{
  "$schema": "../../data/schema/measurement.schema.json",
  "schema_version": "1.0.0",
  "measurement_id": "GS-2026-0003",
  "record_version": "0.9.2",
  "publication_status": "draft",
  "title": "Audio-Technica AT-OC9XML — Rega P3 / Rega RB330 / Audio Research SP20 — 1 kHz Reference Check",
  "source_report_title": "Rega P3 EVO4 2",
  "slug": "gs-2026-0003-audio-technica-at-oc9xml-rega-p3-rb330-1-khz-reference-check",
  "language": "en",
  "measurement_datetime_local": "2026-09-05T10:01:00",
  "measurement_timezone": "not_recorded",
  "date_published": null,
  "sample_id": "not_recorded",
  "creator": {
    "name": "Michelangelo Canonico",
    "role": "Creator and lead measurer",
    "affiliation": "Direct Sound Records"
  },
  "publisher": {
    "name": "Direct Sound Records",
    "url": "https://directsoundrecords.com/",
    "location_label": "London–Rome"
  },
  "software": {
    "name": "Groove Scope",
    "report_generator_label": "Groove Scope Reference",
    "application_version": "not_recorded",
    "analysis_method_version": "not_recorded",
    "platform": "not_recorded",
    "developer": "Michelangelo Canonico / Direct Sound Records"
  },
  "related_applications": [
    {
      "name": "Resonance Lab",
      "relationship": "Companion application for tonearm and cartridge resonance planning",
      "url": "https://directsoundrecords.com/resonance-lab/"
    }
  ],
  "measurement_type": "1 kHz Reference Check",
  "measurement_scope": [
    "playback speed",
    "rotational stability",
    "DIN-shaped wow and flutter",
    "channel balance",
    "electrical crosstalk",
    "distortion diagnostics",
    "harmonic profile",
    "rotation fingerprints"
  ],
  "setup": {
    "turntable": "Rega P3",
    "tonearm": "Rega RB330",
    "cartridge": "Audio-Technica AT-OC9XML",
    "stylus": "not_recorded",
    "cartridge_hours": "not_recorded",
    "vertical_tracking_force_g": "not_recorded",
    "anti_skate_setting": "not_recorded",
    "alignment_geometry": "not_recorded",
    "azimuth_setting": "not_recorded",
    "vta_or_sra_setting": "not_recorded",
    "phono_stage": "Audio Research SP20",
    "phono_gain_db": "not_recorded",
    "cartridge_loading": "not_recorded",
    "test_record": "not_recorded",
    "test_record_track": "not_recorded",
    "test_record_condition": "not_recorded",
    "nominal_test_tone_hz": 1000,
    "audio_interface_reported_label": "EVO4",
    "audio_interface_full_model": "not_confirmed",
    "interface_gain_settings": "not_recorded",
    "sample_rate_hz": "not_recorded",
    "bit_depth": "not_recorded",
    "capture_device": "not_recorded",
    "channel_routing": "not_recorded",
    "measurement_location": "not_recorded"
  },
  "results": {
    "playback_rpm": {
      "value": 33.34,
      "classification": "primary",
      "condition": "under_stylus_load"
    },
    "playback_speed_error_percent": {
      "value": 0.02,
      "classification": "primary",
      "direction": "fast"
    },
    "settled_rpm": {
      "minimum": 33.26,
      "maximum": 33.42,
      "span": 0.16,
      "classification": "primary"
    },
    "din_shaped_wow_flutter_percent": {
      "value": 0.03,
      "classification": "primary"
    },
    "raw_speed_variation_percent": {
      "rms_plus_minus": 0.144,
      "two_sigma_plus_minus": 0.287,
      "classification": "unweighted_diagnostic"
    },
    "raw_wow_flutter_percent": {
      "wow_rms": 0.14,
      "flutter_rms": 0.033,
      "classification": "unweighted_diagnostic"
    },
    "channel_balance_db": {
      "value": -0.24,
      "classification": "diagnostic_only"
    },
    "crosstalk_1khz_db": {
      "average_separation": 31.8,
      "left_to_right": -30.2,
      "right_to_left": -33.5,
      "directional_difference": 3.27,
