Poor Man's Tube Mixer

If you just want a few rugged, quiet tube mic pres in a box then the Lunch Box is for you. But it is not a mixer. As soon as you need faders and mixing capabilities you need the Poor Man's Tube Mixer (PMTM). In construction, the PMTM is basically a 3U lunch box minus the rack mounting ears, with an added fader front section. But that is where the similarities end. The PMTM is intended as much as a DIY project as a finished product. As such, keeping materials costs to a minimum is a primary objective. To this end, a number of design simplifications are available:

  • Use a single EZTubeMixer twin line amp PCB to provide two mic pres

  • Replace stepped gain switches with potentiometers

  • Replace expensive input and output transformers with more economical alternatives

  • Replace expensive extruded aluminium module enclosures with the much more economic Mark 3 mixer mechanical design

  • Use a single bus amp to mix both balanced and unbalanced signals

All the above techniques help to significantly reduce the cost of the PMTM.

The base level product shown here provides:

  • two mic pres with phase, phantom, 20dB pad and HPF switches, a gain pot with a range of 26dB to 60dB, a pan pot and TDK slider fader and direct outs.

  • Four balanced line inputs with pan pot and slider fader

  • 24 balanced stem inputs (12 routed to R bus and 12 to L)

  • A pair of balanced bus expansion inputs for daisy chaining with other mixers

The master bus has either a pair of slider faders which can be mechanically linked or a single stereo fader. A monitor output with level control is also provided along with a trim control for the stems. The direct and master outputs are impedance balanced.

Optional extras include output transformers, replacing line inputs with mic inputs and metering.