Noise Measurements - Muffsy Phono Preamp PP-3

Here are some noise measurements of the Muffsy Phono Preamp PP-3.

As you'll see, the noise floor of the Muffsy Phono Preamp PP-3, powered by the Muffsy Hifi Dual Power Supply, is well below -100 dB. The average of all measured points, from 20-20.000 Hz is -107.74 dB and the highest single harmonic is at 92.11 dB. 

Together with the RIAA compliance of +/- 0.025 dB, adjustable input impedance, variable gain, optional input capacitance and the various way you can customize your build, the Muffsy Phono Preamp is a real little performer!

The measurements are taken with a Rigol DG1022 function generator feeding a 1kHz/5mVpp signal into the phono stage. The PP-3's output signal is recorded using a Behringer UCA202 soundcard, and the FFT is generated from that recording. 16.384 measurement points have been recorded, almost 1 measurement per Hz.

The measurements are done without any calibration, on a relatively cheap USB sound card with a whole range of error sources that will provide less than optimal values.

Notice that there is a 50 Hz distortion in the graph (all the small peaks below the high 1 kHz signal). That's unfortunately from the power cable that is running across the input of the PP-3 inside the B-0509 cabinet.

There is also a slope from 10-200 Hz. This slope is identical if I use the Behringer to measure the Rigol DG1022 directly. It probably stems from the DC blocking high-pass filter in the sound card.

Finally, the abrupt slope at 20 kHz is the bandwidth of the sound card. It can only measure up to that level.

Here are some numbers:

• The average level of all measured points is -107.75 dB (20-20.000 Hz), including the 50 Hz distortion and the less than ideal measurements up to 200 Hz. This does not include the steep roll-off at frequencies above 20 kHz.
  
• The highest peak is at 100 Hz, coming in at 88.6 dB. That value can be disregarded as it comes from my power cabling running to close to the phono stage input
• Harmonics:
• 1st (2 kHz): -92.11 dB
• 2nd (3 kHz): -100.38 dB
• 3rd (4 kHz): -98.85 dB