      "classification": "supporting_repeat_directional_values"
    },
    "thd_percent": {
      "left": 0.29,
      "right": 0.37,
      "left_minus_right_percentage_points": -0.07,
      "classification": "diagnostic_repeat_before_setup_change"
    },
    "harmonic_profile_db": {
      "h2": {
        "left": -50.8,
        "right": -49.0,
        "left_minus_right": -1.8
      },
      "h3": {
        "left": -68.1,
        "right": -63.3,
        "left_minus_right": -4.8
      },
      "h4": {
        "left": -74.5,
        "right": -67.8,
        "left_minus_right": -6.7
      },
      "h5": {
        "left": -75.2,
        "right": -75.5,
        "left_minus_right": 0.3
      },
      "classification": "diagnostic_repeat_before_setup_change"
    },
    "harmonic_reliability": {
      "classification": "repeat_recommended",
      "quality_note": "The left channel's third harmonic changed most during recording. Repeat before changing the cartridge setup."
    }
  },
  "interpretation": {
    "summary": "The AT-OC9XML achieved 31.8 dB average separation at 1 kHz, 4.8 dB above Audio-Technica's published 27 dB figure, while its measured 0.24 dB channel-balance magnitude sat inside the published 1.0 dB specification. Playback speed was 33.34 RPM (+0.02%) with DIN-shaped wow and flutter RMS of 0.030%.",
    "recommendation": "Use a repeat capture to extend the harmonic comparison and assess whether the left channel's third-harmonic pattern recurs.",
    "repeat_required": true
  },
  "provenance": {
    "source_type": "Groove Scope generated PDF report",
    "source_file": "report.pdf",
    "data_entry_method": "Values transcribed from the source report and independently represented as structured JSON",
    "raw_audio_published": false,
    "raw_audio_note": "No raw test-record audio is included in this record.",
    "sample_ownership": "not_recorded",
    "known_limitations": [
      "The report recommends repetition before changing cartridge setup because the left channel's third harmonic changed most during recording.",
      "The phono-stage gain, cartridge loading, tracking force, anti-skate, test-record edition and track, capture format, application version, and analysis-method version were not recorded in the supplied report.",
      "The sample ID, ownership, measurement location, and timezone were not recorded.",
      "This is a single-session observation."
    ],
    "setup_metadata_source": "Turntable, tonearm, cartridge, Audio Research SP20 preamplifier, and input-interface identification were supplied with the task. Numeric results were transcribed from report.pdf. No absent setup value was inferred from another measurement."
  },
  "files": {
    "human_readable_record": "README.md",
    "source_report": "report.pdf",
    "checksums": "checksums.sha256",
    "source_hero": "assets/source/hero-original.heic",
    "rotation_fingerprints": [
      "assets/source/harmonic-distortion-left.png",
      "assets/source/harmonic-distortion-right.png",
      "assets/source/opposite-channel-leakage-left.png",
      "assets/source/opposite-channel-leakage-right.png",
      "assets/source/level-modulation-left.png",
      "assets/source/level-modulation-right.png",
      "assets/source/speed-deviation-left.png",
      "assets/source/speed-deviation-right.png"
    ]
  },
  "license": "CC-BY-4.0",
  "keywords": [
    "Groove Scope",
    "Direct Sound Records",
    "Michelangelo Canonico",
    "vinyl measurement",
    "turntable speed",
    "wow and flutter",
    "cartridge crosstalk",
    "vinyl distortion",
    "rotation fingerprint",
    "1 kHz reference check",
    "Rega P3",
    "Rega RB330",
    "Audio-Technica AT-OC9XML",
    "Audio Research SP20",
    "EVO4"
  ]
}