Untitled Document

This checklist is intended as a step-by-step procedures REMINDER for an at least somewhat knowledgeable user, to ensure CONSISTENCY of measurements and adjustments. It is NOT A CHEAT-SHEET! Understanding at least basics of magnetic tape recording, NAK T-100 application and capabilities and function of your device IS A PREREQUISITE for using this checklist.

NOTE #1: This checklist is NOT A REPLACEMENT FOR THE NAK T-100 MANUAL! If in doubt, read the corresponding section of the manual. IT IS HIGHLY RECOMMENDED TO READ THE NAK T-100 MANUAL FULLY AT LEAST ONCE BEFORE USING THIS CHECKLIST - as well as the service manual for your device!

NOTE #2: This checklist is currently written to be used without changes for 3-head devices. For devices not capable of simultaneous REC/PLAY , REC-rewind-PLAY cycle should be used instead wherever the checklists refers to "start recording"

NOTE #3: Some tests CANNOT be self-referenced and require a test tape (CAL tape) as a point of reference (such as the speed test). Some tests can be completed without reference, but in that case be aware that you are measuring recording AND playback at the same time (for example FR). In that situation, it will be hard to tell if the measurement is limited by REC or PLAY function of your device. Therefore, it is highly recommended to use a CAL tapes from a reputable source to establish a reference. Adjust the steps below accordingly. The list is written to provide MINIMUM VIABLE measurements without using CAL tapes where possible. And be aware that "possible" does not equal "ideal" or "completely accurate"

Device: Device under test (eg. tape recorder)
Interface: Audio interface (soundcard)
APP: The "NAK T-100" application
OS: Operating system (eg. Windows or macOS)
Function: large round rotary switch on the LEFT hand side of the app in Basic mode)
OSC: Oscillator (large round rotary switch on the RIGHT hand side of the app in Basic mode)
Scope: Oscilloscope (the "O'scope" function and display, in "Scope" mode of the app)
Pot: Potentiometer (software or hardware)
CAL: Calibrated/Calibration
FR: Frequency Response
Text in ORANGE: clickable orange labels in the app that toggle values and settings
Text in "quotes" refers to the text labels in the APP

Calibration:

Preparations:

Check interface is in 96kHz mode and all processing/effects are off
Check/select interface in the APP and activate WASAPI/AuHAL if available and reliable
Check app "Input Level" and "Osc Output" pots are in "Cal." positions
Connect device to interface. Use CD Direct inputs if available. Use Fixed level outputs if available

Levels calibration

Device REC/Input level and Output level pots to 75% position (3 o'clock)

or to CAL position if known (Fixed level outputs if available should be considered CAL output)

Switch device to SOURCE position (or put it to REC PAUSE if 2 head)
APP Function to "Level"
APP "Input level" to 0dB
OSC to 400hz
Adjust interface output to read 0db on device meter
Adjust interface input so APP meter reads 0db on "Level" scale
Check above two steps do not result in OS software volume pots in positions below 50% of the scale
Check syne on the app scope for clipping. Use "Level -20dB" on Function, plus -20dB on "Scope" page "Osc. Output Level" if needed

Interface FR calibration (if changed)

Connect loopback cable output to input of the interface
Adjust app "Level" display to read 0db
Select "Sound Card FR Compensation" option in "NAK T-100" menu, click START
Click "Save as Default"
Click OK

Voltage calibration (if absolute voltage readout is needed)

Connect the attenuator or activate the PAD on input

NOTE: PAD is usually -20db which corresponds to app "Input Level" position +20dB / 10V

See "Voltage Calibration" in manual

Device adjustments and checks:

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.
Preparation

Make sure transport is clean and pots/switches on device are not noisy
DEMAGNETISE TAPE PATH! Seriously!
Turn off NR, MPX, auto rec level and everything else that alters input/output signal.
On device, Select correct tape type you will use in it
If the deck has auto CAL, perform it

If auto CAL procedure includes REC level, repeat Level Calibration with new settings set by the auto CAL procedure

BIAS / EQ adjust / REC level (if device has no auto cal, but has EXTERNAL manual controls)

(NOTE: all devices have BIAS/EQ trimmers inside, so this effort may be best left for the servicing stage)
Switch to "Scope" mode
Select "FR Pink"
Select "0dB" on "Osc. Output Level" toggle switch
Start REC
Adjust BIAS pot to obtain subjectively flattest high frequency response on the app display
Adjust REC EQ if available as per device manual
DO NOT manually adjust REC LEVEL even if available! (we already did Level Cal)
Switch to Basic mode, turn Function dial to "T.H.Dist." mode
Check that distortion readings are less then 1% on both channels

As needed go back and forth between Frequency, EQ and Distortion to achieve optimal balance between them

Write down results

Azimuth adjust/check (highly recommended, if device has externally accessible Azimuth adjust controls)

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.
NOTE 2: all devices have Azimuth adjust screws inside, so this effort may be best left for servicing stage
Start playing azimuth CAL tape
In "Basic" mode, turn Function dial to "Level" position
Adjust azimuth to reach maximum level possible
Switch to "Scope" mode, select "O'scope"
Fine-tune azimuth to align the two sine waves in phase
Optionally select "Lissajous"
Adjust azimuth to obtain a scope redout ellipse as close to the 45 degree line as possible
Write down results

Measurements:

Speed

SKIP THIS TEST IF YOU HAVE NO CAL TAPE FOR SPEED!
Function dial to "Speed Wow/Flutter" position
Select "Speed Cal." frequency depending on CAL tape (next to "Speed Cal." Position)
Switch device Monitor to "Tape" position
Play SPEED CAL tape (obtained from the reputable source)
Read "Speed" on meter
Write it down

Wow/Flutter:

Function dial to "Speed Wow/Flutter" position,
Select "Speed Cal." frequency depending on CAL tape (next to "Speed Cal." Position)
Switch device Monitor to "Tape" position
Play SPEED CAL tape (obtained from the reputable source)

Alternatively, insert blank tape and start REC

Read the "Wow/Flutter" meter
If needed, use the "Meter Range" switch to adjust sensitivity
If needed, switch between Q-PK (default) and WRMS (next to "Speed" position)
If needed, switch to "Advanced" display mode for logging and W&F frequency domain display
Write down results

Function dial to "T.H.Dist." position
Switch device Monitor to "Tape" position
Start recording
Switch between L and R channels and read the meter "T.H.Dist." scale (same scale/meter for both L and R)
Use the label to switch between 400 and 1000 Hz as desired
Write down results

S/N ratio

Function dial to "Noise-A (-40db)" position
Switch device Monitor to "Tape" position
Start recording
Read the L & R meter on "dB" scale and deduct 40 from the readout
If "Meter Range" switch is at -20dB/0.1% position, deduct another 20
Turn on noise reduction and read again
Write down results

Frequency response

Switch to "Scope" mode
Switch device Monitor to "Tape" position
Select "FR Pink" on the right hand side (similar conditions to normal listening)
Start recording
Select "FR White" for standard specification measurement and set to -20dB
For precise results switch to "FR Sweep"
Take measurements for 0dB and -20dB levels, pin results for each level
Take screenshot and/or record results for +-3db range (Columns R and S)

For recording results with convenience, consider downloading this free spreadsheet template.