Behringer 1273 Dual Microphone Preamplifier + 3-Band EQ

{
  "schema_version": "capability-outboard-v1",
  "id": "behringer1273",
  "name": "Behringer 1273 Dual Microphone Preamplifier + 3-Band EQ",
  "maker": "Behringer (Music Tribe)",
  "clone_of": "Neve 1073",
  "clone_of_note": "Manual p.5: 'The 1273 draws inspiration from the classic Neve modules from the 1970s, regarded by many as the best microphone preamp available'. Manual p.7 (Feature list): 'Two-channel microphone preamplifier with 3-band equalizers, based on the classic 1073 design'. The 1273 is Behringer's 2-channel rackmount realisation of the 1073 channel-strip topology (preamp + 3-band inductor EQ + HPF) using Class A discrete circuitry and custom Midas input/output transformers.",
  "device_class": "preamp",
  "device_class_subtypes": [
    "preamp",
    "eq"
  ],
  "device_class_subtypes_note": "Behringer's marketing positioning is '2 Channel Microphone Preamplifier' with EQ listed as a feature (manual p.3 Specifications). Primary class = preamp per the capability-outboard-v1 §C rule (marketing positioning over functional union). The EQ subtype is independently engageable via the panel EQ IN switch; HPF stays active when EQ is bypassed (manual p.14).",
  "topology": "discrete-Class-A, transformer-coupled, inductor-based EQ",
  "topology_note": "Manual p.7 Feature list: 'Class A, all discrete circuitry for highest signal integrity', 'Custom-built Midas input and output transformers', 'Inductor-based switchable equalizers section with a passive third-order high-pass filter'. The 5-position HPF is inductor-based per p.7. Preamp gain stage uses 'Electronically controlled resistor-stepped 80 dB rotary gain switch' for precision.",
  "channels": 2,
  "linkable": false,
  "linkable_note": "Two independent channels, no stereo-link/couple switch (manual p.11-12 controls list; +48V is 'switched independently per channel', p.14). The unit is dual-mono, not a stereo-linkable pair.",
  "params": {
    "preamp": {
      "gain_range_db": "-20..+80",
      "gain_range_db_note": "Manual p.12: 'The preamp has a gain range of -20 dB to 80 dB in 5 dB steps' via the resistor-stepped rotary gain switch.",
      "phantom_48v": true,
      "phantom_48v_note": "Manual p.11: '+48 V – Push to apply +48 V phantom power to the front and rear XLR inputs'. Switched independently per channel (p.14).",
      "pad_db": null,
      "pad_db_note": "No dedicated input pad. Gain attenuation below 0 dB is achieved via the -20..0 dB low end of the 5 dB stepped gain switch (manual p.12).",
      "polarity_invert": true,
      "polarity_invert_note": "Manual p.11: 'Ø – Polarity 180° invert button'. Per channel.",
      "hpf_hz": null,
      "hpf_hz_note": "The 1273 HPF is a 5-position selector (OFF / 50 / 80 / 160 / 300 Hz) per manual p.7 Feature list + p.12 control 14. The single-int `hpf_hz` field doesn't fit multi-position selectable HPFs; the corner set is recorded in `hpf_corners_hz` (additive field landed first-use, see provenance.verify_note). The HPF is inductor-based and stays active when EQ is switched out of circuit (manual p.14).",
      "hpf_corners_hz": [
        50,
        80,
        160,
        300
      ],
      "hpf_corners_hz_note": "Additive field landing first-use per capability-outboard-v1 §D additive rule. The 1273 (and several other rackmount preamps in the catalog) expose HPF as a multi-position selector, not a single fixed corner. The array carries the enabled corners in ascending order; the OFF position is implicit (any selectable HPF has an OFF detent).",
      "inst_input": true,
      "inst_input_note": "Manual p.11 control 8: 'INST – Activates the front panel instrument input. This button disables the other 2 inputs (Mic/Line).' Manual p.10: 'Instrument input 600 kΩ'. Front-panel 1/4\" TS jack per channel.",
      "transformer_coupled": true,
      "transformer_coupled_note": "Manual p.7 Feature: 'Custom-built Midas input and output transformers'. Per-channel transformer-balanced in + transformer-balanced out. The TONE switch (manual p.11 control 5) toggles the input transformer impedance between 1200 Ω (out) and 300 Ω (in)."
    },
    "eq": {
      "bands": [
        {
          "kind": "low_shelf",
          "freq_hz": "35..220",
          "freq_hz_steps": [
            35,
            60,
            110,
            220
          ],
          "gain_db": "-15..+15",
          "q": null,
          "_note": "Manual p.7 + p.12 control 11: 'low band has ±15 dB gain ... selects the frequency: off, 35 Hz to 220 Hz in 5 steps' (OFF + 4 corners). Stepped frequency selector via inner concentric control. Inductor-based proportional-Q shelf (Q fixed by topology; not user-adjustable). Manual p.14 confirms the LOW band is a shelf: 'Low Shelf function (cut or boost all frequencies the same adjustable amount below the selected frequency)'."
