Muffsy MC Head Amp

A DIY Dual Mono MC cartridge preamplifier for your record player

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A kit for this project is available on Tindie:

The Muffsy MC Head Amp is a dual mono active step-up preamp for LOMC cartridges. The purpose of a head amp is to allow low output MC cartridges to be used with a standard MM phono stage, such as the Muffsy Phono Preamp.

The Muffsy MC Head Amp has the same pitch black, silent background, the great sound stage and revealing sound quality that the Muffsy Phono Preamp is known for.

It uses an ultra-low noise op amp with a DC servo to amplify the LOMC's signal to an MM level. The input impedance is configurable from 47 to 100 ohms in 4 steps.

The PCB is designed to slide into a B0905 cabinet together with the Muffsy Dual Power Supply.

A back panel is also available, in order to make a fully working head amp without any

Kit available:

Design goals:

  • Make a complete, nothing missing, DIY kit (the kit is now available, see
  • Dual mono topology
  • Price target: USD 79
  • Easy and understandable build documentation
  • SNR above 70 dB (referenced to 0.5 mV input)
  • Variable input impedance
  • DC servo to eliminate input/output capacitors
  • Gain of 24.6 dB - 0.3 mV input gives 5 mV output (0.5 mV in: 8.5 mV out), at 1 kHz
  • No power cables across the signal paths
  • Dual layer PCB, immersion gold plated
  • PCB width: 84.0 mm / 3.3 in
  • Make the complete head amp with PSU fit in a B0905 enclosure
  • Improved back panel

Project Status:


  • Topology: Dual mono
  • Gain: 24.6 dB
  • Input impedance: 47 - 100, or 50 - 300 ohms in 4 steps, or choose your own values
  • THD: < 0.1 % *)
  • THD+N: < 0.1 % *) (measured: 0.6 %)
  • SNR: 71.8 dB
  • Frequency Response: +0 / -0.1 dB (20-20.000 Hz)
  • IMD (ITU-R): 0.001 %
  • Dynamic range (referenced to 0 dBV output): > 110 dB
  • Power requirements: +/- 15V at < 40 mA
  • PCB Size: 84.0 x 59.4 mm / 3.3 x 2.3 in

*) The inherent noise and harmonics in my signal generator is too high too accurately measure the THD and THD+N at these low levels. The numbers are too high, both should be well below 0.1% as the measurement without the noise shows that. I've added my measurements for reference anyway.


Input Impedance Calculator

sheet - 38.06 kB - 09/28/2016 at 10:22


  • 1 × PCB Complete kit available at
  • 2 × 47 ohm Resistor 0.25W, 1% metal film
  • 2 × 100 ohm Resistor 0.25W, 1% metal film
  • 2 × 150 ohm Resistor 0.25W, 1% metal film
  • 4 × 220 ohm Resistor 0.25W, 1% metal film

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skrodahl wrote 09/17/2016 at 18:41 point

All ground points are connected on both the top and the bottom ground, so it's more or less like connecting ground planes with vias.

The final version of the Muffsy MC Head Amp is now tested, and there's not even a hint of grounding problems:

  Are you sure? yes | no

Felipe Navarro wrote 09/17/2016 at 18:35 point

You are using ground on top and bottom side of the board. It can make ground loops. :(

  Are you sure? yes | no

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