Analysis of Shengya SV-221 Amplifier

Not long ago, when I paired a friend with a set of pure music-use audio, I selected Shengya's SV-221 gallstone mixed power amplifier as an amplifier, and I had the opportunity to listen to the characteristics of Shengya amplifier again, and made a simple analysis of it. . Now I will introduce some experience of the power amplifier to my friends.
The panel design, button layout and three-piece block cover and radiator cover of Shengya's SV-221 is a very regular design. Of course, it still maintains the combination of Shengya's integrated power amplifier Appearance style.
The SV-221 power amplifier is very different from the common gallstone mixed power amplifier. It is not the structure of the anterior gallbladder and the posterior stone, but 12AU7 and 6N15 double transistors are used to form the differential input stage of the front stage and the rear stage electron tube, that is to say, the electron tube, the transistor and the field effect tube are used to form a voltage amplification circuit. This may be the first in the domestic Hi-Fi amplifier circuit design. It can also be said that the circuit design of the existing various amplification components including the op amp is brought to the extreme. The second amplification stage immediately following the differential input stage of the tube is still a compound differential amplification of the first-stage field effect tube and the triode. In addition, the power amplifier adopts direct coupling from beginning to end, which improves the extension of the high and low frequencies to a certain extent. Generally, the extension of the high and low ends of the tube amplification circuit is slightly worse, so the direct coupling method can make up for this deficiency, but it needs to increase the DC servo circuit. As a merging machine, DC correction circuits are designed in the front and back stages. In order to improve the distortion of the current output stage and deal with the speakers of various impedances, the SV-221 uses three pairs of Toshiba A1941 / C5198 power tubes per channel and is driven by the three-stage Darlington composite tube. As expected by the SV-221 designers, this amplifier has no problem driving low-impedance, even "large food" speakers, especially when driving heavy-load speakers, it can show the outstanding characteristics of this amplifier. Like many high-end Hi-Fi power amplifiers, this power amplifier also uses the front high and low front. The entire voltage amplification is powered by the positive and negative 60V of the Class A voltage regulator, and the current level voltage is positive and negative 50V, so it can cope with large dynamics. Music and provide low distortion indicators. Later, it was learned from the manufacturer's information that this SV-221 circuit was actually the SA-31 / SP-331 before and after the split of the SA-31 / SP-331, which won the "most praised" title of the expert group at the second domestic audio-visual equipment exhibition. The circuit used by the power amplifier.
In general, SV-221 is also quite good in the selection of components. For the power transformer, a "tall" 500W ring cow with small magnetic leakage and small internal resistance is used. The voltage amplification stages of the front stage and the back stage are powered by Class A power supply. The whole machine adopts Japanese nichicon filter capacitor, the total capacity is more than 4200 microfarads. It can be seen from the output power parameters provided later that the power supply equipment and current output capability of the power amplifier are strong. The output power of a general power amplifier under a 4Ω load is difficult to reach twice the output power under an 8Ω load. There are not only the factors of insufficient power supply design, but also the lack of output power of the post-stage power tube. The sound source switch adopts the step switch to switch the board nearby. The volume potentiometer is a relatively expensive ALPS blue plastic case with guaranteed quality. All resistors use metal film five-color ring high-precision type. The small internal capacitors are all high-grade low-loss CBB capacitors.
It should be noted that although the internal process of the SV-221 power amplifier does not seem to be completely satisfactory, its structural layout is indeed worth mentioning. The whole chassis is a frame structure, each unit is placed in a relatively independent part, the interior is divided into pre-stage, power supply, left and right power amplification and other parts, and the parts that are easily interfered, such as signal input terminals, tone adjustment, etc., have been further improved In accordance with the requirements of the national certification of the Great Wall of electrical products, the AC power supply has been well isolated and protected. Since the tube circuit is more susceptible to interference, although the structure is more complicated, it seems to be necessary. The overall mass distribution is more symmetrical and even. The two high-power radiators are distributed on the left and right sides of the chassis, and the heat dissipation effect is better. Moreover, the radiator is closed with a fine radiator cover, which will not endanger the use Personal safety is of course much more beautiful than exposing the radiator. For the convenience of after-sales maintenance, the bottom plate is designed to be separable, so that the motorcycle and maintenance do not need to be disassembled.
The function button configuration of SV-221 takes into account the needs of audio enthusiasts of all levels. The power amplifier is equipped with equal loudness switch, tone through switch, two groups of speaker output terminal switch and EQ connector. For example, the two sets of output terminal switching switches are for the convenience of audiophiles to connect two sets of speakers at the same time for A, B comparison audition or playing two-wire crossover configuration; EQ connector is convenient to use the amplifier as a pure pre-stage or pure post-stage. It should be noted that although the SV-221 uses a gallstone hybrid structure, and the volume potentiometer is placed at the input end of the power amplifier, it is found that the signal-to-noise ratio is still very high in use, which may be attributed to the machine's "complex" Structural design, if the technical indicators provided by the manufacturer's manual are not high, the signal-to-noise ratio is only 90dB, which also shows the reality of Shengya. 8Ω load output 100W power, 4Ω can output 200W power, also shows that this power amplifier has a powerful power configuration and driving ability, provides a more relaxed premise for the selection of some low-efficiency speakers.
The main technical parameters of SV-221 are as follows: (1) Frequency response: 20Hz ～ 20kHz (-0.5dB); (2) Signal-to-noise ratio: 90dB; (3) Distortion: 0.1% (1kHz, 1W); (4) Output power: 100W (8Ω), 200W (4Ω). var check_allow = "/d/Api/iscantalk.html"; var add_url = '/ d / article / write /'; function CheckLogin () {now_uid = ''; var ElecfansApi_checklogin = '/ webapi / passport / checklogin'; var logout_url = "{: U ('Login / logout')}"; var logout_url = 'http://bbs.elecfans.com/member.php?mod=logging&action=logout&refer=front'; $ .get (ElecfansApi_checklogin, function (data, textStatus) {if (data! = "") {EchoLoginInfo (data); CheckEmailInfo (data); data = $ .parseJSON (data); now_uid = data.uid; / * var login_content = 'write an article