KENWOOD L-01A

Commentary

A pre-main amplifier that eliminates magnetic distortion by making it completely non-magnetic.

The L-01A is entirely made of non-magnetic material in order to suppress magnetic distortion, which has a large effect on audibility.
First of all, the transformer, which is a mass of magnetic material and magnetic flux, is separated from the signal amplification section and housed in a separate case. Also, the construction of the signal amplification section has been completely changed from the conventional one. The sub-panel and part of the panel case are made of new reinforced nylon, the back panel is made of thick phenolic laminate, the left and right side plates are made of aluminum, and the bottom plate is made of wood and non-magnetic materials according to the strength and the purpose of use.
In addition, the heat sink is made of aluminum, the heat pipe and bus-earth are made of copper, and the parts are made of resin condenser, non-grease switch with copper casing, copper styrene condenser, and conductive plastic volume. The entire structure from the casing to the parts is made of non-magnetic material.

It is equipped with a dynamic power supply to realize speaker control in higher dimension.
The L-01A uses a large-capacity transformer for both the left and right channels, far exceeding the conventional scale of 537.6 va. Moreover, by adopting a dynamic power supply in which the power transformer is separated from the signal amplification system, it is possible to increase power without decreasing amplification factor even if the impedance to be connected is changed such as 4 Ω or 8 Ω.
This power linearity makes it possible to bring out the real power even when a speaker with a sharp impedance change is connected.

The power supply unit consists of a separate housing in which only the power transformer is separated from the signal system, and the rectifier circuit is housed in the same housing with the signal system. This system uses AC to increase the current capacity up to the rectifier circuit, and by placing the rectifier circuit near the signal system, the impedance is greatly reduced.
In addition, AC40Vx2 and 3A large-capacity transformers are arranged for the power amplifier for the left and right channels respectively, and AC28Vx2 and 0.5A for the MM equalizer, AC15Vx2 and 0.6A for the MC head amplifier, and large-capacity transformers with dedicated windings for each NF block are used.
In addition, the power supply capacity of the transformer housing including the power transformer for lamp relay and remote is 537.6 va, making up a very strong power supply part for a 100W amplifier.

Equipped with a recout selector, the signal to the Rec out can be freely selected regardless of the input selector.
Also, in the Rec off position, the tape deck connected to the Rec out jack is disconnected and is not affected by the tape deck.

A heat pipe made of 99.96% pure oxygen-free copper with extremely high thermal conductivity is used for heat dissipation. This heat pipe minimizes the loop of electromagnetic waves generated between the final transistors and reduces adverse effects on the signal system.
In addition, by centralizing the high-power section, the heat sink can be placed between the high-power section and the small-signal section, so that the shielding effect is fully exhibited.

The balance jump circuit is adopted from the basic policy that the signal line should not be extended.
When the Balance Jump switch is ON, the signal input from the rear panel passes through the center of the set and is sent to the speaker terminal. This simple circuit configuration reduces the influence from the high power section to the low signal section, and the heat sink blocks the interference to obtain stable performance.

The equalizer amplifier section emphasizes low distortion factor and high SN ratio. The first stage consists of a current mirror load cascode differential amplifier (constant current drive) using a low-noise dual FET, the second stage consists of a constant current load cascode Darlington A-class amplifier, and the last stage consists of a SEPP DC configuration amplifier.
Since the SN ratio of the FET used for the input is hardly affected by the signal source impedance, it exhibits excellent SN ratio even when the MM cartridge is mounted.

The MC head amplifier section has a DC-configuration with an all-stage complimentary service push-pull amplifier circuit using a low-noise transistor at the first stage with a single connection.

The power amplifier section employs a dynamic bias circuit that is completed by TRIO's unique method. Switching and crossover distortion are eliminated from the amplifier by applying a constant bias current to the transistor. It is also a straight DC amplifier that does not have any low-pass capacitors from the tuner or aux jacks to the speaker jacks.
The power amplifier section has a high-gain design. When a record is played back, the circuit is simple with only an equalizer amplifier and a straight DC power amplifier. This increases sound purity.
The voltage amplifier consists of 3-stage differential amplification of first stage cascode-connected FET differentials, the current amplifier consists of inverted 3-stage Darlington, and an EPR (Emitterwith-Polysilicon Barras Resistor) transistor with a wide safe operating range is used in parallel.

