Passive Preamplifiers and Step-Up Transformers: The Complete Audiophile Guide

Published by IWISTAO

In the world of high-fidelity audio, the signal chain from stylus to speaker is everything. Yet few components are as misunderstood — or as quietly transformative — as the passive preamplifier and its close cousin, the step-up transformer (SUT). Unlike active preamps that rely on transistors or tubes to amplify voltage, these passive devices achieve gain through purely electromagnetic means: no batteries, no power supplies, no active noise sources. The result, when done well, is a sonic transparency that active circuits often struggle to match.

This guide explores both technologies in depth — from the physics of transformer action to the practical art of matching a SUT to a low-output moving-coil (LOMC) cartridge.

1. What Is a Passive Preamplifier?

A passive preamplifier — sometimes called a passive linestage or passive control unit — is a volume and source-selection device that contains no active gain stage. It typically consists of:

• A precision attenuator (resistive potentiometer, ladder network, or transformer-based)
• Source selector switch(es)
• Input and output connectors

Because it introduces no gain, a passive preamp works on the assumption that the source component (a CD player, DAC, or phono stage) already provides sufficient output voltage to drive a power amplifier directly — typically 1 V RMS or more. Modern solid-state sources almost always satisfy this requirement.

1.1 Resistive Passive Preamps

The simplest passive preamp is a metal-film potentiometer or a discrete resistor ladder (switched attenuator) wired between source and amplifier. Advantages include dead-flat frequency response and extremely low distortion. The critical limitation is impedance interaction: a high source impedance combined with a low input impedance on the power amplifier creates a voltage-divider effect that varies with pot position, causing frequency response anomalies and loss of bass weight at lower volume settings.

1.2 Transformer-Based Passive Preamps (TVC)

A transformer volume control (TVC) replaces the resistor attenuator with a transformer whose secondary has multiple taps. Selecting different taps changes the voltage ratio — and therefore the volume — while maintaining a low impedance at all attenuation levels. The transformer also provides galvanic isolation between source and amplifier. Lundahl, Stevens & Billington, and Dave Slagle's EMIA designs are well-regarded in this category.

Figure 1 — Signal flow in a passive preamplifier system. No active gain stage exists between source and power amplifier.

2. Step-Up Transformers (SUT) — The Basics

A step-up transformer in the phono context is a small, precision audio transformer placed between a low-output moving-coil (LOMC) cartridge and a Moving-Magnet (MM) phono stage. Its job is to raise the tiny LOMC signal — often 0.2–0.6 mV — to the 2–5 mV level expected by a standard MM phono input.

2.1 Faraday's Law and Transformer Action

The operating principle of all transformers is Faraday's Law of electromagnetic induction: a changing magnetic flux through a coil induces a proportional electromotive force (EMF). When two coils share a common core, energy is transferred from primary to secondary through the changing magnetic field.

The fundamental relationships are:

• Voltage ratio: V_s / V_p = N_s / N_p = n (turns ratio)
• Current ratio: I_s / I_p = N_p / N_s = 1/n (current steps down as voltage steps up)
• Impedance transformation: Z_s / Z_p = (N_s / N_p)² = n²

For a SUT with a 1:10 turns ratio (n = 10), a 0.3 mV cartridge signal becomes 3 mV at the secondary — a voltage gain of 20 dB. Simultaneously, the source impedance seen at the secondary is multiplied by n² = 100.

Figure 2 — Simplified step-up transformer circuit. The MC cartridge feeds the primary; the amplified signal appears at the secondary, driving a standard MM phono stage. A 1:10 ratio transforms 0.3 mV → 3 mV.

3. Why Use a Step-Up Transformer?

The question is valid: a high-quality, low-noise MC phono stage can amplify an LOMC signal without a SUT. Why bother with a transformer at all? The answer lies in the noise floor.

3.1 The Noise Advantage

A SUT provides passive voltage gain — it raises the signal level without introducing active device noise; the remaining noise is dominated by winding resistance and source impedance. An active amplifier, by contrast, always adds its own noise. The key metric is Equivalent Input Noise (EIN):

• A typical low-noise op-amp (e.g., NE5534) has an EIN of about −120 dBu
• A precision bipolar transistor stage (e.g., 2SB737 in Denon's classic phono stages) can reach −140 dBu
• A quality SUT + MM stage effectively "pre-amplifies" passively, so the noise floor referenced to the cartridge output is determined almost entirely by the winding resistance — not by an active device

For a cartridge outputting 0.2 mV, even a 3 dB difference in noise floor is clearly audible as a quieter, blacker background.

3.2 Impedance Matching

A moving-coil cartridge is a low-impedance source — typically 2–40 Ω. For optimal loading for noise performance and frequency response (rather than maximum power transfer), the load presented to the cartridge should ideally be 5–10× the cartridge's internal impedance. A SUT automatically performs this matching: a 1:10 transformer reflects the 47 kΩ MM load back to the primary as 47 kΩ / 100 = 470 Ω — well suited for a 10–40 Ω MC cartridge coil.

3.3 Galvanic Isolation and Ground Loops

Because primary and secondary coils are electrically isolated, a SUT naturally breaks ground loops between turntable and phono stage. Cartridges with chassis-connected grounds benefit greatly; many audiophiles report a dramatic reduction in hum and RF interference after inserting a SUT.

"When I added a quality SUT to my LOMC setup, the noise floor dropped so significantly that I could hear details in familiar recordings I simply hadn't noticed before — decay tails in reverb, the scrape of chair legs, the breath before a vocal phrase."

— A common sentiment in audiophile forums, echoing decades of SUT adoption

4. Key SUT Design Parameters

4.1 Turns Ratio Selection

The turns ratio is the most critical selection parameter. Common ratios available in commercial SUTs are 1:5, 1:10, 1:20, and 1:30. The correct ratio depends on the cartridge's output voltage:

Cartridge Output	Recommended Ratio	Voltage Gain	Gain (dB)
0.4 – 0.6 mV (Med-High MC)	1:5	×5	+14 dB
0.2 – 0.4 mV (Standard LOMC)	1:10	×10	+20 dB
0.1 – 0.2 mV (Very Low MC)	1:20	×20	+26 dB
<0.1 mV (Ultra-Low MC)	1:30 – 1:40	×30–40	+30–32 dB

The goal is to raise the signal to approximately 2–5 mV at the MM phono input — enough for the MM stage's gain to work optimally without saturation.

