Choosing a power transformer for a tube amp or preamp is one of the most consequential decisions in a build. If you're looking at transformers voltage regulation, the Antek AS-1T250 is a 100VA toroidal option that bundles dual 250V secondaries with dual 6.3V heater windings. It's priced at USD 56.00. This review covers how those specs match your project.
Quick verdict
For a medium-power tube amp or preamp, the AS-1T250 is a straightforward choice. It brings flexible high-voltage and heater secondary windings, shielding against noise, and a price of USD 56.00. The 100VA capacity is the ceiling; it isn't designed for high-wattage output stages.
Who it suits
This transformer fits builders working on preamplifiers and medium-power amplifiers that need 250V plate voltage and 6.3V tube heaters. The two 250V windings can be paralleled for more current or series-wired for a center-tapped supply, while the two 6.3V windings can feed separate heater strings or be combined. That makes it a strong candidate for a range of tube circuits.
Antek AS-1T250 Tube Amp Power Transformer
This 100VA toroidal transformer provides two 250V output coils and two 6.3V/3A heater coils, with independent leads for each winding. The independent outputs are designed to be connected in parallel for more current or in series for double voltage with a center tap. A reason to choose it is the static shield between primary and secondary; it improves isolation and reduces noise interference, provided you ground it. The main limitation is the 100VA rating, so it's best matched to circuits that stay within that power draw.
What stands out from the listed details
The static shield and external magnetic shield are the features that matter most for audio use. The magnetic shield is meant to reduce magnetic leakage, and the static shield blocks some power-line noise from coupling into the secondary circuits. The dielectric strength is rated above 3500V between primary and secondary, which speaks to safety in a high-voltage tube amp environment. The heavier-gauge wiring is intended to avoid copper loss during full power output, so the transformer is built to hold up under sustained load.
Meaningful trade-offs
The 100VA capacity is the most important trade-off. This transformer is made for medium-power amps or preamps, not for a high-current output stage that draws more than that. The static shield only works when properly grounded, so wiring mistakes can undo its noise-isolation benefit. And because each winding is independent, you'll need to plan your parallel or series connections carefully to get the exact voltage and current configuration your circuit requires.
Bottom line
The Antek AS-1T250 is a capable 100VA toroidal transformer for medium-power tube amp and preamp builds. Dual 250V and dual 6.3V windings give you flexibility, and the shielding features are genuinely useful for keeping hum and noise out. At USD 56.00, it's a practical option for the listed features. If your power draw stays within 100VA, this is a transformer worth serious consideration.
