DIATONE DA-U750

Commentary

The OCL system directly connected to the front stage realizes high power.
As for the temperature drift of the DC voltage at the output terminal, a new amplifier circuit is adopted which shows extremely small drift over a wide temperature range, and high performance is achieved by using parts with large current capacity.

An ultra-low noise transistor developed by Diatone low-concentration diffusion technology is used for the first stage differential amplification.
Compared with conventional low-noise transistors, the 1/f noise is reduced by approximately 2 dB and the dynamic range is also improved.

The power stage and driver stage use a pair transistor with uniform bare characteristics to reduce distortion in open loop.
This reduces distortion at low output and contributes to the expansion of the dynamic range.

In order to shield it from high heat and magnetism generated by the power block, it is clearly separated, pre-block is placed on the front part and it is also shielded.
As a result, the temperature can be kept 10 ℃ lower than that of the power block under normal operating conditions, and the stability of the transistor with high temperature dependence and the reliability of each component are improved.
The power section and pre-section are connected under both blocks, so it is designed to be less susceptible to aging.

Equipped with a presence control that can amplify the mid-range in 1 dB steps.
The center frequency can be switched between 800 Hz and 2000 Hz.

The tone control circuit has a circuit configuration in which the time constant circuit is disconnected at the flat position to obtain a flat frequency characteristic.

Both the tone control amplifier and the presence control independently employ highly stable amplifiers with a wide linear operating range of transistors.

A 22-contact attenuator is used. Both attenuation deviation and gang error are within 1 dB of attenuation up to 28 dB and within 1.5 dB of attenuation 30 dB or higher.

Power ratio 2.8.

Model Rating

Type	Pre-main amplifier
Power Amplifier Unit
Output (both channel operation)	20 Hz to 20 kHz : 85W + 85W (4 Ω) 60W + 60W (8 Ω) 1kHz: 90W + 90W (4 Ω) 65W + 65W (8 Ω)
Harmonic distortion factor	0.1% (Rated) 0.05% (at 1W)
Cross modulation distortion factor	0.05% (at 1W)
Power bandwidth	10 Hz to 30 kHz
Damping factor	80 (8 Ω)
Residual noise	0.4mV
Input Sensitivity / Impedance	1V/60k Ω
Preamplifier Section
Input Sensitivity / Impedance	Phono1: 2.5mV/50k Ω Phono2: 2.5mV/30, 50, 75k Ω High Level Input: 150mV/50k Ω
Output Level / Impedance	Pre Out: 1V/1k Ω Rec1, 2 : 150mV/1k Ω
Harmonic distortion factor	0.05%
Frequency characteristic	Phono(RIAA STD): 20 Hz to 20 kHz ± 0.3 dB High Level Input: 20 Hz ~ 20 kHz + 0 -0.5 dB
Presence control	± 3 db (800, 2 khz)
Tone control	Bass : ± 10 dB (100, 50 Hz) (Turnover 500, 250 Hz) Treble : ± 10 dB (10, 20 kHz) (Turnover 2.5, 5 kHz)
Filter	Low : 15, 40 Hz (12dB/oct.) High : 9, 15 kHz (12dB/oct.)
Phono allowed input	300 mv (1 khz 0.1% Distortion)
Input reduced noise	Phono:-120dB(V) High Level Input:-100dB(V)
<General>
Pwer	AC100V 50Hz/60Hz
Power consumption	130W
External dimensions	Width 425x Height 148x Depth 387 mm
Weight	17kg