⚠️ Avoid Over-Driving Using too high a turns ratio with a medium-output MC can overdrive the MM phono stage, causing clipping on dynamic transients. A 0.5 mV cartridge through a 1:30 SUT produces 15 mV — potentially saturating a MM stage designed for a 5 mV maximum.

4.2 Core Material

The core material determines frequency bandwidth, saturation level, and distortion. The three main options are:

• Silicon steel (grain-oriented, GOSS) — Economical, good saturation, but limited high-frequency extension. Common in budget SUTs.
• Permalloy (Ni-Fe alloy, e.g., Mumetal) — Very high permeability (μ up to 100,000), low-frequency extension to sub-1 Hz, low core losses. Used in high-end designs (Lundahl LL1931, Bob's Devices). Sensitive to mechanical stress.
• Amorphous alloy (e.g., Metglas) — Extremely low hysteresis loss, wide bandwidth. Used in top-tier modern SUTs (Hashimoto HM-7, some Cinemag designs).
• Nanocrystalline (Vitroperm 500F) — Highest permeability, widest bandwidth, lowest distortion. Increasingly popular in audiophile-grade designs.

4.3 Winding Geometry and Shielding

At the tiny signal levels involved (microvolts to millivolts), electromagnetic interference (EMI) pickup is a serious concern. High-quality SUTs address this through:

• Electrostatic (Faraday) shielding between primary and secondary — a grounded copper foil layer that blocks capacitively coupled noise
• Mumetal enclosures — the transformer case itself is made from high-permeability alloy, attenuating magnetic field ingress from power transformers or motors
• Interleaved winding — alternating layers of primary and secondary reduce leakage inductance and extend high-frequency response

4.4 DC Resistance and Insertion Loss

Every winding has resistance (DCR). The primary DCR adds in series with the cartridge, forming a resistive divider with the secondary-reflected load. A high DCR relative to the cartridge's internal impedance causes:

• Reduced voltage transfer (insertion loss)
• Increased noise floor
• Possible bass rolloff if primary inductance is also low

Quality SUTs keep primary DCR below 5–10 Ω; premium designs achieve under 1 Ω using heavy-gauge, high-purity copper winding wire.

5. Frequency Response, Bandwidth & Loading

An ideal transformer has flat frequency response from DC to infinity. In practice, two mechanisms limit bandwidth:

• Low-frequency rolloff: determined by primary inductance (L_p). Below the LF cutoff (f_L = (R_source + R_reflected) / (2πL_p)), response falls. A permalloy core can achieve L_p > 100 H, pushing f_L below 1 Hz even with a 40 Ω source.
• High-frequency rolloff: caused by leakage inductance (L_lk) and inter-winding capacitance. Good interleaved designs extend −3 dB bandwidth to 100 kHz or beyond.

5.1 The Loading Resistor

The resistive load at the secondary (typically the 47 kΩ MM input impedance) is transformed to the primary as Z_p = 47 kΩ / n². An optional parallel loading resistor can be placed at the secondary to fine-tune the effective load on the cartridge. This affects both frequency response and the damping of resonance peaks in the cartridge/arm system.

A useful rule of thumb: start at the manufacturer's recommended cartridge load, calculate what secondary resistor achieves that, and adjust by ear. Many experienced audiophiles find that loading a SUT slightly heavier than theory suggests results in better tracking behavior on sibilants.

Figure 3 — Impedance reflection through a 1:10 SUT. The 47 kΩ MM phono input appears as 470 Ω at the primary — a suitable load for a 10–40 Ω MC cartridge.

6. Notable Step-Up Transformer Manufacturers

The SUT market spans a wide range from budget-friendly Japanese vintage units to contemporary artisan designs. Here is an overview of key players:

Brand / Model	Country	Core Material	Ratio(s)	Approx. Price	Notes
Lundahl LL1931	Sweden	Permalloy (C-core)	1:8, 1:16, 1:32	~$300–500 (DIY)	Industry reference; exceptional bandwidth and low DCR
Hashimoto HM-7	Japan	Permalloy	1:10, 1:20	~$400–600 (DIY)	Traditional Japanese craftsmanship; smooth, natural tone
Bob's Devices Sky 20	USA	Cinemag (Permalloy)	1:20	~$900	Mu-metal shielded; widely reviewed; very quiet
Ortofon T-5 / T-20	Denmark	Permalloy	1:5, 1:20	~$400–700	Matches Ortofon MC cartridges natively
Denon AU-320 / AU-340	Japan	Silicon steel	1:10, 1:40	$80–300 (vintage)	Classic vintage design; excellent value for budget builds
Audio Note AN-S2 / S3	UK	Silicon steel (grain-oriented)	1:10	~$600–1200	Used with Audio Note MC cartridges; silver winding option available
Stevens & Billington TX-103	UK	Mu-metal, Permalloy	1:10, 1:20	~$500–900	Used in TVC designs; excellent shielding
Jensen JT-44K-DX	USA	Permalloy	1:10	~$350 (DIY)	Broadcast-grade; very flat response; used in pro and audiophile contexts

7. Matching a SUT to Your MC Cartridge — Practical Guide

7.1 Step-by-Step Selection

1. Find your cartridge's output voltage. Check the manufacturer's datasheet. Typical LOMC values: 0.2–0.6 mV.
2. Determine target MM input level. Most MM phono stages work best with 2–5 mV input. Choose a ratio: target_mV / cartridge_mV (e.g., 4 mV / 0.3 mV ≈ 13×, so a 1:10 or 1:12 ratio is appropriate).
3. Calculate the effective load. Z_primary = 47 kΩ / n². Compare this to the cartridge manufacturer's recommended load impedance.
4. Check for compatibility. Some cartridges are "transformer-unfriendly" — very low internal impedance (<2 Ω) can cause instability. Consult the manufacturer. Cartridges such as the Denon DL-103 (40 Ω) are extremely SUT-friendly.
5. Listen and adjust secondary loading. Add a resistor in parallel with the MM input to change effective cartridge load. Try 100 Ω, 470 Ω, and 1 kΩ secondary resistors and compare tracking on complex piano passages or high-frequency string harmonics.

