French  English  



The MP573 is a two stages, single ended class A preamp, based on the design that was originally used in the Neve 1290/1073 modules, that has been adapted to the '500' format of API.

Just install it in your API* compatible LunchboxTM rack and start recording.

The sound of the MP573, like its model is full, silky, detailed and musical, slightly larger than life, very complimentary to a digital recording environment.

The MP573 is great on vocals, acoustic instruments and generally all close miked sources that need to be pushed forward in the mix.



  • Single ended class A design
  • Carnhill/St. Ives transformers on input and output
  • 0 to 70 dB of gain
  • Switchable first stage
  • The output stage is biased in a rich Class A with 70mA of iddle current
  • Fet DI input, relay switched, the signal passes through the input transformer
  • Signal/Clip LED monitors clipping in both stages
  • 24V supply built from the +/-16V with a linear regulator
  • Golden contacts on relays and switches
  • Jumper selectable input impedance : 300-1200 ohms.
  • High quality Grayhill gain switch
  • Nicely damped quality conductive plastic potentiometer
  • High precision aluminium knobs
  • Tantalum capacitors in the audio path (as in original)
  • High grade 105°C low ESR electrolytic capacitors
  • WIMA film capacitors
  • High grade double sided PCB with plated holes
  • Easy build, dense but straightforward
  • Available assembled or as a full kit (everything included)




1 Output level Potentiometer that sets the signal level to the output stage


2 Signal/Clip LED Flashes green when a signal is present and turns red 3 dB before clipping


3 Gain switch The first 2 positions bypass the input stage. In combination with the level potentiometer the overall gain can be set between 0 and +70dB


4 Polarity Sets the polarity (phase) of the output signal


5 Sends phantom power to the microphone


6 High impedance input (> 1 megohm) for instruments. The instrument signal goes through both transformers.

What's in the kit?

Absolutely everything!

  • Passive components (resistors, capacitors),
  • 2 Carnhill transformers
  • Active components (diodes, transistors, LED, ...),
  • Front panel elements (switches, potentiometers, knobs),
  • Connectors, relay,
  • PCB's,
  • Front panel and side panel,
  • All hardware


You bring the solder (use good quality solder, 1mm diameter max) and the Lunchbox.


Difficulty level

The MP573 kit is an easy build in spite of a rather large number of components.

The only setup is adjusting the bias current in the output stage. It requires a standard DC voltmeter.



Technical specifications

Measure Conditions Value
Iddle supply current No input signal

V+ : +92mA

V- : -92mA

Input impedance f=1kHz
Maximum input level   limited by input TX :
Maximum output level before clip f=1kHz +27dBu
Minimum gain   0dB
Maximum gain   +70dB
EIN Zin=0Ω
Frequency response Gain=+40dB
Deviation < 1dB
THD f=1kHz
< 0.008%
DI input impedance   > 1MΩ
DI gain range   -22dB to +48dB
DI max input level   +15dBu


Technical documents

MP573 Parts list (PDF)

MP573 Component layout (PDF)

MP573 Assembly guide (PDF)

Di01 Assembly guide (PDF)

MP573 Test and setup guide (PDF)

MP573 Schematic (PDF)

DIY guide (PDF)