements are compatible
This is the kind of upgrade that requires little money and only a small amount of work, yet it addresses a component through which every charging pulse of the power supply must pass.
Technical Specifications
| Module topology | Full-wave bridge rectifier, four discrete diodes |
|---|---|
| Diode manufacturer / model | Vishay VS-HFA08SD60S-M3 |
| Diode technology | HEXFRED ultrafast, ultrasoft-recovery silicon diode |
| Repetitive reverse-voltage rating | 600 V per diode (manufacturer component rating) |
| Continuous forward-current rating | 8 A per diode at TC = 100 °C (manufacturer rating under specified case-temperature conditions; not the assembled PCB's continuous-current rating) |
| Single-pulse forward current | 60 A per diode (manufacturer component rating under specified conditions) |
| Reverse-recovery time | 18 ns typical at IF = 1 A, dIF/dt = 200 A/µs, VR = 30 V, TJ = 25 °C |
| Forward voltage | 1.4 V typical at IF = 8 A, TJ = 25 °C |
| Terminal order | DC+ / AC~ / AC~ / DC−, as marked on the PCB |
| Terminal material | Pure copper pins |
| VALAB application recommendation | Audio equipment below approximately 200 W, subject to the actual transformer secondary current, capacitor charging current, ambient temperature and installation conditions |
| Package contents | 1 × fully assembled VALAB full bridge rectifier module |
Headline diode ratings come from the Vishay component datasheet. The finished bridge module is limited by the PCB copper, terminal pins, solder joints, airflow and installation—not only by the rating of one semiconductor.
Designed as an Easy Replacement
The board, terminal spacing and overall layout were designed around the familiar flat four-pin bridge-rectifier format. For compatible equipment, replacement is straightforward.
- Unplug the equipment and fully discharge all power-supply capacitors.
- Confirm the original bridge's four-pin spacing, available clearance and exact polarity order.
- Install the VALAB module according to the PCB markings: DC+, AC~, AC~, DC−.
- Recheck every connection with a meter before applying power.
Power and Thermal Guidance
During development, a prototype module was operated in a VALAB amplifier test environment of approximately 300 W without noticeable temperature rise at the rectifier. This demonstrates useful efficiency in that particular circuit; it is not a universal 300 W module rating.
Amplifier wattage alone does not determine bridge stress. Transformer voltage and current, reservoir-capacitor value, conduction angle, turn-on surge, chassis temperature and airflow can make two “200 W” amplifiers place very different demands on a rectifier.
For high-current supplies, very large capacitor banks, severe surge conditions, motor drives, inverters or industrial power conversion, please use a bridge and PCB specifically engineered for those loads. If this module becomes significantly hot in operation, disconnect power and select a higher-capacity solution.
Where It Makes Sense
- Replacing an ordinary molded bridge rectifier in a compatible audio power supply
- New amplifier, preamplifier, DAC and CD-player DIY projects
- Builders seeking lower-recovery-noise rectification without designing a discrete bridge PCB
- Systems where fine detail, transient articulation and power-supply refinement are worthwhile goals
It may be one of the least expensive parts in the power supply, but it is certainly not the least important. The rectifier is a small component with a direct role in every reservoir-capacitor charging event.
Please Read Before Purchase
- This product is intended for experienced audio DIY builders and qualified technicians.
- High-voltage power supplies can retain lethal energy after power is removed.
- Verify voltage, current, polarity, pin spacing, clearance and thermal conditions in your own circuit.
- Do not exceed the ratings of the diode, PCB, wiring, transformer or other power-supply components.
- Sound descriptions are VALAB's subjective listening observations, not guaranteed results in every system.