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Jul 29, 2026 | 0 comments

How to Choose the Right Vacuum Tube Amplifier Output Tran...

PUBLISHED BY IWISTAO · TUBE AUDIO ENGINEERING Selecting an output transformer (OPT) is one of the most consequential decisions in a vacuum-tube power amplifier. The OPT reflects the loudspeaker load...

Sep 19, 2025 | 0 comments

The Ultimate Upgrade? Exploring Amorphous C-Core Output T...

A 300B tube in a classic SE Class A circuit constantly draws a significant amount of DC current through the primary winding of the output transformer (typically around 60mA). This DC current can easily saturate a standard transformer core, causing massive distortion and a collapse of inductance. To prevent this, SE output transformers must have a small air gap in their magnetic path.

This is where amorphous C-cores shine. They possess a high saturation flux density, meaning they can handle a strong magnetic field before saturating. This property, combined with their low loss, allows designers to create a gapped transformer that maintains high inductance even with the DC bias, a key factor for achieving deep and authoritative bass.