        },
        {
          "kind": "peak_bell",
          "freq_hz": "360..7200",
          "freq_hz_steps": [
            360,
            700,
            1600,
            3200,
            4800,
            7200
          ],
          "gain_db": "-15..+15",
          "q": null,
          "_note": "Manual p.7 + p.12 control 12: 'mid band has ±15 dB gain ... selects the frequency: off, 360 Hz to 7.2 kHz in 7 steps' (OFF + 6 corners). Manual p.14: 'Mid Cut/Boost which applies a bell curve cut or boost at the selected frequency'. Inductor-based proportional-Q peak (Q varies with gain by the inductor topology; not user-adjustable)."
        },
        {
          "kind": "high_shelf",
          "freq_hz": "10000..16000",
          "freq_hz_steps": [
            10000,
            12000,
            16000
          ],
          "gain_db": "-15..+15",
          "q": null,
          "_note": "Manual p.7 + p.12 control 13: 'high band has ±15 dB gain ... selects the frequency: off, 10 kHz to 16 kHz in 4 steps' (OFF + 3 corners). Manual p.14: 'High Shelf function (cut or boost all frequencies the same adjustable amount above the selected frequency)'. Inductor-based proportional-Q shelf."
        }
      ],
      "bands_note": "The HPF is documented under params.preamp (hpf_corners_hz) not in the EQ bands array, because the 1273's HPF stays active when EQ IN is switched off (manual p.14: 'The HI-PASS can be used to remove excess rumble from the signal if required and is still active if the EQ is switched out of circuit'). Treating it as a preamp-section filter matches signal-flow reality. The eq.bands[] entries each represent stepped-frequency-selector bands; the `freq_hz_steps[]` per-band additive field carries the actual selectable corners (additive sibling to the schema's `freq_hz` range string).",
      "eq_bypass": true,
      "eq_bypass_note": "Manual p.12 control 15: 'EQ IN – Switch the EQ in and out of circuit. The LED indicates the EQ circuit is active.' Per-channel EQ bypass switch."
    }
  },
  "io": {
    "audio_in": {
      "format": [
        "combo_xlr_trs",
        "xlr",
        "trs",
        "ts"
      ],
      "balanced": true,
      "impedance_ohms": null,
      "impedance_ohms_note": "The 1273's input impedance varies by source type and TONE switch position (manual p.10): mic 300 Ω (TONE in) / 1200 Ω (TONE out), line 10 kΩ, instrument 600 kΩ. The single int field doesn't fit this multi-mode impedance; the values are documented here. Mic-impedance switching is via the front-panel TONE button (manual p.11 control 5).",
      "inst_zi": true,
      "inst_zi_note": "Manual p.11 control 8/9: front-panel 1/4\" TS instrument input, 600 kΩ input impedance (manual p.10). The input transformer is in the instrument path so the TONE switch warms instruments too (manual p.14)."
    },
    "audio_out": {
      "format": [
        "xlr",
        "trs"
      ],
      "balanced": true,
      "impedance_ohms": 80,
      "impedance_ohms_note": "Manual p.10: 'Line Output – Transformer Balanced XLR and 1/4\" TRS connectors – <80 Ω'. The schema's int field records the upper bound (80); the '<' qualifier is in the note."
    },
    "sidechain": {
      "send": false,
      "return": false,
      "format": null,
      "per_channel": false,
      "_note": "The 1273 has no compressor and therefore no sidechain. It DOES have a per-channel INSERT (post-gain, pre-EQ) on rear-panel 1/4\" TS SEND + RETURN (manual p.13 controls 22/23 + p.14: 'The unbalanced insert point allows other external equipment to be placed in the signal chain before the EQ such as a compressor'). The insert is a signal-path insert (for splicing in external processing), not a compressor sidechain, and is documented via the panel.json REAR_IO section + the CH<n>_INPUT INSERT toggle. Not modeled in io.sidechain to preserve the sidechain block's semantic (compressor sidechain only)."
    },
    "stereo_link": false,
    "bypass": "none",
    "bypass_note": "No global processing bypass. The EQ IN switch (per channel, manual p.12 control 15) bypasses the EQ section only; signal still passes through preamp + transformer + insert + HPF (HPF stays active per p.14). Recorded as 'none' because the schema's bypass field refers to a unit-level bypass mechanism.",
    "operating_level": [
      "+4dBu"
    ],
    "operating_level_note": "Manual doesn't expose a +4 dBu / -10 dBV switch; the 1273 operates at professional +4 dBu line level per the transformer-balanced I/O design. Manual p.12 control 16: 'To achieve the full gain as indicated on the gain switch, level has to be set to full (0 dBu in, 0 dBu out for 0 dB on gain switch setting)' implies the unit's nominal reference.",
    "rack_format": "2U",
    "rack_format_note": "Manual p.7 Feature list: 'Rugged 2U rack mount chassis for durability in portable applications'."
