Some sounds cannot be digitally replicated. They live in the grooves of vinyl records, the magnetic coating of analog tapes, and the subtle air movement captured by a studio microphone at the moment of performance. The SGL7 exists to deliver these sounds — unaltered, uncolored, and uncompromised — to your listening room.

Design Philosophy: Rebuilding the pure analog experience from the ground up.

Before introducing the SGL7's features, let's discuss the shortcomings of most preamplifiers. The audio industry has long accepted compromises as inevitable: channel imbalance at low volumes, audible switching transients, and power supply noise bleeding into the signal path. These are not quality defects of any particular brand, but inherent limitations of traditional circuit architectures. The SGL7 was developed to break these shackles.

We didn't pile on gimmicky features; instead, we re-examined every fundamental design decision:

· What if volume attenuation didn't rely on wearing mechanical parts?

· What if digital control circuits never touched the analog power supply?

· What if switching sources produced no audible transients?

These questions guided the entire development cycle of the SGL7.

12-Bit R-2R Relay Attenuation System

Conventional carbon-film potentiometers rely on a mechanical wiper sliding across a resistive track. Over time, the wiper wears, and channel tracking drifts, especially at low volumes. This is a structural limitation, not a quality issue. The SGL7 abandons mechanical sliding in favor of precision switching. A 12-bit R-2R resistor network, controlled by sealed relays, provides 4,096 discrete attenuation steps.

Listening experience: Adjusting the volume feels like silk sliding across your fingertips — every step is precisely where it should be.

Dual-Isolated Linear Power Supply

Noise in audio systems is rarely generated by the amplification circuit; it usually comes from power supply pollution, especially when digital and analog circuits share the same power source. The SGL7 uses a fully isolated dual-rail linear power supply.

The two paths are physically separated starting from the transformer secondary winding. High-frequency switching noise from the digital circuit never enters the analog domain.

Measured noise floor: 3 µV.

In a real-world scenario: at 1 AM, with the volume at maximum and your ear against the tweeter, you hear only the silence of the room itself.

POP-Free Operation

The MCU master control system manages all relay timing. Power on/off and input switching strictly follow the correct sequence to eliminate transient signals, protecting your downstream amplifiers and speakers.

Power On: Power amp starts → Delay → Preamplifier output connects

Power Off: Preamplifier output disconnects → Delay → Power amp turns off

Input Switching: Mute → Switch source → Unmute

CNC Precision-Machined Chassis

The SGL7 chassis is not folded sheet metal or welded; it is precision CNC-milled from a solid block of aerospace-grade aluminum.

Monocoque Structure: Seamless, high rigidity, excellent vibration damping.

Multi-Cavity Isolation: Power supply, analog amplification, and control circuits are housed in separate chambers.

430mm Standard Width: Fits most standard racks.

Net Weight: 8 kg: Pick it up, and you'll immediately feel the solid build quality.

Gain adjustment solves the problem of level matching — ensuring sources with different output voltages enter the gain stage at an optimal reference level. Proper gain selection preserves dynamic headroom, reduces clipping, and provides a better SNR for each connected source.

Three Voicing Presets — Shaping the Sound Signature

The three voicing presets are not traditional EQs. They alter the overall sonic character by changing the feedback depth and quiescent bias of the analog amplification circuit.

Neutral Balanced:

Reference-grade transparency, neutral, open, precise imaging, natural transients. Recommended for: Symphonies, chamber music, piano solos, acoustic recordings, and any well-engineered albums. Pairing: Transparent speakers, neutral power amps, high-quality sources.

Warm Vocal:

Rich midrange presence, full-bodied, warm, intimate, highly atmospheric. Recommended for: Vocal pop, jazz, folk, blues, vinyl, remastered vintage recordings. Pairing: Corrects overly bright, thin, or over-analytical systems; excels with tube amps or full-range speakers.

Dynamic Analytical:

Expansive dynamics, sharp and crisp transients, rich layering, and full of tension. Recommended for: Late-Romantic symphonies, film scores, complex rock, concertos, piano sonatas. Pairing: Requires a high-resolution system; amps and speakers must fully track dynamic swings to unleash their full potential.

User-Replaceable Op-Amps — Single/Dual Compatible

Beyond the three factory presets, the SGL7 offers deep tuning space. The internal op-amps are socketed and support both single and dual op-amps.

You can swap them based on your personal preference: choose warm-sounding op-amps for rich tonality, monitoring op-amps for neutrality, or high-speed op-amps for greater dynamics and resolution. Changing one op-amp changes the entire sonic character.