7.2 Common Mismatches and Symptoms

Symptom	Likely Cause	Fix
Bright, harsh treble; sibilance distortion	Cartridge under-loaded (too high impedance seen at primary)	Add secondary loading resistor to reduce effective Z
Dull, rolled-off highs	Excessive capacitive loading from cable; core resonance with loading	Shorten interconnect; reduce secondary loading resistor value
Soft, loose bass; lack of punch	Primary inductance too low for cartridge impedance (LF rolloff)	Switch to higher-permeability core; use SUT with larger core cross-section
Midrange hum or 50/60 Hz noise	Insufficient magnetic shielding; bad ground connection	Improve shielding; ensure signal ground continuity; orient SUT away from power transformer
Clipping / distortion on loud passages	Ratio too high; MM stage overdriven	Switch to lower ratio SUT

8. Passive vs. Active Preamplifier: A Balanced Comparison

The passive vs. active preamp debate has divided audiophiles for decades. Neither approach is universally superior — the choice depends on system context.

Parameter	Passive Preamp (Resistive)	TVC (Transformer Volume Control)	Active Preamp (Tube or Solid-State)
Signal Gain	Attenuation only (≤0 dB)	Attenuation; some designs offer slight gain	Typically +6 to +26 dB
Noise Floor	Excellent (no active devices)	Excellent; isolation from external noise	Adds amplifier noise; depends on design quality
Output Impedance	Varies with attenuation (can be high at mid-volume)	Low at all settings (transformer driven)	Low (solid-state) or moderate (tube)
Cable Sensitivity	High — long cables degrade response	Moderate — transformer output is more robust	Low — buffered/low-Z output drives cables easily
Distortion	Near-zero (resistive only)	Very low; some core saturation possible at extremes	Depends on design (tube 2nd harmonic, SS near-zero)
Power Required	None	None	Yes (transformer, heaters for tubes)
Ideal Application	Short cables; high-output sources; insensitive power amp input	Flexible use; best transparency with isolation	Long cable runs; low-output sources; any power amp
Typical Cost	$100 – $2,000+	$500 – $10,000+	$200 – $50,000+

"A passive preamp with a quality power amplifier and a modern high-output source is arguably the shortest path between a digital file and your ears. Whether that translates to the most musical result is a question only your system — and your ears — can answer."

9. The Transformer Volume Control (TVC) — Deep Dive

The TVC is a fundamentally different topology from both resistive passive preamps and active linestages. A transformer with a multi-tap secondary allows the volume to be set by selecting the ratio of turns between primary and the chosen secondary tap.

Figure 4 — Transformer Volume Control (TVC): selecting different secondary taps changes the turns ratio, varying output voltage (volume) while maintaining low output impedance at all settings.

The TVC's key advantage over a resistive attenuator is that its output impedance remains low across all attenuation levels (though not strictly constant). A pot's output impedance peaks at mid-position; a TVC's output impedance is always low (it is a transformer secondary, essentially an EMF source). This makes TVC-based passive preamps far more compatible with cables and power amplifiers over long interconnects.

Notable TVC products include designs by Dave Slagle (EMIA), Intact Audio autoformers, and Sowter custom transformers. The autoformer (single winding with taps, not a dual-winding transformer) is a cost-effective variant that provides the same low-impedance behavior but without galvanic isolation.

10. System Integration Tips

10.1 Placement and Orientation

Place the SUT as close to the turntable as possible to minimize cable length on the low-level MC signal. The SUT is magnetically sensitive — keep it at least 30 cm from power transformers, motor drives, and switching power supplies. If hum is present, rotate the SUT on its axis in 15° increments to find the null orientation in the ambient magnetic field.

10.2 Cable Quality Matters More Here

Between cartridge and SUT, you are dealing with sub-millivolt signals in the microvolt range for the softest musical passages. Any tribological noise (microphony) or dielectric absorption in the cable becomes audible. Shielded, low-capacitance cables with Litz-type conductors and silver or copper foil shields are recommended. Keep cable length under 0.5 m where possible.

10.3 Ground Connections

The SUT chassis ground, cartridge ground, and phono stage ground must form a single, star-grounded connection point. Loops in the ground path are the primary cause of hum in SUT installations. Use the turntable's dedicated ground lug; do not rely on signal ground through the RCA connector alone.

10.4 Break-In Period

Some audiophiles report that permalloy-core transformers may exhibit changes over an initial 50–200 hour usage period, though this is not universally confirmed by engineering measurements. The magnetic domains gradually settle into lower-energy states, and many audiophiles report a progressive improvement in low-frequency weight and midrange liquidity over this period. Allow adequate burn-in before critical listening evaluations.

💡 Practical Tip: Build Before You Buy Before committing to an expensive commercial SUT, consider winding a test SUT on a Lundahl LL1931 core kit — available from DIY audio suppliers. This hands-on experience gives direct insight into how turns ratio and core geometry affect sound, and costs $80–150 in parts.

11. Audio Transformers in the Broader Signal Chain

While this guide focuses on phono SUTs and TVC passive preamps, audio transformers appear throughout the signal chain:

• Output Transformers (OPT) — Used in single-ended and push-pull tube amplifiers to match the high-impedance plate circuit to the low-impedance loudspeaker load. The OPT is arguably the most critical component in a tube amplifier's sonic character.
• Interstage Transformers (IST) — Drive grid-to-cathode between tube stages with galvanic isolation, enabling direct coupling without cathode followers or coupling capacitors.
• Input Transformers — Balanced-to-unbalanced (BAL/UNBAL) conversion in professional audio equipment; also used as grounding and noise-isolation devices.
• Line-Output Transformers — Used in tube DACs and CD players with transformer-coupled outputs to eliminate high-frequency switching artifacts.

Each of these applications places different demands on core material, winding geometry, and DCR — yet the underlying electromagnetic principles are identical.

12. Conclusion

Passive preamplifiers and step-up transformers occupy a unique position in the audiophile toolkit: they are uncompromisingly honest devices that impose almost nothing of their own on the signal, yet the care and precision required to realize that ideal is extraordinary. A well-matched SUT with a quality permalloy core, interleaved winding, and Mu-metal shielding can transform an LOMC cartridge's minuscule signal with a purity that even the best active MC stages struggle to equal — not because active designs are inferior in principle, but because every active component introduces variables that careful transformer design simply avoids.

Whether you are exploring a transformer volume control for a linestage, seeking a SUT to partner a low-output moving-coil cartridge, or simply curious about the physics behind these elegant electromagnetic devices, the journey rewards patience. Start with the fundamentals: understand the turns ratio, choose a core material appropriate for your cartridge's impedance, and listen critically. The physics have been understood for over a century — the art lies in the implementation.

