Hand-craft Cutting-edge High End Audio

Riviera Audio

PS AUDIO
Stellar Series

Technical overview

Truly Unique Tube Amplifiers

by Luca Chiomenti

I presented my first design for industrial production to the public about 25 years ago. In the introduction I wrote: “We believe that, in the last 20 years, high fidelity has ended up in a blind alley. There is a pointless race to technical perfection. For too much time the final goal seemed to be to reach the limits of measuring instruments. This choice seemed to have forgotten the real function of an audio amplifier: to reproduce the music through an electroacoustic transducer.”

25 years later the situation appeared even more confused. Today, there is a general agreement that the commonly used tests for audio frequency amplifiers do not correlate with the audio quality. Audiophiles largely reject technical specifications and bench tests as an indicator of the subjective sound quality. Nevertheless, perfect bench tests seem to be essential for any product on the market.

I cannot synthesize over 25 years of (my personal) study and research on the relation between subjective experience and laboratory measurements. I based my studies on direct experiments and hundreds of pages of bibliography covering over 80 years. I hope to complete a white paper on this argument soon. Now I will try to give some focal points that are the foundation for the Riviera design.

We must go back to the beginning. An audio amplifier must reproduce a signal with the highest fidelity… for the human ear, not for instruments. This is the point.

It is critical:

1) to understand some aspects of the functioning of the human earing system and, consequently

2) to define the characteristics of the reproduced signal for the human ear, not for an electronic measuring system.

Let’s start from the ear.

  • When we ear a pure tone, many studies have verified the creation of harmonics inside the ear and, specifically, in the cochlea. This is not a new discovery. First reports on this distortion are from Fletcher (yes, the famous of the Fletcher-Munson curve, in the ‘20s); more precise reports came from H.F. Olson (Acoustics, 1947) and many others later. It is interesting to observe that the ear generates really high levels of second harmonic: about 10% for pressure levels of 90dB (not 120dB, 90dB!). Higher order harmonics levels decrease with the order of harmonics. We can define a spectrum of the harmonic distortion of the ear. The shape of harmonic distribution is very important: there is high predominance of lower order harmonics, with a decreasing spectrum. This spectrum changes with the pressure level but this point is too complex to examine here. The key points are: 1) the high level of distortion the ear self generates; 2) the ear+brain system cancel those harmonics and the perception is that of an absolutely pure tone. In other words, the hearing system suppresses the harmonics generated by itself. Interesting, isn’t it? Even more interesting is this: the system suppresses the sound of “that” range of harmonics even if they are of “external “ origin, under the condition that the shape, the pattern, is maintained. Quite obvious: the system is programmed to cancel that shape of distortion and it cannot distinguish whether the origin of the distortion is internal or external (some interesting musical phenomena are related to this behavior, i.e. the missing fundamental note). If the harmonics differs from this pattern shape, the ear+brain system detects the harmonics as different tones. Based on this, we think that an amplifier generating a distortion spectrum similar to that of human ear will result extremely transparent and clean, even if its THD level is relatively high.
  • The above mentioned mechanism is dependent on the pressure level. In synthesis, the higher the pressure level, the higher the harmonics distortion that our ear generates (and accepts). This brings us to prefer amplifiers with distortion monotonically increasing with the output power.
  • The higher the pressure, the higher the order of harmonics that ear generates. This means that, at higher levels, an increased quantity of higher order harmonics can be accepted.
  • The detectable distortion depends, among other things, on: 1) the ratio between the peak and the average value of the signal; 2) the duration of each signal peak. Studies have proved that distortion can even reach very high values and still remains inaudible if the peak length is very short.
  • Masking is the well-known phenomenon where a low level tone in close proximity to a higher level one is not audible. This can limit the influence of IM distortion in an amplifier with a predominance of low order harmonics. This effect seems to be even higher if the distortion spectrum shape of the amplifier is close to the ear’s one.
  • Feedback is the classical method used to reduce THD and upgrade circuit performances (THD, IMD, bandwidth, noise and more). Unfortunately feedback reduces the lower order harmonics (less harmful and more “benign” for the ear) much more than the higher order harmonics. More and better: high levels of feedback act as a generator and “multiplier” of higher order harmonics (harmonics that ear detects as “dissonant” and noisy). Even if these high order harmonics are under the audibility level, the mechanism generates a “noise floor” that seems to be absolutely undesirable for the human ear. All this suggest to avoid feedback (specially overall feedback) or to try to reduce its use to the minimum.

Starting from this theoretical base, we defined the ideal characteristics for “human ear dedicated” amplifiers. Riviera amplifiers are optimized for the bench test that demonstrated an actual relation with the listening experience only, careless of pure technical virtuosity. We focused on the following points.

