Solid State Logic X-Logic Series owner manual Dynamics Adjustments, Distortion, D-4

X-Rack Owner’s Manual

D.3.5 Measurement Conditions

Signal applied to Input, output measured at Output. All pots anti-clockwise and switches ‘out’ except for Dynamics ‘in’.

THD + N (+10dBu applied) < 0.01% at 1kHz

Signal at +20dBu applied to Input, Compressor Threshold set at –20, Compressor Ratio adjusted to give +4dBu at Output. RMS sensing mode selected.

THD + N	< 0.3% at 1kHz
(Fast Attack Mode) †	< 0.05% at 10kHz
THD + N	< 0.03% at 1kHz
(Slow Attack Mode)	< 0.05% at 10kHz

† LF distortion is consistent with attack and release time constants.

Output Headroom	> +26dBu at onset of clipping
Frequency Response	±0.2dB from 20Hz to 20kHz
–3dB at 130kHz
Noise	< –88dBu

D.4 Calibration Information

The X-Rack Dynamics module is factory calibrated and should only need calibration if a potentiometer or other component has been replaced or if it is suspected that there is a problem with calibration.

In each of the following instructions it is assumed that the lid has been removed and that power has been applied. It is also assumed that unless otherwise specified, all switches are released and all front panel potentiometers are at unity or minimum position as appropriate. The required accuracy for each adjustment will be specified along with the target value. All level and distortion measurements should be made with audio-band 20Hz to 20kHz filters unless otherwise specified.

All presets are accessible from the top of the unit.

Note. The unit should be allowed to warm up with power applied for at least 15 minutes prior to any adjustments being made.

D.4.1 Dynamics Adjustments

If the dynamics circuitry requires adjustment the following procedure should be followed in the order shown. All presets are on the 629618 card.

Equipment Required:		Calibrated audio oscillator, audio distortion analyser, audio level meter,
		oscilloscope and a (digital) DC volt meter.
Test Signal:		1kHz sine wave unless specified otherwise, level as specified.
Input and Output:		Oscillator to Input A (or B), Output to either the distortion analyser or the
		level meter, as specified below. Use the oscilloscope to monitor the
		measured signal.
Unit Setup:		Switch the dynamics IN and the EQ and Filter sections OUT, set all of the
		dynamics controls anti-clockwise and release all switches.
D.4.2 Distortion
Adjustment:	1.	Connect the distortion analyser to the Output and set the oscillator level
		for +20dBu.
	2.	Adjust VR12 for minimum distortion (< 0.02%).

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