Shop Passive Preamplifiers and Step-Up Transformers

Find More

• Inside the Phono Cartridge: Why MM and MC Use Different Generator Designs — and Often Sound Different
• The Complete Guide to Phono Preamps: Unlocking the Full Potential of Your Vinyl Collection
• The Complete Guide to Vinyl Phono Tonearms: Design, Geometry and Setup
• The Complete Phono Cable Guide: MM vs MC, Capacitance and Shielding
• Passive Preamplifier Audio Signal Boosting Transformer for Smartphone PC CD Player MC Phono Sound Quality Enhancer HIFI

References

1. Millman, J. & Halkias, C. (1972). Integrated Electronics: Analog and Digital Circuits and Systems. McGraw-Hill. [Transformer theory fundamentals, Chapter 17]
2. Ballou, G. (Ed.). (2008). Handbook for Sound Engineers, 4th ed. Focal Press. https://www.routledge.com/…
3. Lundahl Transformers. (2023). LL1931 Datasheet: Moving Coil Step-Up Transformer. https://www.lundahl.se/products/audio-transformers/mc-step-up/
4. Jensen Transformers. (2022). JT-44K-DX Phono Input Transformer Application Notes. https://www.jensen-transformers.com/product/jt-44k-dx/
5. Bob's Devices. (2024). Sky Series SUT Product Documentation. https://www.bobsdevices.com/sky-series/
6. Ortofon A/S. (2023). Technical Background: Moving Coil Cartridges and Step-Up Solutions. https://www.ortofon.com/mc-transformers
7. Slagle, D. (2015). "Autoformer Volume Controls: Theory and Practice." AudiogoN Discussion Forum. https://forum.audiogon.com/discussions/autoformer-volume-controls
8. Broskie, J. (2021). "Step-Up Transformers for Moving-Coil Cartridges." Tube CAD Journal. https://www.tubecad.com/2021/step_up_transformers.html
9. Hagerman, J. (2009). "Phono Preamp Design." HagTech Audio Blog. https://hagtech.com/pdf/phonoeq.pdf
10. Hashimoto Electric Co. (2023). HM-7 & H-7 Step-Up Transformer Specifications. https://www.h-sound.co.jp/hashimoto/trans_mc.html
11. Sowter Transformers. (2024). Type 9335 / 9336 Moving Coil Step-Up Transformer. https://www.sowter.co.uk/specs/9335.php
12. Ortofon SPU Royal GM MkII image. Wikimedia Commons, by RCraig09 (CC BY-SA 4.0). https://commons.wikimedia.org/wiki/File:Ortofon_SPU_Royal_GM_MKII.jpg

The Complete Guide to Phono Preamps: Unlocking the Full Potential of Your Vinyl Collection

Published by IWISTAO

Understanding RIAA Equalization, Circuit Design, Cartridge Matching, and Real-World Design Trade-Offs for High-Performance Vinyl Playback.

 

A phono preamplifier (phono stage) is one of the most critical parts of any vinyl playback system. This specialized amplifier performs two essential functions: it amplifies the tiny millivolt-level signal from a turntable cartridge to a level suitable for a line input, and it applies inverse equalization to compensate for the frequency contour imposed during record mastering. Without adequate gain and accurate playback equalization, a record signal will sound tonally incorrect—typically with weak bass, exaggerated treble, and reduced musical balance. This revised guide explores the technical principles, circuit topologies, component choices, and practical system-matching considerations involved in selecting or building a phono stage that performs well in the real world, not just on paper.

Table of Contents

• 1. Why Do You Need a Phono Preamp?
• 2. Understanding RIAA Equalization
• 3. MM vs MC Cartridges: Technical Differences
• 4. Phono Preamp Circuit Topologies
• 5. Active RIAA Design: Component Calculation
• 6. Cartridge Loading and Impedance Matching
• 7. Noise Considerations and Op-Amp Selection
• 8. Building Your Own Phono Preamp
• 9. Conclusion

1. Why Do You Need a Phono Preamp?

Vinyl records store music in a fundamentally different way than digital formats. The grooves on a record contain physical modulations that represent the audio waveform. As the stylus traces these grooves, the phono cartridge converts mechanical vibrations into electrical signals. However, the signal produced by a phono cartridge is far too weak to be used directly by a conventional line-level input.

 

 

Figure 1: The complete vinyl playback signal chain from record to speakers

 

A typical moving magnet (MM) cartridge produces only a few millivolts of output—commonly around 3-5 mV at the standard test velocity—while low-output moving coil (MC) cartridges often produce just 0.2-0.5 mV. By comparison, consumer line-level inputs usually expect signals that are orders of magnitude higher. As a result, a phono stage typically provides roughly 35-45 dB of gain for MM cartridges and approximately 55-65 dB for low-output MC cartridges, although the exact requirement depends on cartridge output, the desired headroom, and the input sensitivity of the downstream amplifier or preamplifier.

But gain alone is not enough. During record mastering, engineers apply a standard equalization curve that reduces low frequencies and boosts high frequencies. This is done to make record cutting more practical, to reduce groove excursions at bass frequencies, and to improve the noise performance of the medium. During playback, the phono preamp must apply the inverse of that curve—known as the RIAA playback equalization—to restore a more neutral tonal balance.

2. Understanding RIAA Equalization

The Recording Industry Association of America (RIAA) established a playback equalization standard based on three time constants. These define the characteristic turnover frequencies used in conventional RIAA playback equalization:

RIAA Time Constants and Frequencies

Time Constant	Frequency	Recording Action	Playback Compensation
T1 = 3180 μs	50.05 Hz	Low-frequency pre-emphasis limit	Approx. +20 dB/decade recovery below 50 Hz
T2 = 318 μs	500.5 Hz	Midband turnover	Transition region toward midband reference
T3 = 75 μs	2,122 Hz	High-frequency pre-emphasis	Approx. -20 dB/decade cut above 2.1 kHz

Table updated to emphasize standard playback behavior more precisely. The core RIAA playback definition is built on these three time constants.

 

 

Figure 2: The RIAA equalization curve showing recording and playback characteristics

 

The effect of this equalization is substantial: relative to the 1 kHz reference region, playback requires significant low-frequency restoration and high-frequency attenuation. At the extremes of the audio band, the total correction spans many decibels, which means a phono stage must combine accurate equalization with low noise, low distortion, good overload behavior, and stable channel matching.

Key Design Challenge

The RIAA curve requires careful control of component values and topology. Even modest response errors can become audible, and mismatch between left and right channels can degrade stereo imaging. High-performance designs often target very small equalization error—commonly within a few tenths of a decibel across most of the audio band—while the final real-world result still depends on component tolerances, measurement method, and implementation quality.

