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Computer Drive New Class A (Technics 1984 HiFi)
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Specifications:
| | | 1. General | | System: | Integrated Transistor Amplifier (New Class A) |
| Colour: 1=Silver, 2=Black: | 1, 2 |
| Power consumption: | 370 W @ 120/240 V |
| | | Pre Amplifier | | Inputs: | Phono MM/MC; Tuner; Tape I+II; Aux/CD/Video |
| Quadro: | no |
| Inp. Sensitivity High Level: | 150 mV |
| Inp. Impedance High Level: | 22 kΩ |
| Frequency Response High Level: | 5-140,000 (-3 dB) HZ |
| Signal/Noise High Level: | 102 (IHF A) db |
| Inp. Sensitivity Phono MM: | 2.5 mV |
| Inp. Impedance Phono MM: | 47 kΩ |
| Frequency Response Phono MM: | RIAA (±0.8 dB) |
| Signal/Noise Phono MM: | 83 (IHF A) db |
| Inp. Sensitivity Phono MC: | 0.2 mV |
| Inp. Impedance Phono MC: | 0.22 kΩ |
| Signal/Noise Phono MC: | 65 (IHF A) db |
| Outputs: | 2 REC OUT |
| | | Equalizer | | Tone Controls: | Bass; Treble |
| Frequencies: | ±10 dB/50 Hz; ±10 dB/20 kHz |
| Filters: | SUBSONIC (-12 dB/oct./30 Hz) |
| Loudness: | 1 |
| | | Power Amplifier | | Speaker Outputs: | 2 x 2 Speakers; Phones |
| Continuous Power 4Ω: | 60 + 60 Watts |
| Continuous power 8Ω: | 60 + 60 Watts |
| Harmonic Distortion: | 0.005 % at rated output |
| | | 2. Physical | | Dimensions in Inches: | 16.93 x 4.29 x 11.42 (w) x (h) x (d) |
| Dimensions in mm: | 430 x 109 x 290 (w) x (h) x (d) |
| Weight in lbs: | 16.8 lbs |
| Weight in Kg: | 7.6 Kg |
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| Reviews |
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Ronaldo Souza - 04/12/2021 
Technics SU-V505 ... recentemente ganhei um V505 , estava com defeito , ele não ligava , só piscava a luz de Stand by , então baixei o manual de serviço e comecei a testar os componentes e descobrir que tenha uns resistores fritados e uns transistores em curto . fiz a substituição dos mesmos e para minha surpresa funcionou .... não sou técnico ... apenas apaixonado por som ... Tenho que reconhecer que o Technics SU-V505 é amplificador de padão Hi-End e Hi-Fi , entrega um audio limpo com graves e agudos bem definidos como eu nuca vi ...para aquele que gosta de ouvir um excelente som esta ai um belíssimo amplificador .... |
Marc Stock - 10/16/2020
The SU-V505 is one of Technics mid range amplifiers from 1983. Offering 60 watts per channel, this is actually one of the more sophisticated amplifiers available throughout all brands during this time.
Technics decided to go for a design where the BIAS control voltage is constantly adjusted in relation to the input signal and temperature of the output transistors. By increasing the BIAS voltage on startup, it offers up a "preheating" stage to bring the transistors up to the 60 degrees centigrade optimum conditions to ensure that the output stage works exactly within the designed parameters and characteristics of the designed circuit, ready for the best possible performance in audio reproduction.
Then a computer-controlled automatic bias micro-controller monitors the output temperature range from cold (60-80 deg c) medium (80-110 deg c) and high (110-130 deg c) and increases or lowers the BIAS voltages accordingly. The reason for this is as transistors heat up, the crossover distortion characteristics change throughout the frequency range and heat range. The Micro-Controller samples this heat information, and adjusts the BIAS 400 times every second to keep the distortion levels to the lowest they can possibly be for any given temperature range. Very advanced stuff even by today's standards.
It also operates the BIAS control voltage in a Class A topology by keeping each transistor active just above its operation threshold for each half of the waveform. So even though it is a PUSH-PULL Class B design, the BIAS circuit forces the transistors to behave more like a Class A design, but this is not your usual A-B circuit either as the BIAS control system is much more advanced and complex, so Technics called it new class A.
This is why you will find the SU-V505 will get VERY HOT and its perfectly normal for it to be so warm you cant even hold your hand over the vents at the top of the unit without discomfort, a drawback for some, but as a result offers up a truly staggering 0.004% total harmonic distortion. Not even modern amps costing thousands can get anywhere near this, typically getting 0.1% and sometimes 0.05%
The only disadvantage of this amp is due to its age, and because it does get so hot naturally it suffers from dry joints, crackly controls, and oxidised relays. The only way round this is to carry out a full strip down, lubricate, and service every 5 or 6 years with examples that have many hours of time behind them, especially if it has spent its life inside a HI-FI cabinet it does tend to cook itself dry with all that heat and built up dust.
It also has a very sophisticated automatically sensing impedance detection circuit, it will detect the exact impedance of your speakers, and automatically select the appropriate power supply tap from the transformer on the input stage. So unlike most amps that are rated at 60 watts for 8 ohms, but will then flood out 120 watts into 4 ohms, the SU-V505 will deliver 60 watts per channel under both 4 and 8 ohm conditions, making it unique in the sense that you cannot melt your transistors when connected to difficult loads, and pushing high volume levels. Its just as well though, when your forcing a class B push pull amp to run class A BIAS control, your already pushing those transistors to the limit of the design scope and by not having a impedance compensating circuit, 4 ohms wouldn't be possible, and they were not going to take a risk on a manual impedance selector switch (as some amps have) either, just imagine the floods of blown transistors on selling these to unsuspecting customers with low-impedance speakers who forgot to change the selector..
My 505 was a cosmetically pristine example, but suffered from all the usual problems and issues above so I had the unit fully stripped down, solder re-flowed, caps replaced, switches lubricated and cleaned, relays de-oxidised and lubricated. Its a good job Technics designed these amps to be serviced and repaired, as you can get the service manuals needed to carry out all the adjustments/overhaul procedures needed to bring it back to its as-new state. I paid for a specialist to do this for me, and its a fantastic sounding amp, at a fraction of the price (even with the overhaul) compared to the sorry excuses for amplifiers you get today..
What is really impressive about this amp though is the build quality. Not a single plastic part or component, everything is made from brushed stainless steel or aluminium, even the knobs and the switches are all made of solid metal, and although is fairly slim, its flipping heavy. The only drawback are the rear speaker terminals, they are the twist-lock type and can be easily broken if you try to put speaker cables that are too thick inside them, so don't use anything thicker than 14-AWG or you will snap them clean off.
Sound quality I would describe it as warm, but very detailed. Its certainly does punch well above its weight in terms of sonic ability. I have the amp connected to a pair of Kef Raymond Cook 104.2's and it really does deliver a sound that is appealing, punchy, and accurate. The bass response is incredible too.
What does the future hold for this little amp? Well I think they are well underrated, only time will tell how they continue to hold up over time. They do require maintenance, you are going to need to keep it serviced and lubricated, it runs hot so you cant coop it up in a cabinet, so its not an amp you can buy, use and forget about. You must respect it, and keep it in good condition, keep it clean, keep the dust away from it, have it serviced every 5 years or so and it will outlast you. Who knows in 20 years time they might be worth a lot more than they are currently. |
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