  • Optimization of distortion for amplitude and frequency: THD does not need to be extremely low, but it must absolutely follow the human ear distortion shape. This means predominance of lower order harmonics, with their regular distribution in frequency (the higher the order, the lower the harmonic level, with a relation between harmonics similar to the human ear one). Furthermore, the distortion level must be monotonically increasing with power level. The amp should have a soft clipping and, if possible, the distortion spectrum must be similar to the ear spectrum even in this area (or to the higher level possible before losing the right shape).
  • The use of Zero Overall Feedback and minimum level of local feedback, to minimize the above mentioned negative effect that this technique has on sound result. This is the best way to reach the desired distortion behavior.
  • A good open loop BW.
  • A reasonable DF, like in best tube amplifiers: between 15 to 20, without looking for useless records. This point also contributes to provide articulation and harmonics richness in the low frequencies.
  • Total stability on every load.
  • Absence of protection, to avoid their negative effects on sound and dynamics.
  • Extreme care to the power supply.

These theoretical points are then implemented in a real amplifier design.

Here the way we implemented these points.

  • The Zero Overall Feedback and the minimum use of local feedback, when absolutely indispensable, is the first solution to reach the desired distortion behavior.
  • The use of the A class in all stages is the logical consequence: we need to have the maximum linearity without “tricks”.
  • The hybrid solution is the next logical consequence: the triode is the best voltage amplifier and, mostly in a s.e. configuration, it offers a “natural” distortion shape, very close to the required one. Silicon devices (and specially Mosfets) are the best choice to handle power and low impedances; if properly used and driven, they can offer a good distortion shape too. In the topology adopted they also give the desired output impedance.
  • Protection circuits damage sound. In our thinking this is a fact. So… no protection circuits (only fuses on PSU rails). Consequently a real large dimensioning, not for appearance (coke-like capacitors…) but in the real key points (PSU, transformers, power devices). A secondary consequence is the need for an adequate mechanical dimensioning too.
  • Accurate PSU design. 2 transformers and 5 separate PSU. The tube PSU is PI-filtered and stabilized (with a MOSFet); in the audio power PSU stage there is a PI filter too and the distributed capacitance: instead of 2 big-and-slow capacitors, many little-and-fast capacitors, with the last ones extremely close to each power device.
  • There was a long and accurate musical and bench optimization (with continuous shift from the bench to the listening room and vice versa).
  • Mechanical and “physical” manufacturing with a quality level of a laboratory instrument and a made in Italy design.

BEAUTIFUL AESTHETICS

TAILORED FOR LONG LISTENING SESSIONS

A core belief of Meze Audio is to create products that last through years and years of industry changes, bringing long-lasting value to the customer. Elite is no different.

From looks to technology, this headphone was designed to surpass all short-living trends and become a true heirloom.

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Stellar Phono Circuit explained

Riviera Audio Laboratories Electronics, Meyer Tonapparate Loudspeakers, Tone Imports, RMAF 2018

PS Audio engineer Darren Myers shares the secrets of design in the new Stellar Phono Stage, a 700 part all discrete all FET design that's never been attempted before. Extraordinary noise levels and remarkable sound quality is in store for vinyl lovers. Find out how it was done.

Industry Reviews

About

RIVIERA

Riviera Audio Laboratories s.r.l. was founded in January 2017: it aims to produce innovative quality products for the highest end of the audio market.

Riviera has brought together the complementary skills of three members to produce audio components aimed at bringing new advances in analogue sound, merging passion, technology and innovation.

First and foremost, Luca Chiomenti is the company’s audio designer and engineer. He has been designing and manufacturing Hi-Fi systems since the 1990s, combining both technical expertise and craftsmanship which now find their expression in Riviera products.

Silvio Delfino deals with imports and exports. He has tried and tested experience in global marketing and sales in the field of Italian audio high end. He now turns his considerable expertise to Riviera.

Marco Muzio is an expert in industrial design and rendering for mechanical applications; he brings to Riviera his outstanding skills to chassis design and manufacturing.

Riviera is the future to be heard in analogue.

Frequently Questions Asked

Do you ship for free anywhere in Australia?

HeyNow Hi-Fi ships products all over Australia. The cost of shipping is free no matter what it is or where it’s going. HeyNow Hi-Fi uses an efficient and agile business model and therefore can afford the cost of shipping without increasing its prices to compensate or by charging you an additional fee to get the product to you.

Can I pick my purchase up from the shop?

