Kenwood KA-6004

 Exceptinal Stability of Amplification achieved Constant Current Driving System

The KA-6004 achieves an over-all high level of reliability in every performance phase. If only the strictest requirements are met by each component, then they are included in the full assembly potential of this outstandingly unique amplifier. For example, the pre-amplifier uses a new type of can seal (metal cased) transistor which is capable of off-setting usual characteristic deterioration in S/N ratio resulting from humidity and temperature wear. Low noise PNP transistors have been attached to the top of the equalizer circuit. Also, super-high nichrome evaporated metal film resistors have been used in the feedback circuit in the equalizer stage. Each error thus occurs only within ±1%. These same resistors are also only equipped in all other significant circuits to vastly improve S/N and block S/N age deterioration.

 Linear Frequency Power Output Kept 40 W in 20 Hz to 20 kHz

Kenwood has been improved in output indication. In the conventional way, output was indicated in just one point of 1 kHz. However, in Kenwood's latest way of improving over-all quality guaranteed output is indicated in the entire range of audio frequency of 20 Hz to 20 kHz, i.e. the output is indicated in "minimum point", but not in "maximum point".

The maximum output is a performance figure that implies the dynamic range of the power amplifier, therefore, only the output of 1 kHz will imply the imperfect performance of the amplifier because the output of any amplifier is usually best near 1 kHz. However, as described in the preceding, KA-6004 has the circuits to allow the simultaneous indication of entire performance. With an all stages direct-coupled circuit provided, the output linearity in low pass will be shown by power output data

 Higher Reliability Achieved by Strictly Selected Components

The pre-amplifier employs a new type of can seal transistors that are capable of precluding the characteristic changes, i.e. the characteristic deterioration of S/N caused by humidity and temperature. At the top of equalizer circuit, low noise type PNP transistors are equipped.  The feedback circuit in the equalizer stage employs super-high precision nichrome evaporated metal film resistors, each error within ±1%. The nichrome evaporated metal film resistors are equipped in all other important circuits to prominently improve S/N and preclude age deterioration of S/N.

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Pure-complementary Circuit + Constant Current Driving

The KA-6004 employs Kenwood's exclusive Constant Current Driving system in the pure-complementary and direct coupling driver stage. The highest stability in the amplification is now obtainable. By minimizing crossover distortion and by improving phase characteristics, the KA-6004 guarantees superb performance quality from ultra low range to far above the limit of audio frequency. It also prevents performance from deterioration caused by the deviation in power voltage. Kenwood has overcome the last problem-instability-remaining in direct coupling amplification. The refined reproduction is fully enjoyable.

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Protection Circuit

All stages direct-coupled circuit in KA-6004 includes constant current driver circuit capable of amplifying from DC. The driving way will amplify faithfully the superlow pass, i.e. plus  minus several Hz of the frequency picked up by cartridge on bowed record plate and wow-fluttered turntable, thus the faithful amplification will permit unnecessary critical load on speaker. In addition, if direct current input should be applied, burning of voice coil may by caused.  To prevent the preceding troubles in KA-6004, a protecting circuit is employed to cut superlow pass of 10 Hz or less in order to protect speaker against overload.

 Exceptional Dynamic Range

The equalizing stage of preamplifier has been entirely redesigned to obtain exceptionally wide dynamic range. The KA-6004 assures 420 mV p-p maximum input level (at 1 kHz). Any fortissimo peak can faithfully reproduced without saturation. Further, thanks to the minimized RIAA deviation of within ±0,2 dB, playback with real high fidelity is guaranteed.

Attenuator Type Tone Control

Attenuator is employed in tone control, +10 dB to -10 dB is covered by 2 dB controlled. Left and right characteristics are correctly coincided, so that no unbalance will be caused in tone control.

In conventional volume type, frquency characteristic is not perfectly flat even at zero degree, but is waved. In KA-6004, with tone control positioned at "Off", tone control circuit is neglected, so that frequency characteristic is kept correct.

Noise Filter

Low cut filter has two turnover points, i.e. 40 Hz and 80 Hz controlled, and sharp attenuation characteristic of 12 dB/oct. The filter will also protect speaker, with protection circuit associated, againt large signal inputted in low pass.

High cut filter has a higher turnover point, i.e. 7 kHz which will reduce noise only without damaging desired tone, and an easy attenuation characteristic of 6 dB/oct.

