1. Calibration:
    1. Preparations:
      1. Check interface is in 96kHz mode and all processing/effects are off
      2. Check/select interface in the APP and activate WASAPI/AuHAL if available and reliable
      3. Check app "Input Level" and "Osc Output" pots are in "Cal." positions
      4. Connect device to interface. Use CD Direct inputs if available. Use Fixed level outputs if available
    2. Levels calibration
      1. Device REC/Input level and Output level pots to 75% position (3 o'clock)
        1. or to CAL position if known (Fixed level outputs if available should be considered CAL output)
      2. Switch device to SOURCE position (or put it to REC PAUSE if 2 head)
      3. APP Function to "Level"
      4. APP "Input level" to 0dB
      5. OSC to 400hz
      6. Adjust interface output to read 0db on device meter
      7. Adjust interface input so APP meter reads 0db on "Level" scale
      8. Check above two steps do not result in OS software volume pots in positions below 50% of the scale
      9. Check syne on the app scope for clipping. Use "Level -20dB" on Function, plus -20dB on "Scope" page "Osc. Output Level" if needed
    3. Interface FR calibration (if changed)
      1. Connect loopback cable output to input of the interface
      2. Adjust app "Level" display to read 0db
      3. Select "Sound Card FR Compensation" option in "NAK T-100" menu, click START
      4. Click "Save as Default"
      5. Click OK
    4. Voltage calibration (if absolute voltage readout is needed)
      1. Connect the attenuator or activate the PAD on input
        1. NOTE: PAD is usually -20db which corresponds to app "Input Level" position +20dB / 10V
      2. See "Voltage Calibration" in manual

  2. Device adjustments and checks:
    1. NOTE:  Tape machines adjustments / calibration is not a simple task. It require full understanding of the process, understanding of your tools, and in most if not all cases, reading and understanding the service manual and manufacturers procedures. This is a CHECKLIST to follow, if you satisfy this criteria. Otherwise, it is STRONGLY recommended to perform only "Preparation" section, skip any adjustments that cannot be easily reverted, and proceed with the Measurements section below.
    2. Preparation
      1. Make sure transport is clean and pots/switches on device are not noisy
      2. DEMAGNETISE TAPE PATH! Seriously!
      3. Turn off NR, MPX, auto rec level and everything else that alters input/output signal.
      4. On device, Select correct tape type you will use in it
      5. If the deck has auto CAL, perform it
        1. If auto CAL procedure includes REC level, repeat Level Calibration with new settings set by the auto CAL procedure
    3. BIAS / EQ adjust / REC level (if device has no auto cal, but has EXTERNAL manual controls)
      1. (NOTE: all devices have BIAS/EQ trimmers inside, so this effort may be best left for the servicing stage)
      2. Switch to "Scope" mode
      3. Select "FR Pink"
      4. Select "0dB" on "Osc. Output Level" toggle switch
      5. Start REC
      6. Adjust BIAS pot to obtain subjectively flattest high frequency response on the app display
      7. Adjust REC EQ if available as per device manual
      8. DO NOT manually adjust REC LEVEL even if available! (we already did Level Cal)
      9. Switch to Basic mode, turn Function dial to "T.H.Dist." mode
      10. Check that distortion readings are less then 1% on both channels
        1. As needed go back and forth between Frequency, EQ and Distortion to achieve optimal balance between them
      11. Write down results
    4. Azimuth adjust/check (highly recommended, if device has externally accessible Azimuth adjust controls)
      1. NOTE 1. This test cannot be self-referenced. Be aware that if you are not using CAL tapes and manufacturers procedures, IT IS RECOMENDED TO SKIP THIS ADJUSTMENT. Once you start fiddling with azimuth, there is no easy way to revert to previous state. It is of course perfectly safe to just use this step as a measurement to check azimuth, without changing anything.
      2. NOTE 2: all devices have Azimuth adjust screws inside, so this effort may be best left for servicing stage
      3. Start playing azimuth CAL tape
      4. In "Basic" mode, turn Function dial to "Level" position
      5. Adjust azimuth to reach maximum level possible
      6. Switch to "Scope" mode, select "O'scope"
      7. Fine-tune azimuth to align the two sine waves in phase
      8. Optionally select "Lissajous"
      9. Adjust azimuth to obtain a scope redout ellipse as close to the 45 degree line as possible
      10. Write down results
  3. Measurements:
    1. Speed
      2. Function dial to "Speed  Wow/Flutter" position
      3. Select "Speed Cal." frequency depending on CAL tape (next to "Speed Cal." Position)
      4. Switch device Monitor to "Tape" position
      5. Play SPEED CAL tape (obtained from the reputable source)
      6. Read "Speed" on meter
      7. Write it down
    2. Wow/Flutter:
      1. Function dial to "Speed Wow/Flutter" position,
      2. Select "Speed Cal." frequency depending on CAL tape (next to "Speed Cal." Position)
      3. Switch device Monitor to "Tape" position
      4. Play SPEED CAL tape (obtained from the reputable source)
        1. Alternatively, insert blank tape and start REC
      5. Read the "Wow/Flutter" meter
      6. If needed, use the "Meter Range" switch to adjust sensitivity
      7. If needed, switch between Q-PK (default) and WRMS (next to "Speed" position)
      8. If needed, switch to "Advanced" display mode for logging and W&F frequency domain display
      9. Write down results
    3. THD
      1. Function dial to "T.H.Dist." position
      2. Switch device Monitor to "Tape" position
      3. Start recording
      4. Switch between L and R channels and read the meter "T.H.Dist." scale (same scale/meter for both L and R)
      5. Use the label to switch between 400 and 1000 Hz as desired
      6. Write down results
    4. S/N ratio
      1. Function dial to "Noise-A (-40db)" position
      2. Switch device Monitor to "Tape" position
      3. Start recording
      4. Read the L & R meter on "dB" scale and deduct 40 from the readout
      5. If "Meter Range" switch is at -20dB/0.1% position, deduct another 20
      6. Turn on noise reduction and read again
      7. Write down results
    5. Frequency response
      1. Switch to "Scope" mode
      2. Switch device Monitor to "Tape" position
      3. Select "FR Pink" on the right hand side (similar conditions to normal listening)
      4. Start recording
      5. Select "FR White" for standard specification measurement and set to -20dB
      6. For precise results switch to "FR Sweep"
      7. Take measurements for 0dB and -20dB levels, pin results for each level
      8. Take screenshot and/or record results for +-3db range (Columns R and S)
For recording results with convenience, consider downloading this free spreadsheet template.