by Luca Chiomenti

There are many reasons why Riviera preamplifiers can be considered different from all others. The main reason is that everything in these devices has been optimised for the musical result and not (only) the technical result. This optimisation has involved many more aspects than are normally taken into account in typical preamplifier designs. Among the theoretical points common to all Riviera designs, the following are particularly significant for preamplifiers.

• Optimisation of amplitude and frequency distortion: THD must be minimal but above all it must have an optimised trend with respect to the distortion present in the human ear. This means a predominance of low-order harmonics, with a regular frequency distribution and with the distortion level monotonically increasing as a function of output. Even at high output levels, the circuit must exhibit a distortion spectrum with a shape as close as possible to that of the distortion found in the ear to limit the negative effects.
• Zero Overall Feedback and as little local feedback as possible, to limit the negative effects this technique introduces on the sound result. I consider this to be the best way to achieve the desired behaviour in terms of distortion.
• A good bandwidth even in open loop.
• Maximum attention must be paid to the power supply section, intended not only as a (large) dimensioning, but above all it must be considered that the power supply is included in the signal path and must therefore behave like an audio circuit, i.e. it must ‘play’.

The circuit that handles the signal is entirely tube-based, pure Class A and Zero Feedback. It is a circuit that combines extreme technical performance with exceptional musical results. It is an SRPP designed and optimised to provide distortion with an ‘aural’ distribution of harmonics, a feature common to all Riviera designs and which makes it absolutely transparent to the human ear. No form of feedback is used to achieve this. Optimisation involved many aspects: the working point of the active devices, the choice of the best mix for the passive components, the mechanical structure and more.

All of our products use oversized linear, not switching, power supplies. The power transformers are far more substantial than those that are used in typical preamplifiers. The key point, however, is this: since the power supply is also part of the signal, it must be designed like an audio circuit. In fact, our power supplies were developed with the musical result in mind, using unusual and elegant solutions. Filtering is always realised with double pigreco filters, in some cases resistive, in others inductive. The anode power supply is stabilised with unconventional circuits. Altogether there are at least 5 separate stabilised supplies in our preamplifiers (in some units there are more).

The inputs are always true balanced and are almost always made with very high quality transformers, with a mumetal core and external mumetal shielding.

The volume control employs motorised potentiometers of the highest quality (on some devices they are exclusive custom parts), elastically mounted on the chassis to prevent the transmission of vibrations. The signal path from the input to the potentiometer is minimised, which is why the potentiometer is often mounted away from the front panel and connected with a brass bar and gimbal.

The balance control is realised with potentiometers or resistive dividers mounted on the output and not on the input. This makes it possible to avoid the two potentiometers in cascade at the input (volume and balance, as is normally the case), as I believe this solution is responsible for a significant degradation of the sound result.

Only one capacitor is present on the signal. Since there is no single component that is perfectly neutral, I created a mix of various capacitors of different technologies, selected and optimised for the best sound result in each device.

When present, the balanced output is designed using custom transformers of exceptional quality. Since I believe these components contribute to a reference result, they were also used on the unbalanced output. This ensures that the results offered by the balanced and unbalanced output are absolutely equal.

The chassis. We have always believed that the mechanical behaviour of a device, particularly a preamplifier, has a significant influence on the overall sound result. That is why extreme care has been taken with the mechanical part of the devices: this is another aspect of the overall optimisation. All units use chassis parts machined from solid aluminum.

Finally, it must be made clear that when we refer to listening evaluations and the optimisation of the sound result, we do not focus on just one aspect of the result (the best resolution, the highest dynamics, the greatest impact, the deepest bass, the fastest speed and so on). If we take one design aspect to extremes, we do so to the detriment of the overall balance: thus we end up losing the music and musicality. The ultimate goal is to achieve the best balance between all the parameters of reproduction, as each one is important in music.

The goal of each Riviera product is to reproduce music as naturally as possible, as in a live concert.