Up for sale is a custom, mastering-grade 16-Band Stereo Graphic EQ pair in API 500-Series format (2 slots).

Hand-built and calibrated at Altphonic Studio in Tokyo, Japan, this unit was crafted specifically to solve a common limitation in 500-series processors: the lack of ultra-precise, smooth graphic EQs for mastering and bus processing.

■ KEY FEATURES

• STEREO PAIR INCLUDED: Price is for TWO fully built and calibrated 500-series modules.

• SWITCHABLE GAIN RANGE (±3dB / ±6dB / ±12dB): Unlike standard ±12dB graphic EQs (e.g., API 560), the ±3dB mode allows for ultra-smooth 0.1dB-step surgical tone shaping across 16 bands—drawing gentle curves rather than harsh parametric points.

• NO STANDARD KIT PARTS: Built from scratch using premium Japanese audio-grade components (Nichicon audio capacitors, Toshin film caps) for ultra-low noise floor and high signal integrity.

• PERFECT STEREO MATCHING: Fully tested and calibrated using PluginDoctor to ensure identical L/R frequency and phase response.

■ SPECIFICATIONS & SOUND PROFILE

[Select/keep the applicable section below:]

• Op-Amps & Transformers: Floatia Designs custom transformer and op-amp specification.

• Sound Character: Ultra-low noise floor (-140dB level), crystalline transparency, wide dynamic range—ideal for modern high-resolution mastering.

■ TECHNICAL NOTE: ~20Hz BUMP ON PLUGINDOCTOR GRAPHS

If you review the PluginDoctor plots, you may notice a slight bump around 20Hz. Please note that this is purely a known calculation artifact of PluginDoctor’s impulse/FFT measurement method when analyzing transformer outputs with phase shift.

• Real-World Verification: Tested with discrete sine wave sweeps and PPM/VU metering, the actual audio output is 100% FLAT down to 20Hz.

• Designer Confirmation: Verified directly with Joe Malone (JLM Audio designer), who confirmed that this low-end phase artifact is purely cosmetic in PluginDoctor's FFT calculation and does not exist in the real signal.

■ INCLUDED & CONDITION

• Listing includes TWO 500-series EQ modules (Stereo Pair).

• Rack chassis and power supply shown in setup photos are NOT included.

• Fully functional and calibrated, ready for immediate studio operation.

■ SHIPPING & PAYMENT

• Fast, insured worldwide shipping via EMS from Tokyo, Japan.

• Tracked shipment with secure, professional packaging.

Please feel free to send a message if you have any questions or require further technical details!