Vincent SV-500 Amplifier
Hybrid circuits have been known for a long time, but nowadays, as a rule, they are used in high-end amplifiers, where the character of the sound is more important than the cost. The cost of such amplifiers is higher, mainly due to the complexity of the power supply - the tubes will not work without heating and high anode voltage, which must be filtered well.
The question is why do developers meet such inconveniences? The fact is that the tubes can significantly expand the dynamic and frequency ranges, and this is achieved without the introduction of deep feedback. And the path is shorter. Tubes perfectly increase the voltage, but to co-ordinate with the load, you need an output transformer - an expensive and large-sized element. But in hybrid amplifiers it is not needed, because the output stage is built on transistors, which are perfectly consistent directly with the load.
This is exactly what is done in Vincent SV-500 amplifier, which the manufacturer positions as a more affordable version of the popular SV-227. After the volume control the input signal is fed to the double triode 12AX7 - a low-noise tube with high gain. It is necessary to compensate for the losses introduced by the tone controls, which correct the nature of sound at low and high frequencies. If the loudspeakers and the room do not need this, the equalizer can be excluded from the audio path by pressing a button on the front panel. The next stage on 6N1 has an increased load capacity and transmits a signal to the input of a transistor power amplifier. Judging by the type of the printed circuit board, this is a classic circuit operating in AB class. 100-watt A1941/C5198 transistors are mounted on aluminum heat sinks. Power is supplied from a toroidal transformer located in a shielding compartment. The amplifier's output power is 2x50 W for a load of 8 Ohms and 2x80 W for 4 Ohms.
Switching of inputs is implemented on a miniature relay and is designed to connect six sources - four linear analog and two digital optical and coaxial interfaces. There is also a pair of linear outputs - fixed for recording and adjustable. Accordingly, Vincent SV-500 can be used as a tube preamplifier or as an external DAC in conjunction with a CD transport. The built-in DAC is built on a PCM5100 chip that supports resolutions up to 32 bit/384 kHz.
Listening took place in a spacious room. All components matched the amplifier in terms of class and price: Vincent CD-S1.2 CD player and Piega Classic 5.0 2.5-way floor-standing speakers.
An important parameter indicating the quality of an amplifier is its ability to control acoustics. With insufficient damping the bass loses clarity, becomes echoing, and if it is too large, it becomes dried and lifeless. Judging by the nature of the lower band, SV-500 has optimum damping: both single kicks and fast series are transmitted precisely, with a sharp attack. On drum set recordings, the drum and the working drums sound lively, with smoothly damped diaphragm vibrations. You hear the vibrations of the deck when double bass in the jazz quartet plays, its sound is rich and velvety.
The upper band is correct too. Even with the fast and bright AMT tweeters the sound did not have the excessive contrast characteristic of low-cost transistor amplifiers. In some recordings, string overtones may seem overly rigid, but such nuances are easily eliminated by selecting cables. In general, the upper spectrum is airy and transparent, with no hint of a veil.
Another important parameter of the amplifier is the independence of the sound character from the volume level, i.e. the constancy of the spectrum of harmonics with different power output. When you increase the volume in Vincent SV-500, neither color nor sharpness appears at high frequencies. The overall tonal balance is not disturbed, the music sounds as comfortable as at low volume.