Input Selector

The KA-6004 is versatile for input program sources. It features input jacks for 2 pairs of phono, 2 pairs of Aux, tuner and microphone.  A program source on operation is shown by luminous indicator on the front panel.

Two Systems of Tape Monitor

Two systems of tape monitor circuits, i.e. A and B are provided to allow simultaneous activation of two decks.  Mutual dubbing is easily allowed by switching only.

Microphone Input

Mic input terminals are equipped on front paanel, so that right-side two systems of microphones will allow so easier operation. Since selector positions are independent, the input may be used sufficientlyfor microphone amplifier.

Push Button Type Speaker Selector

Two pair of speaker terminals, i.e. A and B may be changed by push-button correctly locked. With A and B pushed at the same time, simultaneous activation is allowed.

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One Touch Type Speaker Terminals

Speaker terminals are of one touch connection type which allow easy and correct coupling, so that the system will eliminate any trouble on speaker connection.

Loudness Control

On a level of -30 dB, low pass is 100 Hz with +8db and high pass in 10 kHz with +3 dB, both provided higher than the conventional, so that the control will supplement low and high pitched tones.

Specifications

Continuous Power Output: 

Both channel driven: 

40/40 watts  into 8 Ω at any frequency from 20 - 20,000 Hz

43/43 watts into 8 Ω at 1,000 Hz

57/57 watts into 4 Ω at 1,000 Hz

Each channel driven:

55/55 watts into 8 Ω at 1,000 Hz

70/70 watts into 4 Ω at 1,000 Hz

Dynamic Power Output (IHF): 

130 watts per channel into 8 Ω at 1,000 Hz

220 watts per channel into 4 Ω at 1,000 Hz

Total Harmonic Distortion: 

less than 0,5% at rated output from 20 - 20,000 Hz;

less than 0,05% at -3 dB rated output

Intermodulation Distortion (60 Hz; 7,000 Hz; 4:1): 

less than 0.3% at rated output;

less than 0,05% at -3 dB rated output

Power Bandwidth (IHF):  10 Hz to 50,000 Hz

Input Sensitivity/Impedance (for rated output, at 1,000 Hz):

Phono 1:  2,5 mV/50 kΩ

Phono 2:  2,5 mV/ 50 kΩ

Tuner:  200 mV/ 100 kΩ

Aux 1, 2:  200 mV/ 100 kΩ

Tape Play A & B:  200 mV/ 100 kΩ

Mic: 3 mV/50 k Ω

Main Amp. Input:  1 V/ 50 kΩ

Recording Output (below rated input):

Tape Rec A & B:  200 mV

DIN connector:  40 mV

Signal-to-Noise Ratio (below rated output): 

Phono 1 & 2:  68 dB

Mic: 70 dB

Tuner:  75 dB

Aux 1 & 2:  75 dB

Tape Play A & B:  75 dB

Noise at Minimum Volume Control:  0,3 mV at 8 Ω, 0,000012 milli watts

Damping Factor:  32 at 8 Ω load; 64 at 16 Ω load

Speaker Impedance:  accepts  4  to 16 Ω

Bass Control:  ±10 dB at 100 Hz (with 2 dB step switch)

Treble Control:  ±10 dB at 10,000 Hz (with 2 dB step switch)

Low Filter:  40 Hz and 80 Hz cut off, 12 dB per octave

High Filter:  7,000 Hz cut off, 6 dB  per octave

Loudness Control (-30 dB):  +8 dB at 100 Hz; +3 dB at 10,000 Hz

Switches:

Speaker :  A, B (ON-OFF at push switch)

Selector :  Aux1, Aux 2, Tuner, phono 1, Phono 2, Mic

Mode :  left, Right, Stereo, REV, Mix

Tape Monitor :  Dubbing, (A→B), A Play, Source< B Play, Dubbing (B→A)

Others :  Low & High Filter, Loudness, Muting, Power

AC Outlets:  1 switched & 3 unswitched

Power Requirement:  110 - 120 V/220 - 240 V AC, 50/60 Hz

Power Consumption:  235 watts at full power; 15 watts at no signal

Dimensions (W x H x D):  435 x 153 x 300 mm (17-1/8 x 6-1/32 x 11-13/16 inch)

Weight:  11,5 kg (25,4 lbs)