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.
This article explores the design of a classic SE amplifier, pairing two legendary tubes: the 6SL7 high-mu twin triode as the driver and the iconic EL34 power pentode for the output stage. This combination promises a journey into the heart of vintage audio, delivering a sound that is both powerful and nuanced.
This article provides a comprehensive, step-by-step guide for the advanced DIY audio enthusiast on the intricate process of designing, calculating, and constructing a power transformer from scratch. We will embark on a journey from theoretical principles to hands-on craftsmanship, culminating in a custom-built transformer tailored for a classic stereo EL34B push-pull amplifier. This is not a project for the faint of heart, but for those willing to invest the time and diligence, the rewards are immeasurable.
Learn how the 4-over-3 winding method improves tube amplifier output transformers with higher efficiency, lower distortion, and superior sound fidelity—perfect for Hi-Fi systems and guitar amps.
The primary of tube amplifier output transformer generally has two, three and five connection terminals.
The circuits of single tube type class A amplifier Among them include:
