McIntosh C500C Owner's Manual download pdf (Page 34)

Figure 98

balance and freedom from control noise.

The Volume Control

on the Front Panel of

the C500 is actually a

special digital optical

encoder. As the Volume

Control is rotated, a

beam of Infra Red Light

is picked up by two in-

ternal sensors as a series

of digital pulses. Refer

to figure 97. The number of and time between

pulses are counted by a Microprocessor which

in turn controls the McIntosh designed Preci-

sion Electronic Attenuator that provides 213

steps in 0.5dB increments and maintains the

channel balance to within + 0.1dB.

With most Preamplifiers the Volume Con-

trol is placed ahead of the Amplifying Cir-

cuitry, refer to figure 98 on the next page, ex-

ample No.1. This design provides a great dy-

namic range and freedom from input overload,

but the background noise level is higher espe-

cially at lower settings of the volume control.

In example No. 2, by placing the Volume Con-

trol after the Amplifying Circuitry there is a

reduction in dynamic range and input overload

of the Preamplifier, but has the benefit of

lower background noise levels. The only cor-

rect way to design a high performance Pream-

plifier is with two volume controls, refer to

example No.3. This provides the benefits of

wide dynamic range, freedom from Input over-

load and a background noise level that actu-

ally goes down as the volume control setting is

reduced. The actual improvements in

this McIntosh design achieve a noise

floor of 118 dB, refer to figure 99.

The special controlling circuitry for

this dual volume control design is

known as the McIntosh “Dynamic

Control Multiplexer”.

Fully Balanced Circuitry

To compliment the level of perfor-

mance achieved in one of McIntosh’s

famous Power Amplifiers with Quad

Balanced Circuitry, the C500 Pream-

plifier also utilizes fully balanced cir-

cuitry. This design topology allows for the virtual cancela-

tion of all forms of distortion, both audible and measurable,

along with extremely low background noise levels.

In the typical Preamplifier, one set of circuits have to

amplify the positive and negative going parts of the audio

sound wave form. In the C500, the implementation of fully

balanced circuitry has the positive going audio sound waves

amplified by one set of circuits. In a similar manner the

negative going audio sound waves are amplified by another

set of circuits. Refer to figure 100. Audio signals connected

Figure 97

Sensors

Optical Disc

Infrared LED

Figure 99

Signal to Noise vs. Volume Level of the

C500 Preamplifier versus High Performance

Mechanical and Electronic Volume Controls

-95

-100

-105

-110

- 115

-120

-95 -85 -75 -65 -55 -45 -35 -25 -15 -5 5 15

Volume Level (dB)

Signal to Noise (dB)

Mechanical

Electronic

C500

1 2 ... 29 30 31 32 33 34 35 36 37 38 39 40

Comments to this Manuals

No comments

McIntosh C500C Owner's Manual Page 34

Comments to this Manuals

Related products and manuals for Audio amplifiers McIntosh C500C