Phono preamp gain and loading, explained by someone who'd rather not own a turntable

A reader emailed me last month asking why his mate's turntable "sounds thin and hissy" through an identical amp to his own. Same cartridge, same records, same room. Turned out the amp had a switchable phono stage set to the wrong gain and loading for the cartridge fitted. Twenty seconds with a screwdriver-sized dip switch and it was a different system. I don't own a turntable — I'll get that out of the way early, it's Priya's and Dave's patch more than mine — but gain staging and impedance loading are pure signal-chain engineering, and that's squarely where I live. So consider this the digital guy's guest pass into analogue territory, focused on the bit that's actually electronics, not ritual.

The reason this trips people up is that a phono stage isn't really one job. It's two: amplify a very small, very variable signal by a very large amount, and undo a frequency-response curve that was baked into the record on purpose. Get the gain wrong and you're either drowning in hiss or clipping on loud passages. Get the loading wrong and the frequency response tilts in ways that mimic a "bad" cartridge when the cartridge was never the problem.

Why phono gain is a different problem to line-level gain

Every other source in your rack — a streamer, a CD transport, a DAC — outputs somewhere around 2 volts RMS at line level. It's a broadly standardised figure, which is why line-level gain staging is mostly a non-issue; your amplifier's input stage is designed around that range and everything just works.

A phono cartridge is nothing like that. A moving-magnet (MM) cartridge typically outputs somewhere in the 3–6 millivolt range. A moving-coil (MC) cartridge, because the coil is lighter and moves less material, often outputs a fraction of that — anywhere from about 0.2mV up to 2.5mV depending on whether it's a high-output or low-output design. That's a difference of two, sometimes three orders of magnitude between what a phono stage has to amplify and what a line stage has to amplify. A phono stage for MM typically applies something like 30–40dB of gain. For low-output MC, you're often looking at 60–70dB. That's the difference between turning a whisper into a conversation and turning a whisper into a shout heard across a stadium.

Get too little gain for your cartridge and you compensate by turning the volume knob further up, which brings the phono stage's own noise floor up with it — hiss, hum, the works. Get too much gain and loud transients (a cymbal crash, a horn stab) clip the input stage before the volume knob even gets involved. Neither is a cartridge problem. Both look exactly like one if you don't know what to check.

MM versus MC: not a hierarchy, a different electrical animal

I hear a lot of "MC is better than MM" talk that treats it like a tier list. Electrically it's not a value judgement, it's a completely different generator design with different output characteristics and different loading requirements. MM cartridges use a moving magnet against fixed coils; they're relatively high output, relatively high internal impedance, and were designed around a specific, standardised load. MC cartridges move the coil itself, which is lighter and faster but produces a much smaller signal at low impedance.

This matters for buying decisions too. If you're assembling a front end and trying to decide where the phono stage sits in your budget, it's worth reading our piece on how to build a vinyl front-end alongside this one — the honest answer is that a mismatched load on a good cartridge will underperform a well-loaded budget one, every time.

Loading: the setting nobody explains properly

Resistive loading is the one that trips people up hardest because it doesn't intuitively map to "more" or "less" the way gain does. For MM cartridges, the industry-standard load is 47kΩ in parallel with some amount of capacitance, usually somewhere between 100pF and 200pF once you account for cartridge, cable and phono stage input capacitance combined. That 47k figure isn't arbitrary; it's what MM cartridge generators were designed against for decades, and manufacturers still spec their frequency response assuming it. Deviate from it substantially and you get a subtly rising or falling top end depending on which way you've moved. Capacitance is the sneaky variable here, because it's not just what your phono stage sets — it's cumulative, from the cartridge's own inductance interacting with total capacitance in the cable plus the phono input. Too much capacitance and MM cartridges can develop a resonant peak in the upper treble, which reads as brightness or edge that isn't actually in the recording.

MC cartridges load completely differently — resistively, generally lower, often between 100Ω and 1k� depending on the specific coil design, with the cartridge manufacturer's spec sheet as the actual source of truth rather than a universal standard. This is the bit that catches people out moving from MM to MC for the first time: the 47k default that worked fine for years is now actively wrong, potentially by two orders of magnitude, and will produce a rolled-off, dull-sounding presentation that gets blamed on the new cartridge rather than the mismatched load.

