Uniting source components with power amplifiers, it must perform the critical functions of impedance matching, level balancing and volume control while maintaining perfect signal accuracy and channel integrity. Adding nothing. Taking nothing away. While the perfect pre-amplifier continues to be a technical challenge for audio designers, we believe the 525 pre-amplifier gets closest to the ideal.
Perfect volume control
The 525 pre-amplifier owes much to the design of the range-topping soulution 725 Pre-amplifier. It uses the same volume control which ingeniously combines the smooth fingertip control of variable resistors with the precision and stability of fixed resistor networks. For the 525 we’ve chosen the best performing Vishay Dale resistors with relays of the utmost quality. The end result is volume control that is finely adjustable in 95 steps of 1 dB each, with no perceptible switching clicks. Truly the best of both worlds.
Input selection too uses very high-quality relays. The design – which switches ground as well as signal connections – ensures that only the selected input is connected through to the 525 electronics, the remainder being isolated. By buffering all signals immediately after the input, the 525 pre-amplifier presents only a minimal load to source devices. Both balanced and unbalanced inputs are available.
As few components as possible in the signal path speak for an unbalanced circuit concept. In this case, the lowest possible stereo conversations can only be achieved with a consequent dual-mono design. The analogue circuits and the associated power supplies of the left and right channels are physically separated from one another and are additionally decoupled with filter networks.
Level and phase correct with all loads
An ideal pre-amplifier like the 525 pre-amplifier maintains perfect level accuracy and phase accuracy regardless of load. But measured values are only part of the story. Ultimate sound quality should always be the first priority. At no time should distortion, noise or hum be allowed to colour the music.
In order to drive the longest of signal cables, the output stage of a pre-amplifier must be sufficiently powerful to do the job. The 525 pre-amplifier employs a powerful, very fast and ultra-wide (2 MHz/– 3 dB) output stage that can drive long cables with ease. We team that with a similarly robust, high specification switched-mode power supply which features high-precision and extremely low-noise linear control circuits. Backed by more than 400,000 μF of storage, the power supply of the 525 provides virtually unlimited pulse power with indiscernible levels of noise.
Musical transparency is pre-eminent in the 525. Colouration is simply not a factor. Control too is at the 525’s heart: stereo imaging precision is exemplary while sound sources appear perfectly focused on the sound stage. Once you audition the 525 pre-amplifier you will come to understand the true nature of sound and the importance of the right pre-amplifier in achieving it.