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Rational Audio Z1

Stereo Integrated Amplifier (1992)

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Rational Audio Z1


Power output: 55 watts per channel into 4Ω (stereo)

Frequency response: 20Hz to 60kHz

Total harmonic distortion: 0.05%

Damping factor: 900

Input sensitivity: 2.8mV (MM), 250mV (line)

Signal to noise ratio: 72dB (MM), 80dB (line)

Output: 400mV (line)

Speaker load impedance: 4Ω (minimum)

Dimensions: 328 x 106 x 200mm

Weight: 4.5kg

Year: 1992



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Reviewed Jun 13th, 2017 by Peter111

Great amp, big sound stage but not as deep as units on hi end of the market. Kickin life in Dynaudio 42 ( a serious load for most of the amps) with no trouble. Krisp and defined treble and reasonable amount of bass. If you get your hands on one, grab it!



sinclair2's picture

re: Z1

AU/RA Z1,Z2,Z3,Z5 - Tesla semiconductors data and world equivalents :

KD711T/KD712T: Uceo/Ucbo=100V, Icm=12A, Pcm=70W, Ft=3MHz, Hfe=15-60
KD606/KD616: Uceo=60V, Ucbo=70V, Icm=10A, Pcm=70W, Ft=2MHz, Hfe=20-100
KD607/KD617: Uceo=80V, Ucbo=90V, Icm=10A, Pcm=70W, Ft=2MHz, Hfe=20-100
KU611: Uceo=50V, Ucbo=60V, Icm=3A, Pcm=10W, Ft=30MHz, Hfe=50-180
KU612: Uceo=80V, Ucbo=120V, Icm=3A, Pcm=10W, Ft=30MHz, Hfe=50-120
KC237V /F is fail/: Uceo=64V, Ucbo=70V, Icm=0,1A, Pcm=0,3W, Ft=150MHz, Hfe=30-150, cbe
KC239F: Uceo=20V, Ucbo=30V, Icm=0,1A, Pcm=0,3W, Ft=150MHz, Hfe=300-900, F=max.2dB /30Hz-15kHz/, cbe
KC239C: dtto KC239F, F=max.4dB /30Hz-15kHz/, cbe
KZ260/16: Zener 1,3W/16V, cathode red strip
KY132/80: standard rectifier diode 0,8A/100V, cathode green strip
KY710: standard power rectifier diode 10A/200V, anode screw

Recommended and tested parts for repair:

KD711T/KD712T: MJE2955/2N3055,2N3773/2N6609 NOS Mot,MJ15015/15016 ONS,2N3716/2N3792 NOS Mot,2N5886/2N5884 ONS,MJ802/MJ4502
KD606 / KD616 used in the manufacture, repair but are not recommended.The best replacement types are original TESLA KD607/KD617 if we manage to buy them.
KU611,KU612: The best replacement is original TESLA KU612, is also an excellent 2N3767,after a minor mechanical treatment works well also MJE15030 ONS.
KC237V: BC546B Philips or ONS, compatible pinning
KC239F: BC550C Philips or ONS, compatible pinning, ONS has less noise /1,5dB!/
KC239C: BC550C Philips or ONS, compatible pinning, I suggest you use ONS
KZ260/16: direct replacement is BZX85C/16 or any better Zener diode 1,3-1,5W/16V
KY132/80: direct replacement is any Si Rect diode,example 1N4001-1N4007 series.
KY710: replacement is any Si Rect power diode 10A/200V in a compatible packaging and in the same connection terminals.

It is highly advisable to replace the original main electrolytic capacitor resources 4.700uF / 63V for high quality snap-in capacitor with a capacity of at least 15.000uF and more, for voltage 75-80V and high allowable ripple current. Reproduction amplifier is greatly improved, residual hum disappears and rises sinusoidal output power up to 15W per channel.

This website is not affiliated with or sponsored by Rational Audio. To purchase Z1 spares or accessories, please contact the company via their website or visit an authorised retailer.