Tascam 34B ready for speed measurement. Test tape loaded and frequency counter connected.

(I always start the checks with speed measurements, as it can affect the other measurements if the recorder runs at the wrong speed). A test tape and frequency counter is needed.
A multi channel recorder has a circuit board for each channel. After removing the bottom cover, one has access to the boards
for adjustments.
 

VU meters showing 0dB when running the calibration tape.

Above is the recorder running the "output level calibration". 1000Hz at 250nWb/m.
I adjust the output level to be -10dBV (0,315V) on each channel. Next, I adjust the VU meters so that they show
0dB. Test tape and multimeter (or oscilloscope) is needed.
A 50 kiloOhm resistor is also needed at the output, as specifications say that output level should be 0,315V across a 50 k load...

Signal generator and oscilloscope connected for input level measurements.

For input measurements, no test tape is needed. The first part is an electrical measurement where a 1000Hz tone at 0,315 V is fed into the input connectors, and VU meters are adjusted to show 0dB.
The output level is also adjusted for 0,315V.
These adjustments only have to do with the amplifiers in the recorder. No tape is needed!

The final part is to tune the recorder for the recording tape you will use.
The adjustment is made by applying 0,315V to the input and adjusting a recording amplifier so that the recording will be
"0dB" when you play the tape.
There is also something called "bias" that must be tuned for the tape you are going to use.
I may write more about that later if anyone is interested...
 
 

OTARI 5050

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