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Product Archive

FAS406A

Companion 3-way electronic crossover documented alongside Son of Frank Amp'n Stein (FAS-2400).

Category

Equalizer / Processor / Crossover

Series

Special Series (MS/M Based)

Era

1990s companion component (archived FAQ source)

FAS406A family-layout reference
Layout reference image for the AX/FAS 406A crossover family. FAS406A units may use different cosmetic colorways.

Specifications

Crossover Slope
18dB per octave
Crossover Frequency Method
R-Net programmable resistor network
Signal to Noise Ratio (A-Weighted)
100dB
Output Voltage Level
8V
Dimensions
9.5"L x 5.75"W x 1.3"H

Visual Identification Notes

  • Referenced as the matching crossover for FAS-2400 in archived FAQ material.
  • Archive documentation should include panel labels and R-Net socket details when available.
  • Community verification indicates FAS406A is functionally aligned with AX-406A layout but can appear in different period color/finish variants.
  • Capture connector orientation before any bench rewiring or recap work.

Known Issues

  • R-Net programming details are often missing from second-hand units.
  • Internal service history is frequently undocumented in collector listings.

Recommended Service Actions

  • Verify R-Net resistor values and intended crossover targets before power-up.
  • Inspect all connectors and controls for oxidation or intermittent behavior.
  • Record measured noise floor and channel balance after service.

Parts List

  • Dual op-amp for preamp / crossover stage

    Original: Legacy dual DIP-8 op-amp (marking varies by production run)

    Replacement: Low-noise audio op-amp DIP-8

    Verification: Proposed

DigiKey Recommendations

  • Audio-grade dual op-amp replacement

    DigiKey: P23456-ND

    Placeholder DigiKey reference. Verify stability and compensation in original circuit before bulk install.

    Open DigiKey reference

Gallery

FAS406A family-layout reference

FAS406A family-layout reference

Layout reference image for the AX/FAS 406A crossover family. FAS406A units may use different cosmetic colorways.

Historical Notes

  • MS Special Page Cross-Checks

    Multiple special-platform values on the MS Special page overlap with MS/MPS baseline tables (notably MQ430 and MS2125 sections), while some values such as MS275 bridged output differ and remain flagged for revision check.

Source-Backed Verification

  • FAS and SoFAS limited-series context

    Cross-checked
    • Frank Amp'n Stein (FAS2300) is described as MQ430 + MS2125 in one heatsink with an approximately 300-unit limited run note.
    • Son of Frank Amp'n Stein (FAS2400) is described as a MS275 + MS2125 4-3-2 special platform with matching FAS406A crossover references.
    • MS1000 is described as two MS2250 sections integrated in one long heatsink with high thermal/current demand cautions.
    • FAS406A companion crossover values include 18dB/oct slope, 8V output level, and 100dB S/N in the same archived source.

    Source: Archived Phoenix Gold FAQ - MS Special Edition

    Open source page

  • LPL44 and R-Net accessory guidance

    Imported - Needs Primary Verification
    • LPL44 is described as a remote bass level control that works when low-pass crossover mode is active.
    • RJ11 repair guidance lists left = black, center = red+green, right = yellow at the LPL44 solder points.
    • The archived formula for crossover R-Nets is resistor value (kohms) = 18,800 / target crossover frequency (Hz).

    Source: Archived Phoenix Gold FAQ - Accessories

    Open source page

  • AX-406A resistor-network crossover programming

    Cross-checked
    • AX-406A documentation uses resistor-network programming to set crossover frequency values.
    • Archived Accessories FAQ repeats the same calculation model: 18,800 / desired frequency (Hz) = resistor value (kohms).
    • Both sources emphasize careful resistor-value selection to avoid frequency target drift.

    Source: AX406A Manual (archive PDF)

    Open source page

Sources / Notes

  • Archived Phoenix Gold FAQ - MS Special Edition

    Primary source for FAS406A spec table values and companion-model context.

    Open source

  • Community model-color note

    FAS406A reported as AX-406A family-equivalent with alternate finish/color variants in period builds.

Model Disclaimer Block

Repair information is provided at user's own risk. Verify all measurements and polarity before power-up.

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