Yes, you can pick up your purchase from the showroom in St Kilda in Melbourne or my warehouse. However, this is done only through prior request. I have selected stock in my warehouse but often have stock stored by the Australian Distributor and therefore I must have them release the stock first and ship it to me.

Do you match competitor’s prices?

The answer is yes. HeyNow Hi-Fi does match competitor’s prices. I’m happy to do so and won’t make you jump through hoops to make a purchase. There are many reasons why you would like a price matched. Sometimes a competitor has left a pre-price rise price on their website. You may not connect so well with the competitor who has a cheaper price. The competitor may have been rude or pushy and put you off. You may have a great relationship with HeyNow Hi-Fi and like the way we treat you. You may be buying other items with your order and would like to buy it all from one place. You may like to shop locally, and we are your nearest dealer. HeyNow Hi-fi may have the product in stock and the other shop doesn’t. You may like my photo and video on the website and want to buy from me. I have offered you great service and advice, but someone else has the item listed lower. Please let me know and I will be very happy to help you.

Is the price on the website the best price?

The price on the website is the retail price or the Australian distributor’s advertised sale price. HeyNow Hi-Fi displays retail pricing so you can see the value of the product. Under every product and on the top banner of the website is a button to click to get a discount code. This discount code is yours for every purchase you make in store and online. – keep it somewhere safe. If you have seen a better price advertised or offered, please get in touch as we do match Australian competitors’ prices and still offer free shipping. If you want to offer me a price, please feel free to ask as at worst I will refuse – but if you don’t ask you won’t know.

Do you have everything listed in your website in stock?

This website is much an online shop as it is a catalogue of possibilities for you to read, appreciate, do some research, educate yourself, compare and of course purchase from. With the myriad of possibilities and options available in this sector it is impossible for anyone to keep everything in stock. I work very closely with the Australian Distributors of all products listed and will do whatever I can to get your chosen item to you as quickly as possible. Often products are in stock but sometimes they are on a plane or boat coming to us. Sometimes, however the order needs to be generated for you. I am here to help and to pressure the distributor to get it as quickly as they can for you. I will keep you updated and request the fastest route to get it here for you. When something is out of stock with one reseller or two, it is often the case that it is just not in the country. Therefore, you need to choose someone to be in your court to get it promptly and manage your order. HeyNow Hi- Fi is here to do that for you.

I am concerned about overseas parity pricing

So am I! I want the best deal for my clients and customers. I think that if the pricing model that a distributor or manufacturer uses doesn’t work for global sales then they need to negotiate harder before choosing to import a product. We live a long way from the rest of the world and therefore there are considerations to contemplate before you come up with your final price from an overseas retailer. Firstly, there is the cost of shipping, which has gone up considerably thanks to additional global demand for consumer items and the ships and planes are at a premium and charging accordingly. Next the pricing in the US never includes TAX. This is always added at point of sale and is always an additional charge when shopping in the US. The US works on state taxes which means the tax can vary dramatically from state to state up to approximately 15%. The next consideration is warranty and therefore the issue of the local distributor who has made no money from your transaction and is not interested or obliged to fix your faulty overseas purchase. This is obviously a risk you can take in an educated manner some things have less risk of failure than others and all products come into Australia with no warranty – this is added by the distributor as it’s their risk – this does have a financial cost to protect you. Australia has some of the best consumer protections in the world.

Next is the insurance liability of shipping these products around the world. Manufacturers and Distributors have ways to pack containers with product and safety mechanisms in place when they airfreight sensitive parcels, unlike an opportunistic retailer with a cheap price overseas price, who may send it cheaply and as you’re trying to save a couple of hundred may not pay for freight insurance and then you’re stuck – this is another factor on the cost of reaching our parity figure.

Next is customs and GST. When you import anything above the threshold, the Australian government wants their pound of flesh. You must pay for customs clearance and GST on your purchase – yes you may think there are ways around this but, not if you get caught...

So, with all these considerations in place HeyNow Hi-Fi does all it can to offer products that come as close to overseas parity pricing as we can. If you think you like a product, which has a cheaper retail price overseas than here, please reach out to me and I will see what can be done to help you to buy it locally and with the full support of the Australian distributor.

You have a lot of brands on your website...

Yes, I do. And I intend to grow my portfolio too. The reason for this is that you, the consumer, the music lover, will have spent a lot of time reading reviews and working out what you are interested in. Then you can call your regular Hi-Fi store who probably knows less about what you’re interested in than you do, because you’ve watched every YouTube clip and read every review about it; but they have a special on something they’ve got in stock or which they believe is right for you, or maybe they don’t know anything about the upcoming game changing product you’ve dedicated every night before bed for a fortnight reading about, and then they try to talk you out of it, talking about reliability or poor sound or paid reviewers getting a kickback.