3. MM vs MC Cartridges: Technical Differences

The choice between Moving Magnet (MM) and Moving Coil (MC) cartridges has a direct effect on phono preamp requirements. The two technologies differ in output voltage, source impedance behavior, loading sensitivity, stylus serviceability, and often in how they are optimized for tracking and transient reproduction.

 

 

Figure 4: Technical comparison of MM and MC cartridge characteristics

Moving Magnet (MM) Cartridges

In an MM cartridge, the stylus moves a magnet relative to fixed coils. This arrangement generally provides a comparatively high output voltage and makes MM cartridges easy to interface with mainstream phono inputs. Many MM designs are specified for a standard 47 kΩ resistive load, but that does not tell the whole story: load capacitance also matters. The cartridge’s inductance interacts with cable capacitance and phono stage input capacitance, which means high-frequency response can change noticeably if the total capacitive load departs from the manufacturer’s recommendation.

• User-replaceable stylus: In many MM and VM designs, the stylus assembly can be replaced without replacing the full cartridge body
• Lower gain requirements: A typical MM stage needs substantially less gain than an MC stage
• Standard loading: 47 kΩ is widely used, but recommended capacitance must also be considered
• Broad market range: Good MM cartridges exist from entry-level to genuinely high-end tiers

Moving Coil (MC) Cartridges

MC cartridges reverse the generator arrangement: the coils move within a magnetic field while the magnet system remains fixed. Because many MC designs use a lighter moving assembly, they are often associated with excellent detail retrieval, fast transient response, and strong tracking performance; however, these sonic and mechanical outcomes still depend on the complete cartridge design, not simply the generator principle alone.

• Very low output: Low-output MC designs often require an additional 15-25 dB of gain beyond MM requirements
• Lower source impedance: Many MC designs have much lower internal impedance than MM cartridges and therefore different noise and loading behavior
• Fixed stylus assembly: Many MC cartridges must be retipped, rebuilt, or replaced when worn
• Higher cost ceiling: MC cartridges span a wide range, from relatively affordable models to very expensive flagship products

Important: Loading Capacitance for MM Cartridges

Many phono preamp schematics show a capacitor—often somewhere in the 100-220 pF range—in parallel with the standard 47 kΩ input resistor. The correct choice is not to omit this capacitor by default, nor to include a fixed value blindly. Instead, total input capacitance should be chosen according to the cartridge maker’s recommended load and the capacitance already contributed by the tonearm cable and wiring. For example, Audio-Technica specifies a recommended load capacitance of 100-200 pF for the VM540ML. In other words, the best design choice is cartridge-specific, not universal.

Example Manufacturer Loading Data

Cartridge / Type	Official or Commonly Cited Load Guidance	Design Implication
Audio-Technica VM540ML (MM/VM)	47 kΩ, 100-200 pF	Total capacitive load matters; cable + phono input must be considered together
Denon DL-103 (MC)	100 Ω or more	Resistive loading is important, but there is no single “correct” ratio rule for all cartridges
Denon DL-103R (MC)	100 Ω min. (40 Ω when using a transformer)	Transformer use changes the effective loading picture and should not be treated the same as active gain

4. Phono Preamp Circuit Topologies

Several circuit approaches can implement RIAA equalization, and no single topology has an absolute monopoly on good sound or good measurements. The designer’s implementation quality matters at least as much as the broad topology label.

 

 

Figure 6: Common phono preamp circuit topologies compared

Passive RIAA Networks

A passive RIAA stage typically places an equalization network between two gain blocks. This can be elegant and conceptually straightforward, and many excellent designs use it successfully. However, because the network itself attenuates part of the signal, the system often requires more total gain and careful attention to noise. The first stage, the equalization network, and the second stage must be considered as a complete system rather than as isolated blocks.

• The network introduces insertion loss, which usually requires additional gain elsewhere
• Noise performance depends heavily on the gain distribution before and after the EQ network
• When properly executed, passive RIAA can still deliver superb measured and subjective performance

Active Feedback RIAA

An active-feedback phono stage incorporates the RIAA network into the feedback loop of an amplifier stage. This can reduce part count, make gain distribution efficient, and produce excellent measured accuracy when the amplifier device has enough open-loop gain, linearity, and stability for the job. It is a highly practical and widely used topology, especially for op-amp-based stages, but it should be regarded as one strong engineering solution rather than the only “correct” one.

• Efficient gain shaping: The equalization is built into the closed-loop behavior of the stage
• Potentially excellent accuracy: Well-chosen values and a stable amplifier can produce very low RIAA deviation
• Implementation-sensitive: Device choice, loop stability, and layout remain critical

 

 

Figure 3: Representative active-feedback RIAA phono preamp topology

Hybrid Tube/Solid-State Designs

Some audiophiles favor hybrid designs that combine tube gain stages with solid-state buffers or regulated support circuitry. These approaches can offer useful electrical benefits—such as reduced output impedance or stronger drive capability—while also appealing to listeners who prefer the subjective harmonic character often associated with vacuum tubes. As always, the final result depends more on implementation than on marketing labels such as “tube warmth” or “solid-state precision.”

• Tube gain stages may be selected for subjective voicing as much as for measured performance
• Solid-state output stages can provide lower output impedance and better cable drive
• Hybrid designs often give the designer broad flexibility in balancing noise, gain, and sonic character

5. Active RIAA Design: Component Calculation

Designing an accurate active RIAA preamp requires careful calculation of component values, plus awareness of which parts of the equalization curve are genuinely standardized and which are optional or design-specific. For standard RIAA playback equalization, the three core time constants remain 3180 μs, 318 μs, and 75 μs.

Standard RIAA playback is defined by three time constants: 3180 μs, 318 μs, and 75 μs.

Some designers also discuss an additional ultrasonic correction sometimes associated with a so-called “Neumann pole” or with cutter-head / cutting-amplifier bandwidth limitations. This is not part of the core three-time-constant RIAA playback standard itself, and it should therefore be treated as an optional design consideration rather than a mandatory requirement in every phono stage.

Design Procedure

Modern design methods can use network synthesis or numerical optimization to calculate practical component values for an active-feedback RIAA stage. A sensible design workflow looks like this:

1. Select a topology and gain target first: Decide whether the stage is intended for MM only, switchable MM/MC use, or as part of a multi-stage front end.
2. Choose capacitor values with availability and tolerance in mind: In a real design, available film capacitor values, matching strategy, voltage coefficient, and thermal behavior matter.
3. Calculate resistor values around the chosen capacitors: Use the selected time constants to derive the appropriate resistive network values for the target response.
4. Verify with simulation and measurement: A mathematically correct nominal design still needs tolerance analysis, loop-stability checking, and measured confirmation on the finished hardware.

