Audio Database

The pictorial image of Integra P-306

ONKYO Integra P-306
100,000yen(around the 1979 time)

The stereo preamplifier which adopted W and a super servo scheme.

W super servo scheme is a scheme which cancels in equivalent the unnecessary component which suppresses the cross modulation by unnecessary super-low-pass one, and originates in the impedance between groundings.
By using of an attached super servo code, the + side input terminal of output amplifier detects and oppresses a harmful super-low-pass component,Moreover, the servo amplifier by the side of - is canceling the harmful component generated by a part for a resisted part of the connecting cord with a main amplifier itself, or an inductance, contact resistance, etc., and has prevented the interference and separation failure between channels.

In order to employ the property of a super servo efficiently, man-month type to MC type has adopted the equalizer amplifier of the one stage scheme corresponding to all the cartridges by the gain up of equalizer amplifier, without the amplifier for MC also using a step-up transformer.
In the first rank differential-amplifier part, the heat joint treatment of two super-low-noise high Gm FET is carried out in an aluminum case, and visitor thermal noise is also suppressed with the thermal balance modification.
Moreover, the improvement in S/N is aimed at by making the Para interconnection of the differential part and lowering an impedance. In order that this differential amplifier may stop a mirror feedback capacity, it was made the cascode interconnection and has acquired the larger frequency characteristic.
Moreover, big nakedness gain was secured by the 2nd step differential amplifier and the differential amplifier with the 3rd step current mirror, and the stability and low distortion which were excellent in high gain amplifier using the partial feedback by pole setups are realized.
Furthermore, the final stage is transmitting the signal to the following stage amplifier by the low distortion by the Class-A push pull that there is no unreasonableness also in the heavy load of a high region.

The direct tone scheme is adopted as a tone control.
It consists of only passive elements, and since it is a peculiar circuit system with which a harmful capacitor does not enter in a signal passage path, a sound field correction can be performed, without carrying out a tone-quality failure.

Since the super servo scheme was adopted as output amplifier, an output capacitor did not need to be put in, and since a low-pass time constant is determined only in a servo circuitry, it has canceled the shortage of low-pass at the time of a low-impedance load intensity.

It has linked each circuitry block directly with the bus (bus-bar) line made from a copper plate, and has prevented low-impedance-izing of a feed line, and the cross interferencee of each inter-block while NF type constant-voltage stable circuitry which achieved the right-and-left independency is used for a power-source part.

Non-magnetic material, such as copper, aluminum, and a brass, is used for shielding material or each fraction.
Thereby, the magnetic flux generated from a circuitry generated the high order higher harmonic (3rd higher harmonic mainly harmful in Hearing impression) with the nonlinearity of the magnetic path, and has prevented having an ill effect on a tone quality.

Since all cartridges are suited, the cartridge selector is carried.

The influence on the tone quality by a placement of each part, leading about of a line, etc. is considered, and the placement analysis is conducted later on in the order of a signal system.
For example, in order to input a signal into a predetermined circuitry by a short-haul as much as possible, the direct change by a remote-control switchpoint was adopted, and the failure of the crosstalk by leading about of a signal line or a high region property is prevented.

The study and testing which were put into practice among all the circuit component part were added, and the part which has a margin in all, such as not only a property but an endurance, a feeling of a using, etc., is adopted.
For example, the input pin jack treating a weak electric current gives a pure gold thickness plating, and consideration is carried out so that the influence of contact resistance may not appear in a tone quality.


Rating of a mode
Form W and a super servo scheme stereo preamplifier
Input sensitivity/impedance Phono MC: 130 microvolt/100ohm, 330ohm
Phono High Gain MC: 2.5mV/100 ohm
Phono man month: 2.5mV / 47kohm, 100kohm
Tuner, AUX, Tape Play:150mV /, 47kohm
An Output voltage/impedance Tape Rec: 150mV / 2.2kohm
Output: 1.5V, a maximum of 20V/220ohm
Phono maximum permissible input (THD 0.05%)
MC: 17mV(1kHz)
man month, High MC : 300mV(1kHz)
THD (THD, 20Hz - 20kHz)
Volume-3dB, Output 3V
MC: 0.01% or less
man month: 0.003% or less
Tuner, AUX, Tape: 0.003% or less
Cross modulation distortion (SMPTE 70Hz:7kHz=4:1) 0.003% or less (at the time of an Output power)
SN ratio (IHF-A network input shunt) MC:69dB
Tuner, AUX, Tape: 100dB
Tone control (Volume-20dB) Bass: 70Hz, ±8dB
Treble: 20kHz, ±8dB
Filter property High Cut: 7kHz, 6dB / oct
Subsonic Cut: 15Hz/20 Hz, 6dB / oct
Muting -20dB
Transient killer operating time Power on:7sec
Power off:100msec
The semiconductor used Transistor: 47 pieces
FET: Six pieces
IC: Four pieces
Diode: 37 pieces
Power source AC100V, 50Hz/60Hz
AC outlet A total of a maximum of 1000W
Power-switch interlock: Two lines
Power-switch un-interlocking.: One line
Power consumption 20W (Electrical Appliance and Material Control Law)
The maximum Dimensions Width 450x height 99x depth of 407mm
Weight 7kg