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Tensai TP 2500 hifi pre-amp


 

General:

Simple build Tensai pre-amplifier made in Japan in the1980's.

Front ^

Special features:

All properties a simple high-end pre-amp should have are in this design.

 

Specifications:

Tensai TP 2500.
Output voltage: 1 Volt per channel at ~ 4K Ohm.

Frequency range: 15 - 25,000 Hz (+/- 1.0 dB)
Harmonic distortion: less than 0.004%
Intermodulation distortion: less than 0.01%
Signal-to-noise ratio: >105 dB
Crosstalk damping: >65 dB
Treble control: +/- 10dB at 20kHz
Bass control: +/- 10dB at 50 Hz
Loudness control: at 100 Hz + 10dB and at 10kHz + 3dB
Noise & rumble filter: -6dB / octave
Input sensitivity @ 1kHz and maximum output:
         Record player DIN: 2,5mV @ 47k Ohm.

         Tape A: 150mV @ 80k Ohm.

         Tape B: 150mV @ 80k Ohm.

         Tuner: 150mV @ 80k Ohm.

         Tape monitor: 150mV @ 80k Ohm.
         MC input: 0,2 mV @ 100 Ohm.

Output impedance: headphones 600 Ohm.
Power supply: 220/250 volts 5W max.
Dimensions: 80 x 250 x 430 mm.

 

 

Interior  ^

 

User Manual:

Click here to download the A&T 1984 review in PDF format in Dutch.

 

Schematic:

Click here to download the service manual of the Tensai TP 2500

This quite simple pre-amp consists basically of a MC fet/IC amp with a output IC amp in bothe channels.

The outputs are relay switched that is very convenient.

Click here to download the schematic diagram of the TP2500

 

Modifications:

To get a fine high quality pre-amp you have to do little upgrading, the power supply is noticeable simple.

The used electronic parts are of good quality, but aging is an issue so some parts should be replaced.

Specially the electrolytic
power supply caps are not best quality, the blue main caps:
C007 and C008, 2x 1000µF or 1500µF are the better choice, also you may get a softer startup when switched on.
Power supply
R003 resistor of 1K ohms - 1 Watts, should be replaced by a 5 Watts capable R, to keep things safe.
All
Blue electrolytic-caps should be checked and replaced if out of specs, the Orange LL el-caps are usually fine.

The MC phono input can be adjusted by resistor value to your specific MC cartridge impedance within approx 50%.

Since this is
not a DC-coupled electronic design, the coupling caps between the 2 main stages (in L and R)
should be of much better quality, the
Wima MKT 3,3 or 4,7 µF 63V cap is very usable for C419 and C420.
Do
not use big sized HiVolt capacitors: keep them as small as possible, no tantallum and not parallel multi cap.

Set the transformer from 220V~ to 230 or 240 in Europe if possible, due to the
detrimental voltage rise from 220V to 240V~.

The schematic diagram provided by Tensai has some errors in the schematic and mistakes in component listing.
 

Broken PCB solderside with damage to the power supply by bad handling of  DHL post shipping company ^

 

Backpanel ^

Phono MC stage ^

 

Tone section ^

 

Sound:

The sound of the restored Tensai TP 2500 is very good.

 

 

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© PE1MMK Hans Hilberink last update:  22-09-2019.