Illustrative MM Active RIAA Design Example

Component	Nominal Value	Practical Assembly Note
C₁	3450 pF	May be realized by paralleling standard values for tighter trimming
C₂	1000 pF	Use a stable low-loss dielectric suitable for equalization work
R₁	921.7 kΩ	Series combinations are often used to approach calculated values more precisely
R₂	75.0 kΩ	Can be left as a standard value if the wider network is optimized around it
R₃	1.78 kΩ	Helps set gain and loop behavior in the active network
R₄	2.49 kΩ	Should be checked together with op-amp stability, overload margin, and noise contribution

Values like these can yield an excellent approximation of the RIAA playback curve in theory. In practice, however, the final result depends on resistor and capacitor tolerances, temperature stability, amplifier open-loop behavior, PCB parasitics, and channel matching. For that reason, statements such as “±0.05 dB from 20 Hz to 20 kHz” should be reserved for measured results from a specific completed design rather than assumed solely from the nominal schematic.

6. Cartridge Loading and Impedance Matching

Proper loading is critical for cartridge performance, but loading recommendations should be treated with nuance. Some cartridges are very sensitive to resistive loading, some to capacitive loading, and some to the combined behavior of the entire front-end interface, including cable capacitance, transformer ratio, or input device noise matching.

 

 

Figure 5: Effect of loading impedance on MC cartridge frequency response and electrical damping

Loading Guidelines

• For MM cartridges: Follow both the recommended resistive load and the recommended total capacitive load
• For MC cartridges with active gain: Use the manufacturer’s recommendation as the primary reference rather than relying on a universal impedance-ratio rule
• For step-up transformers: Remember that the reflected load depends on transformer ratio and the impedance seen at the secondary

Recommended Loading for Popular MC Cartridges and Practical Starting Points

Cartridge	Internal Impedance	Manufacturer Guidance / Practical Start
Lyra series	Varies by model	Check factory recommendation; many users begin in the low-hundreds of ohms and fine-tune from there
Koetsu series	Varies by model	Use maker guidance when available; loading is system-dependent and not reducible to one simple ratio
Denon DL-103	40 Ω	Manufacturer literature: 100 Ω or more
Denon DL-103R	14 Ω	Manufacturer literature: 100 Ω min. (40 Ω when using a transformer)
Ortofon MC series	Varies by model	Consult the specific model data; recommended loading may differ substantially across the range

Experimenting with different MC load values can be useful, especially in preamps that offer DIP-switch or jumper selection. However, broad claims such as “lower loads always tighten bass” or “higher loads always sound warmer” are too simplistic. In reality, changing the load primarily affects electrical damping and high-frequency behavior, and the audible outcome varies according to cartridge design, transformer use, front-end noise matching, and the rest of the playback chain.

7. Noise Considerations and Op-Amp Selection

Noise is often the limiting factor in phono preamp performance. With low-output MC cartridges producing only a few tenths of a millivolt, even very small amounts of voltage noise, current noise, hum pickup, grounding contamination, or power-supply residue can become clearly audible. That is why source impedance, topology, grounding, and shielding must be considered alongside the raw op-amp datasheet.

Key Op-Amp Specifications

• Input noise voltage: Especially important in low-output MC applications
• Input noise current: Can become increasingly important as source impedance rises
• Open-loop gain and linearity: Important for equalization accuracy in feedback-based stages
• Bandwidth and stability: Adequate bandwidth is necessary, but there is no single universal GBW threshold that guarantees good phono performance

Recommended Op-Amps and Design Context

For MM cartridges: OPA1656, LME49710, and other low-noise audio devices can work well when the circuit is designed around their strengths.
For low-output MC applications: Designers often consider ultra-low-noise bipolar devices such as AD797 or LT1028, provided the topology and stability requirements are handled correctly.
Important caveat: Device suitability depends strongly on source impedance, gain distribution, topology, and implementation quality—not just on brand reputation or a single headline datasheet number.

Example Device Data Relevant to Phono Design

Device	Useful Published Data	What It Means in Practice
TI OPA1656	Gain-bandwidth product 53 MHz; high open-loop gain 150 dB	Excellent modern audio op-amp, but also proof that “100 MHz or more” is not a universal requirement for a good phono stage
AD797	Extremely low voltage noise; widely used in demanding low-level applications	Powerful choice for very low-noise front ends, but can require careful stability and layout discipline
NE5534 / similar classics	Established low-noise audio workhorse parts	Still useful in many MM applications when the full circuit is designed appropriately

The takeaway is that no single specification—whether gain-bandwidth product, open-loop gain, or input noise voltage—fully predicts performance in a phono stage. Real success comes from matching the active device to the source impedance, gain structure, equalization network, PCB layout, grounding scheme, and overload requirements of the whole design.

8. Building Your Own Phono Preamp

For DIY enthusiasts, building a phono preamp offers both educational value and the possibility of excellent performance. The challenge is that phono stages are unforgiving: they combine high gain, frequency-selective feedback or attenuation, very small signals, and strong sensitivity to grounding and noise.

Power Supply

A clean power supply is essential. Use:

• Regulated supply rails appropriate to the active devices and target headroom
• Thoughtful grounding rather than generic “digital versus analog” separation language if the design is purely analog
• Star grounding or another disciplined return-current strategy to minimize hum loops
• Ample local bypassing near active devices, typically combining small high-frequency capacitors with larger reservoir values

Layout Considerations

• Keep input traces short and shielded wherever practical
• Separate sensitive high-gain nodes from output and power-supply wiring
• Use ground planes judiciously to reduce noise pickup without creating uncontrolled return paths
• Consider shielding or compartmentalization for the input section, especially in high-gain MC stages

Component Quality

Exotic components are not mandatory, but consistency and suitability matter:

• Use precision metal-film resistors for the RIAA network
• Select stable, low-loss capacitors for equalization components
• Match left and right channel parts where channel balance is important
• Verify actual values where practical rather than assuming nominal tolerance tells the whole story

9. Conclusion

The phono preamplifier is a critical component that can make or break vinyl playback quality. Understanding the fundamentals of RIAA equalization, cartridge loading, source impedance, gain distribution, and topology allows you to make better decisions whether you are buying a commercial unit or building your own.