I respect your time and research as well as your desire to try something new or different and am as excited about the next new product rather than the brand we’ve sold for the last 40years. I’m as excited to hear about how it works in your system as you are too. I love new toys and never want to miss out on the next great technology, I also want you to have a place where we learn together. I have over 30years experience in the Hi-Fi industry and have sold some of the most amazing new technologies – The first Philips wide screen 32inch TV in 1991, Laser Disc players in 1988, the first Sony PS1 in 1993 with ridge racer on a rear projection TV, the first Fujitsu Plasmas PDS4201 in 1997 and the first Sonos Systems nearly 20 years ago. I must be open to new technology – this can only happen by having as many amazing brands as possible on my website and available to you. I listen, I play. I understand and I consult with my experts to be able to offer you useful and helpful advice.

My goal is to offer you unbiased advice on Australia’s largest range of high-performance Hi-Fi, Home theatre and all the accessories and ideas that go with it.

What is the warranty on your products?

HeyNow Hi-Fi purchases all its stock from the authorised distributors. They determine the warranty period, terms and conditions. We have tried where possible to provide warranty length on each product page as a quick reference. All products also come with a warranty card in the box as provided and created by the supplier. Some of these documents are very official and stern. HeyNow Hi-Fi’s role in your potential warranty claim is to make this a more personalised and understanding process. If you have a warranty claim the best thing to do is email hello@heynowhifi.com.au with the details of the issue. Please note that adding a contact number makes communication much easier. Depending on what the issue is we will suggest a few troubleshooting ideas, understanding: of course, that you will have tried many ideas before contacting us so we will probably just suggest what you’ve already tried. From there we can work out numerous solutions to get your product fixed quickly, including sending you to the repairer with it, get you to ship it to our warehouse or to the distributor, or sending out a service technician. Note that shipping, transportation costs and installation are not covered by warranty. Unless of course the issue is an installation issue as a result of our installing your system in which case you are covered .

We will get your product fixed a quickly as possible, bearing in mind that all repairers are third party to us and we have no control over their schedules and parts availability. HeyNow Hi-Fi’s role is to make you as comfortable as possible and hopefully keep the music playing in your house while your product is being repaired.

How do I get a quote and advice from HeyNow Hi-Fi?

The best way to get advice from us is to call me, on either 0415668307 or 03 95250022.

You can also email me on geoff@heynowhifi.com.au , please do include a contact phone number as it is much easier for me to call you back and advise you than sending back and forth emails in the hope that I’m offering you the advice you need.

If you just want a price or price match the easiest way is to call me or text me through the icon at the bottom right of the website. Just copy and paste the link from my website for the item you are interested in and simply ask what price or ask me to match a price. Unlike many of my competitors I am happy for you to tell me the price you want – I can say yes or no.

If you want a quote on a system, please outline what you’re hoping to achieve, provide enough detail so I understand the scope of the works. Let me know where you are geographically and importantly again, please provide a contact number. I can learn a lot more about how to help you in a phone call than trying to put an email quote back to you without conversation.

Please remember there is only one Geoff, and I am trying to help a lot of people, I have a great team around me – including Australia’s best audio distributors, my amazing installation team and my incredible website and administration team. We can absolutely build the system of your dreams; we just need to work together.

Can you design a home theatre system for me?

Yes! I have many years’ experience in this sector f the market. I understand all the technologies of surround sound, HDMI. 4K, HDR etc. I work with the best leading brands of surround sound AV receivers, disc players and streamers, speakers, screen and projectors and televisions.

I can design your room, your acoustics, the step for your second row of seats, the blinds, even the lights. My team can work with your builder to do as much or as little as you want us to.

We can provide you with a programmed control system with a remote or iPad or better still, both. The control can operate the whole audio/ visual system, the lights, lower the blinds as well as make your home secure with cameras and alarm systems which can be monitored remotely.

I personally love home theatre and enjoy watching movies and on demand TV shows as often as I can. I favour many genres including Sci-Fi, Drama, comedy, Horror, action and but certainly not limited to effects laden blockbusters. I love a good story and great acting and really appreciate the artform.

I want you to get the maximum excitement for the money spent. I think that some of the component parts of a Home theatre system are technological rather than performance based and therefore within a budget – If there is one. – There are some things you’ll keep forever and others that should be changed to keep up with technology – highlighting those areas can save unnecessary costs and compromises. Talk to me about your home theatre desires, I’m sure together we can make a great movie space in your home.