Madrigal Imaging N38 manual Main Front Power Amplifier

Surround sound processors should not be in a tape loop

Surround sound processors and the Nº38

Wiring Diagram with a Surround Sound Processor

The last remaining alternative would seem to be to insert the decoder “within” a preamplifier by hooking it up in a tape loop. Unfortunately, this set-up returns the Left and Right outputs of the decoder to the preamplifier, where they can be inappropriately changed without changing the Center and Surround outputs. It is therefore inappropriate to place surround sound decoders in a tape loop.

It would seem that there is no way to properly integrate a surround sound processor with a preamplifier for a high quality, dual-purpose system.

The Nº38 solves this dilemma by virtue of a specially designed surround sound processor interface. When you select the “ssp” alias for a particular input on the Nº38, the output level and balance controls are defeated and the preamplifier operates in unity gain mode, passing through whatever signal enters that input without changing its volume in any way. In fact, the display indicates that a line-level signal is being “passed through” unchanged by showing “LINE” in the display.

Thanks to this design innovation, it is possible for the first time to correctly integrate a surround sound processor with a preamplifier, sending the processor’s Left and Right outputs through the Nº38 (and on to the power amplifier for the main front speakers). Since the output level of these channels cannot be changed by the Nº38 while in “ssp” mode, the preamplifier cannot corrupt the careful calibration of the processor’s output levels. And since the video sources are fed directly to the processor’s audio input(s) at a line level, input calibration cannot be disturbed by the preamplifier.

video 1			video 2				video 3	video 4	LS		LS
									RS
										Surround Power Amplifier	RS
			Surround Sound Processor						Ctr		Ctr
						LF	RF		Sub	Center/Sub Power Amplifier	Sub
display									RF		RF
intensity							inverted
						mode	polarity			Main (Front) Power Amplifier
								PREAMPLIFIER	LF		LF
	monitor		record select			balance		Nº 38
mon	1	2	3	4	5	6	mute	standb
o								y
									Listening Room

Note: the Nº38 will not allow an input with an “ssp” alias to be selected during initialization, since allowing a line level signal to pass through unattenuated at start-up presents a potential hazard to your loudspeakers.

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