auto bias system

This section dives into the technical concept behind the Single 25’s proprietary autobias system, which combines the tonal clarity of "grid bias" with the adaptability of "cathode bias". Below, I’ll explain why this unique approach makes the Single 25 stand out.

First, the Single 25 doesn't rely on a traditional "cathode bias" system. While cathode bias circuits have the advantage of self-regulating properties—automatically adjusting as tubes age or vary—they often lack the sonic authority I strive for. They are known for producing a warm, rounded sound, but can sometimes feel mushy and lack the tight, articulate presence that some musicians desire.

In contrast, the "grid bias" method, also known as "fixed bias," gives the sound a strong grip and definition, providing clarity and punch. The downside is that it requires periodic manual adjustment since tubes tend to drift over time, necessitating bias checks and resets to maintain optimal performance.

The Single 25 employs the grid bias approach to retain that tight, authoritative sound. However, it incorporates an analog proprietary circuit that continuously monitors the current flowing through the tube. This way, you get the sonic benefits of grid bias—speed, precision, and authority—while enjoying the self-regulating ease typically associated with cathode bias systems.

And don't worry about missing the warmth typically associated with cathode bias—since the Single 25 is single-ended Class A amplifier, it delivers rich, warm tones naturally, ensuring you get the best of both worlds.