Diatone DA-U750 Integrated Amplifier, perfectly working beautiful unit

Special Offer: US$599 including FREE surface shipping to USA, Canada, and major EU countries.

Up for sale is the legendary Diatone DA-U750 integrated amp in an excellent condition. ( fully-overhauled and perfectly working without any issue)

Recently, I have checked, cleaned and fully overhauled this beautiful unit.
The overhauling includes checking all circuit boards, replacing over 80 condensors and other parts, and cleaning all contacts.
The high-performance condensors are used to replace with old condensors.

Its premp quality is legendary and versatile as same as the its bigger brother DA-U850

Also, this DA-U750 use all the same preamp circuitry, power output, and power supply of its bigger brother DA-U850. (¥150,000 around 1975)

The only difference is the power output transistor quantity.

The DA-U750 uses 2 per channel, while the DA-U850 3 per channel. (Two models weigh almost same at 17Kg and 17.5Kg)

The DA-U750 was first introduced to the US market in 1976. (1975 in Japan) This was an expensive top-notch model, retail-priced at JPY98,800 in 1975.

Its suave and world-class performance attracted many admirers at that time.
Especially, its preamp performance would be one of the bests from Japan.
In addition, the versatile functions of the preamp section help users to easily customize the music.

Its circuitry is totally separated between the preamp and power amp sections.
This DA-U750 can be used as a dedicated preamp with high performance and versatility.

The bolts for covers are made of brass (with black coating) (High Quality to the micro details)

A buyer pays only nominal S/H.
The SURFACE shipping to USA costs US$80, while the expedited airfreight to USA costs US$180.


[SPECIFICATION]

Form : Integrated Amplifier

<Power amplifier section>

Output (both ch operation)
20Hz - 20kHz : 85W+85W (4ohms) 60W+60W (8ohms)
1kHz : 90W+90W (4ohms) 65W+65W (8ohms)
THD 0.1% (at the time of rating) 0.05% (1 W:00)
Cross modulation distortion 0.05% (1 W:00)
Power bandwidth 10Hz - 30kHz
Damping factor 80 (8ohms)
Remains noise 0.4mV
Input sensitivity/impedance 1V/60kohm

<Preamplifier section>

Input sensitivity/impedance Phono1 : 2.5mV/50kohm Phono2 : 2.5mV/30, 50, 75kohm High Level Input : 150mV/50kohm
An Output voltage/impedance Pre Out : 1V/1kohm Rec1, 2 : 150mV/1kohm
THD 0.05%
Frequency response Phono(RIAA STD) : 20Hz-20kHz 0.3dB High Level Input : 20Hz-20kHz+0 -0.5 dB
Presence control : 3dB (800 or 2kHz)
Tone control Bass : 10dB (100 or 50Hz) (Turnover 500, 250Hz) Treble : 10dB (10 or 20kHz) (Turnover 2.5, 5kHz)
Filter Low : 15 or 40Hz (12 dB/oct)
High : 9 or 15kHz (12 dB/oct)
Phono allowable input 300mV (distorted [ 0.1% ] 1kHz)
Input conversion noise Phono : -120dB(V)
High Level Input : -100dB(V)

<Synthesis>
Power source AC100V 50Hz/60Hz
Power consumption 130W
Dimensions Width 425x height 148x depth of 387mm
Weight 17kg


[Design Description]

The preceding paragraph direct connection pure contest OCL system has realized high power.
Moreover, about the temperature drift of output end direct-current voltage, the new magnification circuit which shows very few drifts in the large temperature range is adopted. Highly efficient-ization is measured using the part with large current capacity.

The super-low noise transistor developed with the low concentration diffusion technology of the Diatone is adopted as first rank differential amplification.
Compared with the conventional low noise transistor, a 1/f noise of about 2dB is improved, and the dynamic range is also improved.

The pair transistor to which the nakedness characteristic was equal is adopted as a power stage and a driver stage, and distortion at the time of an open-loop is lessened.
The distortion at the time of the Koide power decreased by this, and it has contributed to expansion of a dynamic range.

In order to intercept from a high fever and magnetism which are generated from a power block, it separates clearly and a pre-block is arranged in a front part. Furthermore, it is shielding.
It could maintain at a temperature lower 10 degrees C or more than a power block in the state of anticipated use by this, and the stability of a transistor with a high temperature dependence and the reliability of each part are raised.
The power part and the Puri part are connected with the bottom of both blocks, and have become little design of a secular change etc.

The presence control which can amplify inside compass in broadcloth at a 1dB step is carried.
A change (800Hz and 2000Hz) is possible for center frequency.

A tone control circuit separates a damping time constant circuit, and is considering it as the circuit composition from which a flat frequency response is acquired in the flat position.

The working range where a transistor is linear is wide, and, moreover, tone control amplifier and presence control have adopted amplifier with high stability independently, respectively.

22 contact Attenuator is adopted. Attenuation degree deflection and a gang error is [ the degree of attenuation of 28dB] less than 1.5dB in less than 1dB and the degree of attenuation of 30dB or more.