Tape Bias Reference

Reel-to-reel formulation settings at a glance.

Type I

Select a tape

Pick a formulation from the list to see its settings.

Typical bias

—

Depends on machine and tape head.

Equalization

—

Playback time constant.

Reference level

—

Recorded fluxivity at reference.

Machine notes

    Recording guidance

      What to listen for

      Scenarios

      Common setup situations

      Examples of matching tape, machine, and settings for real jobs.

      Archival transfer of old tapes

      You have a box of quarter-inch tapes recorded on unknown machines. Start with Type I settings at 120 microseconds and use a moderate reference level. Leave extra headroom because old recordings often contain unexpected peaks.

      Suggested: any Type I stock, Revox A77 or Studer A80 at 2.5 ips for speech, 7.5 ips for music.

      Recording a loud rock mix

      Use Type II or Type IV stock on a machine with plenty of headroom, like an Otari MX-5050 or Ampex ATR-100. Set bias slightly below the manufacturer's nominal point and use 0 VU at 185 nWb/m for Type II or 250 nWb/m for Type IV.

      Watch for high-frequency saturation on cymbals and snare transients.

      Quiet acoustic session

      This is where over-biasing hurts most. Use a fresh Type II tape and set bias exactly to the machine's calibration. Keep levels steady and avoid long passages near silence. A small amount of noise reduction is often safer than cranking bias to chase tape hiss.

      Suggested: Tascam 38 or Revox A77 with a fresh batch of 468 or SM468.

      Half-inch two-track mastering

      Use Type II or Type IV on a well-aligned half-inch machine. Bias and EQ are the same as quarter-inch, but the wider track gives lower noise and more headroom. Reference level is usually 320 nWb/m for mastering, but check your chain.

      Suggested: Studer A80 or Ampex ATR-100, 15 or 30 ips.

      Local only

      Your saved notes

      Stored in this browser. Nothing leaves your device.

      Watch out

      Common mistakes

      • Using Type II EQ on a Type I tape. It will sound dull and lifeless.
      • Over-biasing quiet recordings to kill hiss. You trade hiss for a flat top end.
      • Ignoring tape age. Old or shedded tape often needs a touch more bias and lower levels.
      • Assuming all Type II tapes sound the same. Batch differences can be surprisingly large.
      • Forgetting to demagnetize heads before calibration. A magnetized head throws off everything.

      Edge cases

      Vintage stocks and odd widths

      Vintage European tapes

      Brands like BASF LH, Agfa PEM 369, and EMI 4026 often sit between modern Type I and Type II. If your machine has adjustable bias, start with Type I EQ and nudge bias up until the top end opens up without getting brittle.

      Ferricobalt (Type III)

      Type III tapes like Sony CS301 were short-lived. They usually want Type II EQ with Type I or Type II bias. Treat them as a specialty stock and bias by ear if you have no manual.

      Two-inch multitrack

      Bias and EQ do not change with width, but track format does. A two-inch 16-track machine often has less headroom per track than a two-track. Keep per-track levels conservative.

      Compact cassette stock on reel

      Some modern reel-to-reel stocks are cassette formulations on wider backing. Treat them as Type II unless the box says otherwise. Keep levels moderate because the thinner base saturates sooner.

      Assumptions

      What this page assumes

      • Your machine is in reasonable mechanical condition with clean heads.
      • You are recording at one of the standard speeds: 3.75, 7.5, 15, or 30 ips.
      • Reference levels are given in nano-webers per meter (nWb/m).
      • You have the machine's manual available for final confirmation.