Tone Controls
IEC or NAB. 7.5 or 30 IPS. Bias - Forward or Back.
The IEC/NAB switch selects the playback EQ curve. IEC brings more top-end clarity and a slightly leaner low end - the European standard, brighter and more present. NAB gives more low-end weight and warmth, the classic American tape character that most engineers think of when they think of tape. The switch is active in all three modes. Tape speed changes the frequency response shelving: 7.5 IPS adds LF weight and softens the HF, giving a thicker, darker character with slightly more saturation feel. 15 IPS is baseline. 30 IPS lifts the HF and trims a touch of low end, giving a faster and more open character with less apparent saturation. The BIAS knob adjusts the harmonic ratio and HF response across a trim range above and below nominal. Turn it counter-clockwise for under-biased character: HF is lifted, more third-harmonic content, brighter and more aggressive. Turn it clockwise for over-biased: HF softens, more second-harmonic warmth, the rolled-off sound of tape pushed past optimal. The HF TRIM knob is a final shelving low-pass, independent of everything else - dial it down to taste when the top end is right and you just want a touch more air rolled off.
- IEC - European playback curve. More top-end clarity, leaner low end
- NAB - American playback curve. More low-end weight and warmth
- 7.5 IPS - +2-3 dB LF shelf ~80 Hz, -4 dB HF shelf ~9 kHz, darker and thicker
- 15 IPS - Neutral baseline
- 30 IPS - -1.5 dB LF shelf ~80 Hz, +2 dB HF shelf ~13 kHz, brighter and more open
- BIAS - Under/over bias trim. Counter-clockwise = brighter, more aggressive. Clockwise = warmer, rolled off
- HF TRIM - Final shelving low-pass, independent of bias and tape speed