# Pro-Ject Phono Box S3 B vs Rega Fono MM Mk5: specs and price compared

A sourced, side-by-side comparison of the Pro-Ject Phono Box S3 B (Pro-Ject Audio Systems) and Rega Fono MM Mk5 (Rega) among phono preamps.

## Side by side

| Spec | Pro-Ject Phono Box S3 B | Rega Fono MM Mk5 |
| --- | --- | --- |
| US price | not published | not published |
| Brand | Pro-Ject Audio Systems | Rega |
| Cartridge support | MM and MC | MM only |
| Gain (dB) | 40/45/60/65 dB, plus an additional +6 dB available via the balanced XLR outputs | 41.4 dB @ 1 kHz |
| Snr (dB) | MM: 103/110 dB(A); MC: 85/90 dB(A) | — |
| Riaa accuracy | <0.3 dB (20 Hz - 20 kHz) | better than ±0.2 dB (100 Hz - 100 kHz) |
| Input capacitance pf | 50/150/300/400 pF selectable | 100 |
| Subsonic filter | 20 Hz, 18 dB/octave rolloff | — |
| Thd percent | MM: <0.001% @1kHz, <0.008% 20Hz-20kHz; MC: <0.005% @1kHz, <0.01% 20Hz-20kHz | — |
| Output level | Balanced XLR and single-ended RCA outputs | 200 mV at 1.7 mV input; 200 ohm output impedance |

## Key differences

- Cartridge support: Pro-Ject Phono Box S3 B MM and MC vs Rega Fono MM Mk5 MM only
- Gain (dB): Pro-Ject Phono Box S3 B 40/45/60/65 dB, plus an additional +6 dB available via the balanced XLR outputs vs Rega Fono MM Mk5 41.4 dB @ 1 kHz
- Riaa accuracy: Pro-Ject Phono Box S3 B <0.3 dB (20 Hz - 20 kHz) vs Rega Fono MM Mk5 better than ±0.2 dB (100 Hz - 100 kHz)
- Input capacitance pf: Pro-Ject Phono Box S3 B 50/150/300/400 pF selectable vs Rega Fono MM Mk5 100
- Output level: Pro-Ject Phono Box S3 B Balanced XLR and single-ended RCA outputs vs Rega Fono MM Mk5 200 mV at 1.7 mV input; 200 ohm output impedance

## Sources

- Pro-Ject Phono Box S3 B: https://www.project-audio.com/en/product/phono-box-s3-b/ (project-audio.com, verified 2026-08-12)
- Rega Fono MM Mk5: https://www.rega.co.uk/products/fono-mm-mk5 (rega.co.uk, verified 2026-08-12)

Canonical: https://frontdeskreview.com/gear/phono-preamps/pro-ject-phono-box-s3-b-vs-rega-fono-mm-mk5/
Cite: Per The Front Desk Review, Pro-Ject Phono Box S3 B (not published) vs Rega Fono MM Mk5 (not published) — sourced spec-by-spec comparison at https://frontdeskreview.com/gear/phono-preamps/pro-ject-phono-box-s3-b-vs-rega-fono-mm-mk5/
License: CC BY 4.0.