Since “Xin Zhi Zhao” is not a mass-produced commercial IC, this content assumes you are working on an open-source or custom hardware project (e.g., an optical awareness sensor, a signal reflection mapper, or a core “awareness” circuit). The focus is on the practical updates to the schematic.
Original Xin Zhi Zhao schematics used 0.22µF/630V coupling caps between driver and output stages. The updated version recalculates the low-frequency cutoff based on the output tube’s grid-leak resistor:
Formula used in the update:
C = 1 / (2π * f_c * R_grid)
With f_c lowered from 10Hz to 3Hz, the new value becomes 0.47µF to 1.0µF. This minimizes phase shift at low frequencies, tightening bass response without increasing blocking distortion. xin zhi zhao schematic updated
Before diving into the updated schematic, we must understand the original design philosophy.
The Xin Zhi Zhao is a single-ended Class A amplifier typically utilizing the 300B vacuum tube. It earned its nickname, "The Little Chinese 300B," not because of its size, but because of its ability to produce "western" 300B sound quality at a fraction of the cost.
Original Topology (Pre-2020):
The Problem: The original schematic had a fatal flaw—high output impedance from the cathode follower led to poor low-frequency control (muddy bass) when paired with modern, less-efficient speakers.
A choke rated for less than 150mA will saturate on 300B amplifiers. Select at least 200mA DC rating with 100Ω DCR or less.
In the niche world of high-fidelity vacuum tube amplification, few names command as much quiet respect among DIY enthusiasts as Xin Zhi Zhao (often abbreviated XZZ). Known for blending vintage warmth with modern engineering rigor, Zhao’s designs—particularly his push-pull and single-ended triode (SET) schematics—have become blueprints for thousands of home-built amplifiers. Since “Xin Zhi Zhao” is not a mass-produced
But as with all classic circuits, time reveals opportunities for improvement. Power supply filtering, ground loop suppression, and thermal management are areas where the original 2000s-era schematics have begun to show their age. Enter the "Xin Zhi Zhao schematic updated" —a set of modern revisions that has been circulating through DIY audio forums, GitHub repositories, and PCB design communities over the last 18 months.
This article provides a comprehensive breakdown of the updated schematic, including specific component changes, safety enhancements, and measurable performance gains. Whether you are rebuilding a classic XZZ 300B or designing a new PCB from scratch, this guide will help you understand why the update matters and how to apply it.
The original had a simple bus ground, which created shared return paths. The updated schematic implements a hybrid star-bus ground: [ ] Update BOM with new part numbers and footprints
Result: No more ground loops. Builders report noise floors of less than 0.3mV unweighted.