Distortion Null, VCA Gain Adjust | Solid State Logic 82S6XL010D

XLogic Multichannel Compressor Owner’s Manual

Distortion Null

Equipment Required:	Calibrated audio oscillator, audio distortion analyser and oscilloscope
Test Signal:	1kHz sinewave at +24dBu
Input and Output:	Oscillator to the Input of the channel being tested, Output to the distortion
	analyser. Use the oscilloscope to monitor the measured signal.
Adjustment:	1. Connect the +ve input of the analyser to the test point as shown below and
	connect the –ve input of the analyser to a 0VA test point. Note that the circuitry
	at this point is balanced and so there are two measurements and two adjustments
	per channel. Adjust for minimum THD (< 0.007%).
	Input	Measure	Adjust
	Left (+ve)	TP31	VR24
	Left (–ve)	TP32	VR23
	Right (+ve)	TP29	VR22
	Right (–ve)	TP30	VR21
	Centre (+ve)	TP27	VR20
	Centre (–ve)	TP28	VR19
	LFE (+ve)	TP21	VR14
	LFE (–ve)	TP22	VR13
	Left Sur (+ve)	TP23	VR16
	Left Surr (–ve)	TP24	VR15
	Right Surr (+ve)	TP25	VR18
	Right Surr (–ve)	TP26	VR17

2.Finally, re-connect the analyser to each output in turn and adjust the +ve distortion null to see if any reduction in THD can be achieved.

Equipment Required:		Calibrated audio oscillator, audio level meter, oscilloscope and a (digital) DC
		voltmeter
Test Signal:		1kHz sinewave at +20dBu
Input and Output:		Oscillator to the Input of the channel being tested, Output to the level meter. Use
		the oscilloscope to monitor the measured signal.
Unit Setup:	1.	Switch the Master Fader IN.
	2.	Using the DVM, measure TP5 on the upper card (629607) and adjust the front
		panel Master Fader for –2.00V ±1mV (which equates to 40dB attenuation).
Adjustment:	1.	Connect the audio level meter to each output in turn. Measure each channel,
		adjusting the appropriate preset for –20dBu ±0.1dB (which equates to 40dB of
		attenuation).

Page 12