Sony TA - 5650 VFet Integrated Amplifier - Serviced / Preventive Update Installed
Item History & Price
| Reference Number: Avaluer:29704891 | Model: TA-5650 |
| Type: Integrated Amplifier | Country/Region of Manufacture: Japan |
| Brand: Sony |
Legendary V-Fet Sony Integrated Amplifier TA-5650 serviced / upgraded
V-Fets or Vertical Fets are special Junction Field Effect Power transistors produced during 1970- 1980 period mainly by Sony/ Yamaha and small extent NEC. These were precursor to MOSFet or Metal Oxide Semiconductors. V-Fets have a very desirable Drain current characteristics like Vacuum Tube Triode and very linear transfer character for low distortion amplification. Amplifiers made with V-Fets are are sought ...after even today due to their exceptional Sound reproduction- a very pleasing tonal character unlike any Solid state amplifiers. from my own listening, i consider them to be some times unique mid range response.
Since V-Fets were expensive to produce and cheaper MOSFets took over the Power Electronics arena, Sony and Yamaha stopped producing these devices and Amplifiers made using these devices. These old V-Fet Amplifiers are still sought after due to their inherent Sound characteristics. One has to listen to such amplifiers to understand the craze for these. I have more than 5 amplifiers with me.
Sony's stash of these amplifiers need special attention to upgrade if they have survived so long as many Sony amplifiers failed suddenly due to certain components of that era were in these. The failing components are not V-Fets as V-Fets are rugged devices but such failure can cause doom to V-Fet output transistors. These V-Fets are not available as spares any more This information is well documented in many audio DIY sites like Audiokarma/ DIYAudio etc. Also the repair or maintenance of these equipment is not easy unlike many solid state amplifiers due to the requirement of Gate bias before applying Drain Source Voltages. So one cannot use slow AC voltage application using Auto former as it will destroy these V-Fets.
The listed amplifier is the third TA-5650 I worked on and it is one of the later updated version from Sony with Sony factory updates for reliability as in their Service bulletin. Sony realized that these models were failing due to certain design factors and corrected them in their later models. This unit is a modified unit. So my work was limited to replacing all those failure prone Diodes and Power supply upgrade to avoid Voltage Doubler circuit failure due to unbalanced load. I also adjusted the Bias to match latest Sony Service notes to these amplifiers and the amplifier runs cooler. Both Service bulletin Mods are in this Unit. Along with those Sony recommended updates, Diodes were replaced with modern reliable double diodes.
You are buying an Amplifier after all the necessary updates to prevent failures and you can expect years of use without worrying. Since internally, it is showing great condition of all components and behaves well during actual use, i did not go to replacing all Capacitors etc. This one unit sounds beautiful by directly using the Power Amp as there is a provision to directly connect your source provided the source has Volume control. However all the inputs/ preamp controls work including Phono ( MM input).
Please ask questions before bidding. This item is bit heavy and I will take adequate care to pack this for safe shipping
International Buyers - please check with me for actual shipping charge before bidding
Excerpts from Nelson Pass ( Pass Labs) article on Sony V-Fet-----------------------------------This is about audio power amplifiers, more specifically about those made with aspecial type of transistor known originally as a VFET, now more commonlyreferred to as a Static Induction Transistor (SIT).In the 1960's silicon power transistors began to replace tubes in audio poweramplifiers, being more convenient in a number of ways. The transistorsthemselves were smaller, less costly, more efficient and they needed lessexternal hardware to make them work.There were some complaints about their sonic performance in audio amplifiersas compared to tubes, and some efforts were made to give transistors a more“Triode-like” character.(1) Similar efforts and discussions about them continue tothis day.In 1972 a U.S. patent application was filed by Junichi Nishizawa describing aspecial type of JFET (Junction Field Effect Transistor) where the “drain-currentto drain-voltage characteristic simulates the anode-current to anode-voltagecharacteristic of the triode vacuum tube very closely.” (2)Examples of “VFETs” were produced by Sony and Yamaha forty years ago andappeared in power amplifiers produced from about 1975 through 1980(3). Theseamplifiers are now prized for their exceptional sound, the credit popularly goingto the linearity of the VFETs(4). They were called VFETs at the time becausethey have a vertical (not lateral) structure. The subsequent invention anddominance of vertical MOSFETs (Metal Oxide Semiconductor Field EffectTransistor) made use of the term confusing, so now they are generally referredto as Static Induction Transistors (SIT), except perhaps as reference to theseoriginal parts.These transistors were also exceptionally fast as switches, and in 1976 Sonyalso produced an early version of the Class D audio amplifier, the TA-N88.(5)(6)By the 1980's Sony and Yamaha ceased production of VFET amplifiers. Variousreasons for this have been offered, the most likely being that production of theseexotic parts was considered too expensive to compete with the cheaper verticalMOSFETs which appeared on the market.
