Yamaha P-2200, P-2200/2201, P-2201 most difficult loads, even in the "mono" mode.

Intermodulation Distortion, or I.M. is characterized

by the appearance in the output waveform of fre-

quencies that are equal to sums and differences of

integral multiples of two or more of the frequencies

present in the input signal. The difference between inter-

modulation distortion and harmonic distortion is that

two or more different frequencies must be present to

produce intermodulation distortion (only one frequency

is needed for harmonic distortion to appear), and that

intermodulation distortion products may not be

harmonically related to the original frequencies. Like its

harmonic distortion figure, the intermodulation dis-

tortion in the P-2200 is low enough to be virtually

inaudible even in the most critical situations.

Dynamic Frequency Response Shift is related to both

harmonic and intermodulation distortion. When high-level

low and high frequency signals are present in the same

waveform,

the

high

frequency

signals

"ride"

top

the

low frequency waveforms (see Figure 65, Page SEVEN 1).

amplifier

headroom

inadequate,

the

low frequencies

may

"push"

the

high

frequencies above the

output

limits

of the amplifier, clipping them off the waveform (Figure

65C). The low frequencies may remain unaltered, but the

high frequencies are severely reduced. At the same time,

harmonics of the high frequencies are produced which

add to the super high frequency content of the signal.

Thus, along with the distortion created by the clipping,

the frequency response of the original signal is drastically

altered. This type of distortion can be reduced by in-

creasing system headroom (using a more powerful

amplifier like the P-2200), and by biamplifying the

system as discussed on Page SEVEN 1.

The extremely low distortion figures of the P-2200

indicate its overall quality and mean that its sound will

be precise and natural.

FREQUENCY RESPONSE (Refer to Figures 5 & 16)

The frequency response of the P-2200 describes the

variation in its output signal level with frequency when

the

input

signal

held constant. The extremely

flat

frequency response curve of the P-2200 is an indication

of its overall quality and its ability to respond to upper

and lower harmonics of signals all the way to the

extremes of the audio spectrum.

Because extreme stability is necessary for some types

of commercial sound applications, notably 70-volt lines

(see Page SEVEN 11), some manufacturers restrict fre-

quency response or allow relatively high distortion in

return for increased amplifier stability. The P-2200, on

the other hand, has excellent frequency response and

ultra-low distortion, yet is inherently stable under the

most difficult loads, even in the "mono" mode.

The frequency response of the P-2200 has been

intentionally limited, however, at very low frequencies

(sub-audio). Because of this, severe low frequency

transients, or DC offset, appearing at the input to the

P-2200 are unlikely to damage a speaker load. Other

amplifiers which are DC coupled throughout may have a

"flatter"

sub-audio frequency

response,

but

this

makes

them capable of amplifying dangerous DC input voltage

or sub-audio transients and delivering them (at high

power) to a speaker.

OFFSET VOLTAGE

This specification indicates the amount of DC voltage

naturally present at the output of the amplifier. A high

DC voltage could damage the loudspeaker load; the

±10mV (10 one-thousandths of a volt) level from the

P-2200 is insignificant.

UNIT STEP FUNCTION RESPONSE (Refer to Figure 27)

A unit step function is like the leading edge of a

square wave; it goes up, but never comes down. The

response to this input indicates the output of the P-2200

for a DC input signal which might come from a faulty

direct coupled preamplifier or mixer. Note that the

P-2200 will not reproduce a DC voltage fed to its input,

thus adding an extra measure of loudspeaker protection.

POWER BANDWIDTH (Refer to Figures 3 & 14)

The power bandwidth of the P-2200 is a measure of

its ability to produce high power output over a wide

frequency range. The limits of the power bandwidth are

those points where the P-2200 can only produce 1/2 the

power that it can produce at 1000Hz. While the

frequency response is measured at relatively low power

output (1 watt), the power bandwidth is measured at the

P-2200's full power output (before clipping). The power

bandwidth

the

P-2200

quite

flat

and extends

200kHz, well beyond the limits of the audio spectrum.

The wide power bandwidth of the P-2200 means that

it can reproduce high level upper harmonics of a signal

as easily as it can reproduce mid-range fundamentals. It

means

that

you

get

full

power performance

from

the

P-2200 over the entire audio frequency spectrum. This is

especially important when the amplifier is called upon

to reproduce musical material with high energy over a

wide frequency range, such as rock and roll.

PHASE RESPONSE (Refer to Figure

)

The phase response of the P-2200 is a measure of the

amount of time delay it adds to different frequencies.

An amplifier with perfect phase response would introduce

equal time delay at all frequencies reproduced. The

P-2200's worst case phase shift of -10 degrees at 20kHz

corresponds to a 1.4 microsecond (1.4 millionths of a

second) delay period which is insignificant in even the

most critical audio applications.

Fig. 29 - Waveform of Amplifier with Poor Phase Response.

An amplifier with poor phase response would change

the shape of a waveform that was made up of a funda-

mental frequency and several harmonics by delaying

each harmonic differently. The effect might be similar

to that shown in Figure 29.

CHANNEL SEPARATION (Refer to Figure 10)

This specification indicates the output from one

channel when a signal is fed to the other channel. The

P-2200's channel separation is very good, which means

that

even

critical

stereo programs

will

be unaffected by

crosstalk between channels.