Information

 RECOMMENDED BIAS SETTINGS

If You Are Using Then Consider Here Is Why It Is The Right Choice
3M 226 3M 966 966 is the perfect choice with lots of benefits
  • is Bias Compatible with 226
  • has same Signal-to-Noise Ratio as 226

has 6 dB less Print Through than 226

  OR  
  3M 996 996 is a step up to a +9dB mastering tape
  • has 3 dB more Headroom than 226
  • has 3 dB greater Signal-to-Noise than 226

has 3 dB less Print Through than 226

3M 806 3M 908 908 is the perfect choice with lots of benefits
  • is Bias Compatible with 806
  • has same +3 dB Max. Oper. Level as 806
  • has same Signal-to-Noise Ratio as 806

has 5 dB less Print Through than 806

  OR  
  3M 966 966 is a step up to a +6 dB mastering tape
  • has 3 dB more Headroom than 806
  • has 3 dB greater Signal-to-Noise than 806

has 3 dB less Print Through than 806

3M 808
(For Nagra)
3M 908 908 is the best Nagra tape ever manufactured
  • performs great without rebiasing
  • has 4 dB less Print Through than 808 BUT with "rebiasing"
  • has 3 dB more Headroom than 808

has 3 dB greater Signal-to Noise than 808

  OR  
  3M 966 966 is the best tape for Stereo Nagra
  • performs great without rebiasing
  • has 1 dB less Print Through than 808 BUT with "rebiasing"
  • has 6 dB more Headroom than 808

has 6 dB greater Signal-to Noise than 808

RECOMMENDED BIAS SETTINGS

MUSIC MASTERING TAPE (Highest Signal-to-Noise)

Tape#

Speed

Record Head Gap 10 kHz Over Bias
 

lps

mils dB

3m996

75

0.125 9
0.25 6.5
0.5 4

15

0.125 6.5
0.25 4
0.5 3

30

0.125 3
0.25 2
0.5 1.5

3M 966

3M 967

3M 250

3M 226

3M 227

75 0.125 7.5
0.25 5
0.5 3.5
15 0.125 5.5
0.25 3
0.5 2.5
30 0.125 2.5
0.25 1.5
0.5 1

GENERAL MASTERING TAPE

Tape#

Speed

Record Head Gap

10 kHz Over Bias

 

lps

mils

dB

3M 806

3M 807

3M 908

75

0.125 6
0.25 4
0.5 3

15

0.125 3
0.25 1.5
0.5 1

30

0.125 1.5
0.25 1
0.5 0.5

 

BIAS SETTINGS Proper bias setting depends on the tape speed and the record head gap length. Smaller or narrower gaps require more over bias as shown in the table.

Record Head Gap Length

Recorder Model Numbers

0.25 mil (6.4 µm)

All models except those listed in the 0.50 mil chart below

0.50 mil (12.7 µm)

Ampex AG440, 1000 (newer models), ATR 100 series, Otari 7800, 5050B(F), MKII-1

OPERATING LEVEL CROSS REFERENCE CHARTS

Maximum Recommended Operating Level ANSI Level DIN Level
3M 966 520 nWb/m (+9 dB) 570 nWb/m (+5 dB)
3M 966/226/250 370 nWb/m (+6 dB) 410 nWb/m (+2 dB)
3M 806/908 250 nWb/m (+3 dB) 280 nWb/m (-1 dB)
3M 808 185 nWb/m ( 0 dB) 200 nWb/m (-4 dB)

Your desired operating level may be different from the reference fluxivity level on your reproduce alignment tape. If this is the case, use the chart above to normalize the operating level to the reference level found on typical reproduce equalization for optimum frequency response using the reproduce alignment tape.

Any combination of signal-to-noise and headroom can be achieved. Using less than the full signal-to-noise capability of the tape (by reducing the operating level) will result in lower distortion, less audible print-through and more headroom.

The reference (fluxivity) level of 320 nWb/m is commonly used in Europe. Due to difference in flux measurement techniques, this is equivalent to approximately 290 nWb/m when measured by American Standard Flux measurement technique as in this chart.

Desired
Operating Level

Reference Fluxivity Level on
Reproduce Alignment Tape

   

ANSI

     

290nWb/m

 

ANSI

DIN

DIN

     

320nWb/m

 
520 nWb/m (+9 dB) 570 nWb/m (+5 dB)

-9 VU

-8 VU

-6 VU

-5 VU

-3VU

 
370 nWb/m (+6 dB) 410 nWb/m (+2 dB)

-6 VU

-5 VU

-3 VU

-2 VU

0VU

 
290 nWb/m (+4 dB) 320 nWb/m (0 dB)

-4 VU

-3 VU

-1 VU

0 VU

+2 VU

 
250 nWb/m (+3 dB) 280 nWb/m (-1 dB)

-3 VU

-2 VU

0 VU

+1 VU

+3 VU

 
200 nWb/m (+1 dB) 220 nWb/m (+3 dB)

-1 VU

0 VU

+2 VU

+3 VU

+5 VU

 
185 nWb/m (0 dB) 200 nWb/m (-4 dB)

0 VU

+1 VU

+3 VU

+4 VU

+6 VU

 

 

PROCEDURE:

Determine the desired operating level.

Determine the reference (fluxivity) level of the reproduce alignment tape you are using.

In the chart, find the VU reading at the point where the values from steps 1 and 2 intersect.

When reproducing the reference level tone from the calibration tape, set reproduce gain so the VU meter reading found in step 3 is achieved.

 

EXAMPLE:

Desired operating level for 3M 806 is 250 nWb/m.

Reference level on alignment tape is 185 nWb/m.

The VU reading is -3 VU at the intersection of the column and row from steps 1 and 2.

Set reproduce gain so VU meter reads -3 VU when reproducing the reference level tone from the calibration tape.