V-Fets or Vertical Fets are special Junction Field Effect Power transistors produced during 1970- 1980 period mainly by Sony/ Yamaha and small extent NEC. These were precursor to MOSFet or Metal Oxide Semiconductors. V-Fets have a very desirable Drain current characteristics like Vacuum Tube Triode and very linear transfer character for low distortion amplification. Amplifiers made with V-Fets are are sought ...after even today due to their exceptional Sound reproduction- a very pleasing tonal character unlike any Solid state amplifiers. from my own listening, i consider them to be some times unique mid range response.
Since V-Fets were expensive to produce and cheaper MOSFets took over the Power Electronics arena, Sony and Yamaha stopped producing these devices and Amplifiers made using these devices. These old V-Fet Amplifiers are still sought after due to their inherent Sound characteristics. One has to listen to such amplifiers to understand the craze for these. I have more than 5 amplifiers with me.
Sony's stash of these amplifiers need special attention to upgrade if they have survived so long as many Sony amplifiers failed suddenly due to certain components of that era were in these. The failing components are not V-Fets as V-Fets are rugged devices but such failure can cause doom to V-Fet output transistors. These V-Fets are not available as spares any more This information is well documented in many audio DIY sites like Audiokarma/ DIYAudio etc. Also the repair or maintenance of these equipment is not easy unlike many solid state amplifiers due to the requirement of Gate bias before applying Drain Source Voltages. So one cannot use slow AC voltage application using Auto former as it will destroy these V-Fets.
The listed amplifier is the third TA-5650 I worked on and it is one of the later updated version from Sony with Sony factory updates for reliability as in their Service bulletin. Sony realized that these models were failing due to certain design factors and corrected them in their later models. This unit is a modified unit. So my work was limited to replacing all those failure prone Diodes and Power supply upgrade to avoid Voltage Doubler circuit failure due to unbalanced load. I also adjusted the Bias to match latest Sony Service notes to these amplifiers and the amplifier runs cooler. Both Service bulletin Mods are in this Unit. Along with those Sony recommended updates, Diodes were replaced with modern reliable double diodes.
You are buying an Amplifier after all the necessary updates to prevent failures and you can expect years of use without worrying. Since internally, it is showing great condition of all components and behaves well during actual use, i did not go to replacing all Capacitors etc. This one unit sounds beautiful by directly using the Power Amp as there is a provision to directly connect your source provided the source has Volume control. However all the inputs/ preamp controls work including Phono ( MM input).
Please ask questions before bidding. This item is bit heavy and I will take adequate care to pack this for safe shipping
International Buyers - please check with me for actual shipping charge before bidding
Excerpts from Nelson Pass ( Pass Labs) article on Sony V-Fet-----------------------------------This is about audio power amplifiers, more specifically about those made with aspecial type of transistor known originally as a VFET, now more commonlyreferred to as a Static Induction Transistor (SIT).In the 1960's silicon power transistors began to replace tubes in audio poweramplifiers, being more convenient in a number of ways. The transistorsthemselves were smaller, less costly, more efficient and they needed lessexternal hardware to make them work.There were some complaints about their sonic performance in audio amplifiersas compared to tubes, and some efforts were made to give transistors a more“Triode-like” character.(1) Similar efforts and discussions about them continue tothis day.In 1972 a U.S. patent application was filed by Junichi Nishizawa describing aspecial type of JFET (Junction Field Effect Transistor) where the “drain-currentto drain-voltage characteristic simulates the anode-current to anode-voltagecharacteristic of the triode vacuum tube very closely.” (2)Examples of “VFETs” were produced by Sony and Yamaha forty years ago andappeared in power amplifiers produced from about 1975 through 1980(3). Theseamplifiers are now prized for their exceptional sound, the credit popularly goingto the linearity of the VFETs(4). They were called VFETs at the time becausethey have a vertical (not lateral) structure. The subsequent invention anddominance of vertical MOSFETs (Metal Oxide Semiconductor Field EffectTransistor) made use of the term confusing, so now they are generally referredto as Static Induction Transistors (SIT), except perhaps as reference to theseoriginal parts.These transistors were also exceptionally fast as switches, and in 1976 Sonyalso produced an early version of the Class D audio amplifier, the TA-N88.(5)(6)By the 1980's Sony and Yamaha ceased production of VFET amplifiers. Variousreasons for this have been offered, the most likely being that production of theseexotic parts was considered too expensive to compete with the cheaper verticalMOSFETs which appeared on the market.