For many listeners, a well-designed MM phono stage offers outstanding performance at reasonable cost. For others, especially those using low-output MC cartridges, the priorities may shift toward lower noise, higher gain, adjustable loading, transformer integration, or more ambitious power-supply design. The best answer is therefore not determined by one slogan, one topology, or one datasheet number, but by how well the complete design serves the cartridge and the rest of the system.

The beauty of vinyl playback lies partly in its analog complexity: every interface matters, from stylus to arm, cable, cartridge, loading network, gain structure, and line stage. Whether you prefer the precision of modern solid-state circuits, the elegance of passive equalization, or the character of a tube-based design, the process of refining the phono stage is part of what makes analog audio so engaging.

Shop Phono Preamplifier

Find More

• Inside the Phono Cartridge: Why MM and MC Use Different Generator Designs — and Often Sound Different
• Learn more about phono stage amplifier
• IWISTAO Discrete Components MM/MC Phono Stage FET Amplifier for LP Phono Split-type AC110V/220V HIFI Audio

References

1. Lipshitz, S. “On RIAA Equalization Networks.” Journal of the Audio Engineering Society, vol. 27, no. 6, 1979. Background discussion and archive links: https://www.andyc.diy-audio-engineering.org/phono-preamp/index.html
2. Hagerman, J. “On Reference RIAA Networks.” http://www.hagtech.com/pdf/riaa.pdf
3. Elliott, R. “RIAA Phono Preamps.” Elliott Sound Products, Project 25. https://www.sound-au.com/project25.htm
4. “Discussion on MC Cartridge Loading.” Extremephono.com. http://www.extremephono.com/Loading.htm
5. “Op-Amp Based RIAA Phono Preamp for MM and MC Phono Cartridges.” DIY Audio Projects. https://diyaudioprojects.com/Chip/Opamp-Phono-Preamp/
6. Millett, P. “LR Phono Preamps.” http://www.pmillett.com/file_downloads/LR%20Phono%20Preamps.pdf
7. Broskie, J. “RIAA Preamps Part 1.” Tube CAD Journal, 2002. https://www.tubecad.com/articles_2002/RIAA_Preamps_Part_1/RIAA_Preamps_Part_1.pdf
8. Audio-Technica VM540ML product page and manual, including recommended load impedance and load capacitance. https://www.audio-technica.com/en-us/vm540ml | https://docs.audio-technica.com/eu/VM540ML_UM_V2_11L_web_161021.pdf
9. Denon DL-103 and DL-103R manuals, including manufacturer loading guidance. https://assets.denon.com/DocumentMaster/DE/Bedienungsanleitung_DL-103.pdf | https://www.denon.com/on/demandware.static/-/Library-Sites-denon_northamerica_shared/default/dwe5f80600/downloads/dl-103r-owners-manual-en.pdf
10. Texas Instruments OPA1656 product page and datasheet. https://www.ti.com/product/OPA1656 | https://www.ti.com/lit/ds/symlink/opa1656.pdf
11. RIAA equalization overview and historical notes, including discussion of the so-called “Neumann pole.” https://en.wikipedia.org/wiki/RIAA_equalization
12. Archive copy of Lipshitz’s discussion of RIAA time constants. https://pearl-hifi.com/06_Lit_Archive/14_Books_Tech_Papers/Lipschitz_Stanley/Lipshitz_on_RIAA_JAES.pdf

Inside the Phono Cartridge: Why MM and MC Use Different Generator Designs — and Often Sound Different

Published by IWISTAO

For many people entering the world of vinyl playback, one question appears almost immediately: if two turntables both play records, why does one cost only a few hundred dollars while another can cost many thousands?

 

Part of the answer lies in the phono cartridge — one of the most important components in the analog playback chain. But it is important to be precise: the cartridge is not the only reason for price differences. Turntable construction, tonearm design, motor and power control, isolation, materials, and manufacturing precision also play major roles. Still, the cartridge is a critical front-end transducer, and its design has a major effect on both system requirements and sonic character.

At its most basic level, a phono cartridge is an electromechanical transducer. The stylus traces the modulations cut into the record groove, and that motion is transferred through the cantilever into the cartridge’s generator system, where it is converted into an electrical signal. That signal is then amplified by the phono stage and the rest of the audio system. Because the cartridge sits at the very beginning of the signal path, it can significantly influence tracking ability, tonal balance, low-level detail retrieval, and the quality of the signal delivered to the downstream electronics.

Today, the two dominant cartridge types are Moving Magnet (MM) and Moving Coil (MC). They are not “two completely different worlds” in an absolute sense, but they are two different generator approaches with different trade-offs in output level, maintenance, system matching, and performance potential.

 

MM Cartridges: The More Accessible and Easier-to-Live-With Option

MM stands for Moving Magnet. In a typical MM cartridge, the stylus travels through the groove and transfers its motion through the cantilever to a small magnet. That magnet moves relative to fixed coils inside the cartridge body, generating the electrical signal. This is the basic operating principle used in many widely available cartridges.

One reason MM cartridges remain so popular is that they are generally easy to integrate into a standard vinyl setup. They usually produce a higher output voltage than MC cartridges and therefore can typically be used directly with a standard MM phono input or MM phono stage. That makes them a practical choice for entry-level and midrange systems.

Another major advantage is maintainability. Many MM cartridges allow the user to replace the stylus assembly separately from the cartridge body. Ortofon, for example, explicitly offers replacement styli for its moving-magnet models and notes that MM cartridges can be serviced by stylus replacement. This often makes long-term ownership simpler and more economical, though the actual replacement cost still depends on the model and brand.

In listening terms, many MM cartridges are often described as full-bodied, forgiving, and musically easy to enjoy. That said, this should not be treated as a hard rule. Sound character varies significantly with cartridge design, stylus profile, cantilever construction, and system matching. Even within one cartridge family, stylus shape alone can influence frequency response, distortion behavior, and subjective tonal balance.

MM cartridges do, however, involve trade-offs. Compared with many well-implemented MC designs, MM cartridges often offer less ultimate headroom in low moving mass and may be less likely to deliver the same level of transient speed, micro-detail recovery, or low-level spatial information in top-tier systems. But this is a matter of tendency, not a universal hierarchy: a strong MM can outperform a mediocre MC, and overall setup quality still matters enormously.

MC Cartridges: Lower Moving Mass and Higher Performance Potential

MC stands for Moving Coil. In an MC cartridge, the relationship is reversed: the coils are attached to the moving cantilever assembly, while the magnet remains fixed inside the cartridge body. As the stylus tracks the groove, the cantilever moves the coils within the magnetic field and generates the signal.

