Tube crossover board circuit based on Marantz model 3 + daughter boards

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This is the bare PCB of a tube crossover board , circuit based on legendary Marantz model 3.

The circuit is a 6dB/oct 2-way crossover design, using three 12AX7 ( or three 12AY7, or 1 12AU7 and 2 12AX7). 6dB/oct gives a most natural roll off and musical performance on listening.  Original Marantz users manual recommended users to use different frequencies for the high pass and low pass section to suit various speaker design. This is a prophetic idea at the time when electronic crossover was just emerging. Nowadays crossovers used to set high and low to have the same frequency but this is not necessarily the best sound to our ears.

In this incarnation,  we use daughter cards to change the crossover frequencies, instead of rotary switch, as rotary switch extended to the front panel can deter the sound by the switch contacts and long signal wires from switch to the board.


We follow the original design to include light bulb circuit so users can build their chassis with the bulb included as the power indicator.

This listing includes one main board, three pairs of daughter boards, two daughter boards sockets and a light bulb.

For users wanting more daughter boards, there is another listing to order them.

We provide schematic, part list and a frequency table for the capacitors on the daughter boards.

Each board contains one audio channel that branches into the high pass and low pass output. For stereo application, two boards are needed.


PCB dimension : 147mm x 228mm.



PCB thickness : 1.6mm
Copper thickness : 70um( 4 times standard copper thickness !)

Supply voltages : 1. DC 250V - 280V DC 20mA , 2 DC 28V 500mA





We do air shipping worldwide at US$7.00. We welcome combine shipping.