7

Board Test Equipment and Test Procedure

for Intersil HCA600ACREF Amplifier

Equipment required for evaluation of the Intersil

HCA600ACREF Amplifier is as follows:

1. Few bench supplies can deliver the rated voltage and

current for this amplifier. Furthermore, most linear bench

supplies cannot sink current. If at all possible a 1KVA

transformer (92V-0-92V) and rectifier should be used to

supply main power. See Figure 6. Bench supplies can be

used to provide bias as shown on the next page.

2. Three 12V, 500mA Power Supplies (if transformer with the

required secondary windings is not available).

3. Distortion Analyzer such as the Audio Precision System

One or System Two or equivalent.

4. Load resistors, 8

Ω, 500W and 4Ω, 1000W and a fan.

5. Associated connectors and cables.

6. HCA600ACREF Amplifier Board.

Test Procedure for Evaluation of HCA600ACREF

1. The power supply sequencing is not critical with one

exception. The -12V must be applied at the same time or

before the +12V. If not, the amp may not start.

Frequency sweeps should be limited between 3Hz and 80kHz

at high powers. Amplitude vs. frequency sweeps at full power

will not damage the amplifier. Nevertheless, high frequency

(>10kHz) high power continuous sine wave testing may result in

a thermal shutdown and in extreme cases failure, so this should

be avoided. Music does not contain high frequency high power

signals so this is not a concern in real applications.

WARNING: This amp is DC coupled. Do not apply DC to

the input. In applications, a DC blocking cap is required in

the preamp or between the preamp and the amplifier. For

example, a 2.2

µF film capacitor between the preamp and

the -input will roll the frequency response off at 7Hz (10K

input impedance).

2. THD measurements are not valid if the AP filters are not

used. The AP interprets the carrier of a class D amplifier as

noise. Filters must be used to remove the carrier. Always

make sure that either the 22, 30 or 80kHz filters in the AP

are selected. The 80kHz filter does not attenuate the carrier

completely, and if it is selected an external 80kHz RC filter

should also be used. This filter must use a high quality cap

so that it does not contribute to THD. A 10K metal film

resistor with a 180pF polypropylene cap does the job well.

If the carrier is visible with a scope on the reading output of

the AP, then the AP is including the switching frequency in its

THD+ Noise calculations. The number is not valid.

Selecting the 80kHz filter and using a single pole external

80kHz low pass filter allows the 2nd, 3rd and 4th harmonics

of a 20kHz signal to be observed.

The external RC filter should also be used when measuring

IMD and CCIF.

Schematic Diagram of HCA600ACREF Board Test Setup

CAUTION: Remove all power when inserting or removing the amplifier board. Make sure power supply capacitors are discharged or damage to the

amplifier may result.

12V

+

-

TO AUDIO GENERATOR

TO DISTORTION ANALYZER INPUT

AMPLIFIER LOAD RESISTOR

OUTPUT END OF HCA600ACREF

ANALYZER GND

TO EARTH GND

MAKE SURE SUPPLY

12,000

µF

12,000

µF +

+

IS STABLE WITH

CAPACITORS

F

A

N

A

G

N

D

A

G

N

D

+

I

N

P

U

T

-

I

N

P

U

T

E

N

A

B

L

E

C

L

O

U

T

S

S

F

-

1

2

V

+

1

2

V

P

G

N

D

P

G

N

D

P

G

N

D

+

B

U

S

+

B

U

S

-

B

U

S

-

B

U

S

1

2

V

F

L

T

C

L

O

U

T

12V

+

-

12V

+

-

+

120V

-

+

120V

-

HCA600ACREF