The technical reason MC cartridges are so highly regarded is that the moving coil structure typically has lower moving mass than a moving magnet structure. According to Audio-Technica, this lower mass allows the stylus to react more quickly to changes in the groove, which can result in more detailed reproduction, improved transient response, and wider frequency response. In practice, many listeners associate this with greater clarity, faster attacks, and more revealing retrieval of low-level information.

MC cartridges also tend to demand more from the rest of the system. Because many MC designs produce a much lower output voltage, they often require either a dedicated MC phono input, a dedicated MC phono stage, or a step-up transformer. This is one reason MC systems usually involve greater total cost and more careful matching.

That said, not every MC cartridge is low-output in the same way. High-output MC designs do exist. Cambridge Audio’s Alva MC, for example, is officially specified as a high-output moving coil cartridge with 2mV output and a 47kΩ recommended load, showing that some MC cartridges can be integrated more easily than the traditional low-output type. For that reason, it is not accurate to say that every MC cartridge always requires an external step-up transformer.

Maintenance is another important difference. MC cartridges are typically more delicate than MM cartridges and usually do not have user-replaceable stylus assemblies. When the stylus wears out, the owner often has to replace the cartridge, exchange it through the manufacturer, or send it for specialist retipping. This does not mean every MC is prohibitively expensive, but it usually does mean more complex and potentially higher-cost service compared with a typical MM.

MC cartridges are also more dependent on careful setup and system synergy. Correct tracking force, alignment geometry, anti-skate, arm compatibility, phono gain, and loading all matter. Improper setup can degrade sound quality and, in severe cases, increase wear on both stylus and records. This is not because MC cartridges are inherently dangerous to records, but because higher-performance cartridges tend to reward precision and reveal setup errors more clearly.

The Real Differences Between MM and MC

The most meaningful difference between MM and MC is not brand prestige or marketing language, but design trade-off.

First, MC cartridges usually achieve lower moving mass, which can improve speed of response and the ability to resolve fine groove information. MM cartridges typically move a magnet instead, which often means greater effective moving mass.

Second, MM cartridges usually have higher output and are easier to use with standard phono stages, while many MC cartridges require additional gain and more careful matching.

Third, MM cartridges are often easier to maintain because stylus replacement is commonly available, whereas MC cartridges more often involve whole-cartridge service, exchange, or retipping.

Fourth, the listening differences are best described as tendencies rather than rules. Many MM cartridges are perceived as fuller, smoother, and more forgiving. Many MC cartridges are perceived as faster, more revealing, and more spacious. But these are recurring patterns, not guarantees, and they are heavily influenced by the specific cartridge design and the system around it.

Which One Should You Choose?

An MM cartridge is usually the more sensible choice if you are new to vinyl, want straightforward compatibility, value replaceable styli, or prefer a lower-maintenance and lower-risk ownership experience. That is one reason MM remains such a common and practical recommendation for everyday vinyl listening.

An MC cartridge makes more sense if you already have a suitable phono stage or are willing to invest in one, are comfortable with setup and fine adjustment, and want to pursue the higher performance ceiling that lower moving mass can offer. For many experienced listeners, that extra effort is worthwhile.

For most beginners, starting with a good MM cartridge is the safer and more economical path. But it is not a hard rule that everyone must “graduate” from MM to MC. If the system, budget, and user expectations are aligned, an MC cartridge can also be a valid starting point. The better conclusion is not “MM first, MC later” as an absolute formula, but rather: choose the design that best matches your system, maintenance preferences, and listening priorities.

Final Thought

Vinyl playback is not a simple story of “more expensive is always better.” MM and MC cartridges represent different engineering priorities. MM often offers simplicity, compatibility, and easier upkeep. MC often offers lower moving mass and higher performance potential, but usually at greater cost and with greater demands on setup and system matching. The cartridge may indeed be the “heart” of the front end — but the quality of the result depends on how well that heart works with the rest of the system.

Building your own MM or MC Phono Preamplifier

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References

1. Audio-Technica — What Are the Differences Between Moving Magnet and Moving Coil Phono Cartridges?
2. Audio-Technica — Turntable Cartridges
3. Ortofon — Find the Right Cartridge
4. Ortofon — Replacement Styli
5. Ortofon — Exchange Service
6. Cambridge Audio — Alva MC

IWISTAO Discrete Components MM/MC Phono Stage FET Amplifier for LP Phono

IWISTAO Discrete Components MM/MC Phono Stage FET Amplifier for LP Phono Split-type AC110V/220V HIFI Audio

The phono preamp contains two types of phono amplifiers, MM and MC, which can be adapted to most users' vinyl record players on the market.

Choose fully discrete components to build the circuit, easy to fine-tune the various data parameters.

The main amplifier circuit adopt Field Effect Transistor (FET), which is convenient to reduce the sensitivity of the components to temperature changes and improve the distortion.

Choose pure class A circuit to form discrete component amplifier circuit, effectively reduce harmonic distortion and improve sound effect.

The phono equalization circuit does not use the feedback circuit of the conventional integrated IC circuit, but chooses the attenuation type, whichever is the natural characteristic of the timbre.

The two aluminum chassis are the same size, both are 133mm wide, 63mm high, and 250mm deep.

👇 👇 👇

IWISTAO Discrete Components MM/MC Phono Stage FET Amplifier for LP Phono Split-type AC110V/220V

Learn more about phono stage amplifier

Learn more about phono stage amplifier

Phono amplifier is designed for a phono signal amplification while using Turntables amplifier inside for special sound equalization circuit (RIAA) for restoring vinyl, it cannot be used for other purposes.

Method for checking noise sources

After phono player connected with the phono amplifier stage, if there is a significant low-frequency noise, you need to check in which part of the noise. First unplug the phono amplifier input signal cable to disconnect connection between them, if the low-frequency noise disappeared or significantly reduced, that may explain the noise from the phono player; obvious if the same or reduce low frequency noise , the noise it is very likely to put itself caused by phono amplifier.

It may cause a greater frequency noise that no specialized non-standard phono ground wire.

Generally, nonstandard phonograph is a turntable part of music center to cope with this set of sound designed, when external phono amplifier put to ground that could cause a large hum due to the different ground ways

There is more Phono stage amplifier, and some PCBA Kit. More details, please find the links

Phono stage amplifier

http://www.aliexpress.com/store/group/HIFI-MM-MC-Phono-Amplifier/725205_256242016.html

Phono stage amplifier PCBA Kit

http://www.aliexpress.com/store/group/Amplifier-PCBA-Board-Finished/725205_256211124.html