Equipped with a subsonic filter.
A non-polar electrolytic capacitor is used for the filter with an emphasis on sound quality, and the cutoff frequency can be switched to two levels.

A newly developed dual resin capacitor with two 63V/18,000 μ F aluminum electrolytic capacitors in a resin case is used for the power amplifier. Low impedance is ensured by the use of low-magnification foil and ultra-high-speed electrolytic solution. In addition, there are three terminals (plus / ground / minus), and the space between terminals is made as small as possible to
As a preamplifier, the power supply circuit of the MC head amplifier section uses a large resin capacitor. Two 25V/2,200 μ F capacitors are used, and two 42V/1,700 μ F capacitors are used for the equalizer.

A non-grease switch is used for the loudness, balance, and recout selector.
The grease and oil used to protect the silver used for ordinary contacts had very poor dielectric properties and adversely affected sound quality. The L-01A uses hard gold plating on the contacts to improve environmental resistance even without grease or oil. In addition, copper is used for the casing to make it non-magnetic.

Oxygen-free copper litz wire is used for wiring to prevent degradation of high-frequency characteristics due to skin effect.

We have adopted a newly developed copper-styrene capacitor that uses copper instead of conventional aluminum foil, and by using copper legs for the lead wires, we have proposed a third harmonic distortion of 20 dB.
The miniature relay also uses gold contacts and twin crossbars to reduce contact resistance.

The volume is a conductive plastic volume that is thick and extremely smooth with a surface smoothness of less than 0.2 μ m, improving the signal-to-noise ratio.

Tantalum film resistors, laminated styrofoam capacitors, polypropylene film capacitors, etc. used in conventional high-speed amplifiers, etc. have been adopted.

Model Rating

Type	Integrated amplifier
<Overall characteristics (Tuner, Tape → SP out (some Phono → SP out)>
Rated Output (Both Channel Operation)	100W + 100W (8 Ω, 20 Hz to 20 kHz) 160W + 160W (4 ω, 1 kHz)
Total harmonic distortion factor (8 Ω)	Phono-SPout: Tuner, Aux, Tape-SPOUT : 0.008% (20 Hz to 20 kHz at rated output) 0.006% (20 Hz to 20 kHz at rated output) 0.003% (1 kHz at rated output) 0.006% (20 Hz to 20 kHz at 1/2 Rated Output)
Frequency characteristic	Straight DC on : DC ~ 400 kHz -3dB Straight DC off : 5Hz/18Hz ~ 400 kHz -3dB
Cross modulation distortion factor	0.003% (60 Hz : 7 kHz = 4 : 1, at rated output, 8 Ω)
Output bandwidth	5 Hz to 100 kHz (IHF, 0.05% distortion rate, 8 Ω)
Damping factor	1000 (8 Ω)
Input Sensitivity / Impedance (Balance off)	Tuner, Aux, Tape play : 200mV/50k Ω Phono MM : 2.5mV/50k Ω Phono MC : 0.1mV/100 Ω
S/N ratio (IHF-A)	Phono MM:90dB Phono MC:72dB Tuner, Aux, Tape play : 110 dB
Subsonic filter	5Hz:6dB/oct 18Hz:6dB/oct
Loudness control (Vol-30dB)	+ 3 db, + 6 db, + 9 db (30Hz/100Hz)
Transient response	Rise time : 0.8 μ s Slew rate : ± 150 V / μ s
Equalizer Section (Phono → Tape rec)
Phono maximum allowable input (1 kHz)	MM : 250 mV (at a distortion rate of 0.01%) MC : 9 mV (at 0.01% distortion rate)
Phono RIAA deviation	20 Hz to 20 kHz ± 0.2 dB
<General>
Output Level / Impedance	Tape rec (PIN) : 150mV/180 Ω
Power outlet	Power switch interlock : 2 systems, 100W Power switch not linked : 1 system, 400W
Pwer	100 VAC, 50Hz/60Hz
Rated power consumption	300W (Electrical Appliance and Material Control Law)
External dimensions	Body : Width 440x Height 156x Depth 452 mm Power Supply : 170 mm W x 156 mm H x 403.5 mm D
Weight	Body : 9.5 kg Power supply : 17.5 kg