The practical fix is straightforward, if a little tedious: check the cartridge manufacturer's recommended loading figure, not a forum consensus number, and set your phono stage to match it as closely as the available switch positions allow. Units like the RME ADI-2 DAC FS (check price) aren't phono stages, obviously, but they're a good example of the same underlying philosophy I'd want in a phono preamp — expose the actual engineering parameters to the user instead of hiding them behind vague "warm/bright" toggles.

RIAA equalisation isn't optional, and it isn't a "sound" you're choosing

Here's the bit that I think gets under-explained. Records are cut with a deliberate frequency-response curve — bass reduced, treble boosted — because without it, the groove would need to be enormous to carry low-frequency information, and surface noise would dominate the top end. The RIAA curve, standardised by the Recording Industry Association of America and adopted globally since the late 1950s, undoes this precisely on playback. A phono stage's equalisation network isn't a tone-shaping feature you can treat like a loudness button; it's correcting something that was intentionally distorted at the cutting lathe, and it needs to be accurate to within a fraction of a dB across the audible band or the tonal balance of every record you own tilts in the same direction. This is worth knowing because some cheaper all-in-one phono stages get the RIAA curve close but not exact, and it shows up as a system-wide characteristic — everything sounds slightly bass-light or slightly bright — that people chase with cable changes or cartridge upgrades instead of just measuring the phono stage itself.

Where separates start earning their keep

Built-in phono stages in integrated amps are frequently MM-only, fixed-loading affairs, and that's a legitimate design compromise for a product that has to do six other things too. The Rega Brio Mk7 (check price) and Cambridge Audio CXA81 MkII (check price) both include phono stages that are genuinely usable for MM cartridges without apology, which is more than I can say for a lot of amps in that bracket. But if you're running a low-output MC cartridge, or you want to dial in loading precisely rather than pick between two switch positions, a standalone phono stage is where the actual flexibility lives. It's the same logic that applies to our piece on DAC output stages — the specialised, single-purpose box usually beats the do-everything one when the electrical requirements get demanding.

I'll admit a mild bias here, and it's the contrarian bit: I think a lot of money gets spent on cartridge upgrades that would be better spent getting loading and gain dialled in properly first. A $150 MM cartridge correctly loaded will out-perform a $600 cartridge fighting a mismatched load every single time, and nobody wants to hear that because a new cartridge is a more exciting purchase than adjusting a dip switch.

A practical checklist, for the electronically minded

If you're troubleshooting a system that sounds thin, harsh, hissy or oddly rolled-off, work through it in this order. First, confirm MM or MC and whether your phono stage actually supports the type fitted — plenty of budget stages are MM-only and will technically "work" with an MC cartridge at wildly wrong gain. Second, check the cartridge manufacturer's spec sheet for recommended loading, not a generic online figure. Third, set gain so that a healthy listening level sits comfortably below where your volume control lives at maximum — if you're at 90% volume for normal listening, gain is too low; if you're below 20%, it's likely too high and clipping risk goes up. Fourth, if the phono stage has adjustable capacitance loading for MM, start at the manufacturer's spec and only move if you hear a specific, describable problem like edginess on massed strings or sibilance on vocals. None of this requires golden ears. It requires a spec sheet, a small screwdriver, and the patience to change one variable at a time rather than three at once, which is the bit most people skip.

The bit where the digital and analogue worlds actually agree

I spend most of my working life thinking about bit-perfect transport, jitter, and DAC output stages — genuinely different physics to a cartridge riding a groove. But the underlying discipline is identical: match source output to input stage correctly, and the rest of the chain has a fighting chance. Mismatch it, and no amount of downstream gear fixes what's already gone wrong at the first stage. It's the same reason I keep telling people that a well-configured budget streamer beats a poorly configured expensive one — the principle transfers cleanly across the analogue/digital divide even if the electronics don't. For further reading on the actual standard, the Recording Industry Association of America's technical documentation on the RIAA equalisation curve is the primary source, and it's a useful sanity check if you ever want to verify a phono stage's claimed accuracy against the original spec.

Vinyl's never going to be my main format — I like knowing exactly what bits left the file and exactly what bits reached the DAC, and analogue playback doesn't offer that kind of certainty. But there's no folklore in gain and loading. It's Ohm's law and a frequency-response curve from a standards document. Get it right and the format's genuine strengths — the top end, the way transients feel — actually show up, instead of being buried under noise or tilted by a mismatched impedance nobody thought to check.