  },
  "meters": [
    {
      "kind": "peak",
      "stages": 7,
      "range_db": "-30..+24",
      "shared": false,
      "_note": "Manual p.7 + p.12 control 17: 'High-precision 7-segment LED signal level meter for each channel ... METER – Shows output level from -30 dB to 24 dB'. The manual doesn't specify the detector (peak vs PPM); 7-segment LED ladders on this class of preamp are typically peak-reading. Per-channel (shared=false)."
    }
  ],
  "performance": {
    "bypass_per_channel": false,
    "auto_release": false
  },
  "provenance": {
    "manual_path": "manuals/preamp-outboard--behringer-1273-manual.pdf",
    "confidence": "high",
    "last_verified": "2026-05-27",
    "manual_pages": [
      3,
      5,
      6,
      7,
      10,
      11,
      12,
      13,
      14
    ],
    "verify_via": "SM46 single-seat manual extraction. P8 rack-tier completion (4-device cluster).",
    "verify_note": "Manual-grounded extraction from manuals/preamp-outboard--behringer-1273-manual.pdf. Class A discrete, transformer-coupled (Midas), 2-channel mic preamp + 3-band inductor EQ + 5-position inductor HPF. Two new additive fields land first-use per capability-outboard-v1 §D additive rule: (1) `params.preamp.hpf_corners_hz: int[] | null` records the corner set of a multi-position selectable HPF when the single-int `hpf_hz` doesn't fit (1273, and anticipated for other multi-position-HPF rackmount preamps); (2) `params.eq.bands[].freq_hz_steps: int[]` records the discrete selectable corner steps when an EQ band's frequency control is a stepped selector rather than a continuous sweep (1273's stepped-frequency low/mid/high bands). Both fields are sibling to existing string-range fields (`hpf_hz`, `freq_hz`) and are additive only (existing readers ignore unknown fields). EQ bands modeled with q=null because inductor-based proportional-Q topology fixes Q at the design layer (not user-adjustable). Insert send/return (rear-panel TS, per channel) is NOT modeled in io.sidechain to preserve sidechain's compressor-only semantic; documented via panel.json INSERT toggle + REAR_IO section.",
    "fields": {
      "device_class": {
        "conf": "high",
        "pg": 3
      },
      "device_class_subtypes": {
        "conf": "high",
        "pg": 7
      },
      "clone_of": {
        "conf": "high",
        "pg": 5
      },
      "topology": {
        "conf": "high",
        "pg": 7
      },
      "channels": {
        "conf": "high",
        "pg": 3
      },
      "linkable": {
        "conf": "high",
        "pg": 11
      },
      "params.preamp.gain_range_db": {
        "conf": "high",
        "pg": 12
      },
      "params.preamp.phantom_48v": {
        "conf": "high",
        "pg": 11
      },
      "params.preamp.polarity_invert": {
        "conf": "high",
        "pg": 11
      },
      "params.preamp.hpf_corners_hz": {
        "conf": "high",
        "pg": 7
      },
      "params.preamp.inst_input": {
        "conf": "high",
        "pg": 11
      },
      "params.preamp.transformer_coupled": {
        "conf": "high",
        "pg": 7
      },
      "params.eq.bands.0.kind": {
        "conf": "high",
        "pg": 14
      },
      "params.eq.bands.0.freq_hz_steps": {
        "conf": "high",
        "pg": 7
      },
      "params.eq.bands.0.gain_db": {
        "conf": "high",
        "pg": 12
      },
      "params.eq.bands.1.kind": {
        "conf": "high",
        "pg": 14
      },
      "params.eq.bands.1.freq_hz_steps": {
        "conf": "high",
        "pg": 7
      },
      "params.eq.bands.1.gain_db": {
        "conf": "high",
        "pg": 12
      },
      "params.eq.bands.2.kind": {
        "conf": "high",
        "pg": 14
      },
      "params.eq.bands.2.freq_hz_steps": {
        "conf": "high",
        "pg": 7
      },
      "params.eq.bands.2.gain_db": {
        "conf": "high",
        "pg": 12
      },
      "io.audio_in.format": {
        "conf": "high",
        "pg": 11
      },
      "io.audio_in.inst_zi": {
        "conf": "high",
        "pg": 10
      },
      "io.audio_out.format": {
        "conf": "high",
        "pg": 13
      },
      "io.audio_out.impedance_ohms": {
        "conf": "high",
        "pg": 10
      },
      "io.bypass": {
        "conf": "high",
        "pg": 12
      },
      "io.operating_level": {
        "conf": "medium",
        "pg": 12
      },
      "io.rack_format": {
        "conf": "high",
        "pg": 7
      },
      "meters.0.stages": {
        "conf": "high",
        "pg": 7
      },
      "meters.0.range_db": {
        "conf": "high",
        "pg": 12
      },
      "meters.0.kind": {
        "conf": "medium",
        "pg": null
      }
    }
  }
}