GerusAudio 300B Build Process, Updated 06/11/18


Both the 300B amps from my first batch are sold!

The 6A3 is still for available. See my "Amplifiers For Sale" page.


I'm currently building a batch of four 300B amplifiers. The first 2 should be complete by 07/15/18

General Specifications

Tubes Included: 2-6SH7's, 1-GZ34

Rectifier: GZ34

Input/Driver: 6SH7

Power: 8 Watts per channel before clipping (About 9 watts with some clipping)

Output: 8R

OPT’s: Lundahl LL1664 60mA

Frequency Response: 9Hz - 57KHz -3dB measured at 1 watt

Input Sensitivity: 1.8 Vrms for 8 Watts into 8 Ohms

Hum: none

Size: 16W, 13D, 7.75H

Weight: 35 lbs.

Power Supply: 425VDC at 140mA

Valve operating voltages:

6SH7: 225V, -4V, 10mA (Triode Mode)

300B: 350V, -74V, 60mA

Coupling Caps: Jensen Copper Foil in Oil, .22uf


Shipping to lower 48 states only


Before I list the amplifiers for sale, I listen to the each one for 10-20 hours, re-check the voltages, power output and frequency response.


Some basic Wood Work!

This batch is Walnut

Cut the Radius

Route the chamfer

Transformer side covers

Chamfer the side covers

Finished top plates

Cutting, Drilling and Bending Steel

Bottom Covers

18 gage mild steel, painted with Hammered Gray

Transformer Covers

18 gage mild steel, painted with Hammered Copper

2/19/18 Update

Varnish Sides

Varnish Top Plates

Rough Idea of Parts layout

The Input/Driver Power Supply Board

The Back Plate

3/05/18 Update

The Power Transformer

The main power transformer is rated at 600mA. The amplifier draws about 250mA. So no need to worry about this bad boy being over loaded!

The input/driver power supply

This is board supplies the DC voltage for the input/driver. Zener diodes are used for the "G2" voltage.

The "Ultra Path" Capacitors

The 300B's use the "Ultra Path" configuration.

Close up of the Rectifier

This is the "Hybrid Rectifier"