Why Your Turntable Needs a Phono Preamp
A turntable cartridge produces a very small electrical signal — far weaker than what a standard line-level input on an amplifier expects. A phono preamplifier (or phono stage) does two jobs: it amplifies that tiny signal to line level, and it applies a specific equalization curve (the RIAA curve) that corrects the way audio is encoded on a vinyl record.
Without a phono preamp, your records will sound thin, quiet, and bass-light. But not all phono preamps are the same — and the type of cartridge you use determines what kind of preamp you need.
Moving Magnet (MM) Cartridges
MM cartridges are the most common type, especially in mid-range and budget turntables. They work by moving a small magnet attached to the stylus past a fixed coil, generating a relatively strong output voltage (typically 2.5–5mV).
Because of this higher output, MM cartridges require less amplification from the phono stage — making MM phono preamps simpler and less expensive to build well. Most built-in phono stages (in amplifiers and turntables) are MM-only.
Moving Coil (MC) Cartridges
MC cartridges flip the design: a tiny coil moves while the magnet stays fixed. This lighter assembly tracks the groove more accurately, potentially retrieving more detail from the record. However, MC cartridges produce a much lower output voltage (often 0.2–0.5mV), which requires significantly more amplification from the phono stage.
MC phono stages (or MC-capable phono stages with a switchable gain setting) are more complex and generally more expensive as a result.
Key Differences at a Glance
| Feature | MM Cartridge | MC Cartridge |
|---|---|---|
| Output Voltage | 2.5–5 mV (high) | 0.1–0.5 mV (low) |
| Phono Gain Required | ~40 dB | ~60–70 dB |
| Stylus Replacement | User-replaceable | Usually requires retipping |
| Typical Price Range | $20–$500+ | $100–$5,000+ |
| Sound Character | Warm, musical, forgiving | Detailed, extended, dynamic |
Built-In vs. External Phono Preamp
Many amplifiers and turntables include a built-in phono preamp. For casual listeners, this is perfectly adequate. But a dedicated external phono stage offers several advantages:
- Better component quality in a dedicated circuit, away from electromagnetic interference from other amp components.
- Adjustable loading and gain, which is particularly useful for MC cartridges.
- Upgrade flexibility — you can swap your phono stage independently of the rest of your system.
Cartridge Loading: Why It Matters for MC
MC cartridges are sensitive to the input impedance of the phono stage — a parameter called cartridge loading. The wrong loading can cause high-frequency brightness or roll-off. A good MC phono preamp allows you to adjust the input impedance (common values: 100Ω, 200Ω, 470Ω, 1kΩ) to suit your specific cartridge. This is something your amplifier's built-in MM stage simply cannot do.
Which Should You Choose?
If you're starting out or have a mid-range turntable, a quality MM phono preamp will serve you excellently and is far more affordable. If you've invested in a higher-end turntable and MC cartridge, matching it with a capable MC phono stage is essential to getting the performance you've paid for. Many phono preamps now support both MM and MC, making them a versatile long-term investment.