Note: Always disconnect power and take ESD precautions before replacing op-amps. Pay attention to pin orientation. If unfamiliar, please consult a professional.

Combining Gain & Voicing — System Tuning Logic

Gain ensures proper level matching for all sources, preserving headroom and SNR. Voicing adjusts the sound style to suit different music genres.

Quick Setup Reference — Find Your Sound

Technical Note on Voicing

All voicing presets run entirely in the analog domain without using digital DSP. Each step modifies the local feedback depth and quiescent bias of the discrete analog amplification circuit. While bringing perceivable tonal changes, it fully preserves signal integrity and linearity.

The frequency response difference between presets is < 0.5dB. The sonic differences mainly come from harmonic structure, transient response, and spatial presentation, not from altering the frequency curve.

Measured performance remains unchanged in all modes:

THD+N < -116dB @ 1kHz A-wt;

SNR < -126dB @ 1kHz A-wt;

Crosstalk < -140dB @ 10kHz.

Voicing adjustment does not sacrifice hardware specifications; it merely polishes the sonic character.

The SGL7 supports three control methods: front panel buttons, a multi-function encoder knob, and an IR remote control.

Front Panel Buttons : Quick access to input selection, gain, voicing, and mute.

Encoder Knob : Adjusts volume (supports fast rotation). Press to enter parameter mode; cycle through Input, Gain, Mute, Trigger, Brightness, and Voicing. Rotate to select, press to confirm, or wait 3 seconds for auto-confirmation. Long-press for 8 seconds to reset to factory defaults.

Remote Control : Has corresponding shortcut functions.

Auto Standby: Triggers after 90 seconds of mute or inactivity, followed by a 10-second countdown (red LED breathes). Press any key to wake the device.

Display & Parameter Memory

Equipped with a 3.7-inch medical-grade IPS LCD backlit screen.

All five analog input channels can independently save their own volume, gain, and voicing settings. These parameters are retained after power-off; upon restart, the device automatically restores the state from before shutdown without user intervention. Switch sources, and the SGL7 recalls your preferences. Even after power-off, settings remain.

Intelligent Standby

After 90 seconds of mute or inactivity, the machine counts down for 10 seconds and enters low-power standby. The power indicator breathes red in standby; upon waking, it turns solid orange. Press any button on the device or remote to wake it instantly.

Inputs

2x Balanced XLR: For DACs, streamers, CD transports. 3x Single-ended RCA: For phono stages, TVs, game consoles, Bluetooth receivers.

Outputs

2x Balanced XLR: Connect to main power amps, supports bi-amping. 1x Single-ended RCA: Connect to active subwoofer, supports 2.1 channel systems. Perfectly adapts to pure stereo, desktop monitoring, and 2.1 home theater systems.

System Trigger Link (One-Touch Wake)

The SGL7 supports Trigger In/Out daisy-chaining for synchronized power on/off of the entire system: The front-end host powers on and outputs a trigger signal to wake the SGL7, which then forwards the signal to start the power amp.

Rear Panel Core Configuration:

Trigger In/Out: 3.5mm mono jack, supports 5V–12V DC trigger. Ground Binding Post: Unified chassis grounding, reduces ground loop interference. Voltage Selector: Supports 110V/220V mains switching; factory-fitted with dual 1A fuses. IEC Power Inlet: Integrated switch and fuse holder for a clean layout.

SONCOZ has been continuously developing analog audio equipment for years. Through generations of products, we have always adhered to one principle:

Analog circuit design is not just about selecting components. It is about the precise placement of every resistor, the layout of every PCB trace, the planning of every ground loop, and the cumulative impact of all these details on the audio signal path.

The SGL7 is not a product that merely chases paper specifications. It was born for long listening sessions. The state it pursues is when the equipment seems to disappear, leaving only the music flowing.

When you press play and the music gently flows, all the engineering design, instrument testing, and repeated listening tuning ultimately aim to achieve one thing:

faithfully restoring the sound the recording originally intended to convey to you.

"After switching to the SGL7, I realized how much musical detail the previous preamplifier was masking."

— Mr. Zhang, Beijing

"The background is incredibly black; even at maximum volume, I can hardly hear any noise."

— Mr. Li, Shanghai "The differences between the three voicing modes are clearly audible; it's not just audiophile imagination."

— Mr. Chen, Guangzhou (The above is independently collected real user feedback.)