Valve Amp Blog

Valve Amp Blog

Sound advice

Build guides, parts lists, valve comparisons and amp know-how from the team at Evatco, Australia's valve amp parts specialists.

The Dumble Overdrive Special: How It Gets That Smooth Gain image


Date Posted: 21 October 2026

No magic parts, just clever design. How Dumble's Overdrive Special shapes, filters and cascades its gain stages for that smooth, singing lead tone. Note: The values discussed here are typical of Dumble ODS #124 and many popular clones (Ceriatone, etc.)

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SoZo Capacitors: What's the Fuss, and Are They Worth It? image


Date Posted: 20 October 2026

Yellow Mustard or Blue Molded? An honest guide to SoZo capacitors, what they really change in your amp, and when our metal film caps do the job just as well.

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Fixed Bias vs Cathode Bias: The Formulas, and Cool, Warm or Hot Settings for Popular Amps image


Date Posted: 20 October 2026

The maths behind biasing: how to work out idle current for fixed-bias amps, how to check a cathode-biased amp, and cool, warm and hot settings for popular amps.

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12AU7 Equivalents image


Date Posted: 2 October 2026

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JJ Electronics 12AX7 / ECC83S Review image


Date Posted: 21 September 2026

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5F1 Champ Parts List image


Date Posted: 16 September 2026

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5E3 Parts List image


Date Posted: 2 September 2026

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5F6A Parts List image


Date Posted: 1 September 2026

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E34L vs EL34: What's the Real Difference? image


Date Posted: 12 August 2026

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Should I Build a 5F1 or 5E3? image


Date Posted: 11 July 2026

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Phase Inverters: Do You Need a Balanced Tube? image


Date Posted: 15 April 2026

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Understanding Rectifier Tubes image


Date Posted: 3 July 2025

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To Bias or Not to Bias image


Date Posted: 3 July 2025

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