Yamaha ca 1000

Page 2

CIR CU IT DESCRIPTIONS

SRPP ISHUNT-REGULATED PUSH-PULL) CIR-
CUIT
Features: Thanks to efficient use of power this
circuit features a large dynamic range.
Superior frequency response, lower noise
and distortion ratio in following stages
due to higher output impedance.
The SRPP circuit provided the above features to
pre-amps during the tube era. It is composed of DC
elements in series, but if we look at it as an AC
circuit from the load side, the top and bottom
elements appear to be AC, connected in parallel, so
that the input impedance is high and output
impedance low.

gather data on the best characteristics for tube and
transistor systems. yet this unit uses a combination
of two selected FETs in the SRPP circuit for out-
standing performance characteristics.

2. iSPEClAL YAMAHA TONE CONTROL SYSTEM
This circuit is composed of a CR damping circuit,
used generally in audio equipment, of the negative
feed back type.

ei

evo- we

02 When (+I input is fed to OI,
reverse phase voltage occurs
at RS.

VB RS

0| the "ei" input, causes 02 to

Voltage, opposite in phase to

IN
operate in a push-pull modes

RA RL Output is available from

0-..-
+3

iNO-Akg Ql
so 0:
Fig.2

02

E .
C Fig. 1 terminal RL.

In this circuit 02 serves as load resistance for 01 by
using the gain from the FET's high output impedance.
Furthermore, it is designed for a high RL factor.
This is to handle the high gain with less distortion.
In addition to a low distortion ratio, high S/N ratio,
large input capacity and precise R IAA dnaracteristics,
the CA<1000 equalizer amp is not influenced by
broadcast signals even in high field strength areas,
and will accept various types of cartridges.

These features are all assured by the primary
FET stage. Because these elements provides charac-

teristics close to those assured by squared factors,
that random harmonic distortion is reduced and
noise characteristics, especially pulse noise is ex-
tremely low. Noise factor in the transistor-
collector current is minimal (near IOpA), so that
ideally the equalizer amp primary stage current
should be near this figure, except that this would
make it difficult to provide sufficient input power.
Drain current does not affect this figure, either,
so it can be decreased by the supply of more
current.

The CA-IOOO is designed for IrnA drain current, so
that primary amp stage input is dozens of times
greater than the transistors IQuA.

These excellent FETs were not used in high-fidelity
amplifiers until now because of their smaller gain
per unit, and because the IDSS (gate shutoff current)
scatter was too large. It has also been difficult to

When the treble from the circuit shown in the
figure is boosted, the paralleicoupled impedance
in the first stage 01 emitter rises in range and is
reduced in amount. In other words, the N F decreases,
boosting the treble tones. On the other hand, to
cut the treble a special treble damping effect is
produced by lowering the impedance of the contact
point between the R1 (connected to the last stage
collector) and the output terminal. Bass tone
control is carried out in the same way.
Because the CA.1000 is the same as the first-quality
three-stage direct-coupled equalizer amplifiers
used in the most expensive audio equipment, the
S/N ratio is superb and distortion is almost un
measurably low. In addition, when the tone controls
are set for flat response, gain at 25dB is SOdE
negative feedback for outstanding stability.

3. CONTINUOUS LOUDNESS CIRCUIT

The continuous loudness circuit used in the CA-IOOO
corrects the weak point found in conventional
loudness controls; its effect is graduated according
to the volume control setting for ideal loudness
characteristics at any volume level.

A conventional loudness circuit, as shown in the
figure, is a time constant circuit connected to the
middle volume tap. Its characteristics are changed
according to the volume control setting as shown in
Fig. 3, but it is impossible to adjust it to match
speaker performance or room acoustics. The con-
tinuous loudness circuit in the CAeIOOO, however.
is a circuit connected behind the volume circuit
(actually, behind the tone control circuit). This
solves the above problem, allowing the listener to
use the circuit to achieve ideal listening character-
istics. (Fig. 4)