Welcome back to Tech Talk, recorded in the Best of High End studio with Hans-Ole Vitus, founder of Vitus Audio. In this fifth episode we stay with the engineering and design philosophy behind the Danish brand, but we go deeper into the choices you never see on a spec sheet: why Vitus Audio uses UI-core transformers, how hot a class A amplifier really needs to get, and what happens between a first idea and a finished product. Hans-Ole Vitus also explains why the chassis of a new amplifier can take as much thought as its circuit.
Why Vitus Audio chose UI-core transformers
Many high-end amplifiers rely on toroidal transformers. Vitus Audio went another way and had its UI-core transformers designed by an external specialist. The main reason, Hans-Ole Vitus explains, is how the voltage behaves under load. “When you draw maximum current, the voltage tends to start dropping,” he says. With the UI design, the drop from no load to full load was just 1.5%.
That matters because power depends on the supply rails: if the voltage sags when a demanding loudspeaker asks for current, the amplifier effectively loses power. At the time, Vitus was testing with homemade Apogee loudspeakers that dropped to extremely low impedances, and the difference was easy to hear. “You can hear when an amplifier is not happy with its life, so to speak.”
The choice was not made for size or price. UI-core transformers are big, heavy and expensive. Hans-Ole remembers that buying 50 to 100 pieces for the SM-100 monoblocks cost about as much as a fairly priced power amplifier in a shop, and with today’s metal prices they are probably even more expensive. They also have a drawback: a toroidal transformer passes less noise from the mains to the secondary side. “It’s a little bit give and take,” he says. “From the sound point of view, well, the UI clearly won.”
Class A without cooking
For Hans-Ole Vitus, class A is a big part of what he calls the Vitus sound: a slightly tube-like character from the lower midrange upwards, combined with the control of solid state. “What is super neutral? What’s the reference for super neutral?” he asks. “I would still love to know that.”
Customers often remark that Vitus Audio amplifiers do not run as hot as other class A designs, and that is deliberate. When the EU discussed limiting the surface temperature of consumer electronics, Hans-Ole decided it made sense to design for it anyway, mainly because heat shortens the life of components. Where a very hot class A amplifier might need new capacitors every ten years, he aims for around twenty. A pair of SM-100 monoblocks he picked up in Sweden, 22 years old, still measured the way they should.
Two rules guide the design. The amplifiers should never get more than about 25 degrees Celsius above room temperature, and the amount of class A is set by the core temperature of the output devices rather than by a wattage figure. “At a specific temperature, this is where it kind of just opened up the sound,” he says. Oversized heat sinks keep the temperature at an average of 45 to 50 degrees, where some amplifiers he has owned reached 70 or 80. “You can cook a steak on these things.”
R&D starts with listening
Asked to walk us through a Vitus Audio R&D project, Hans-Ole Vitus starts somewhere unexpected: listening, long before there is a prototype. Listening to distributors, retailers and customers, visiting systems and asking what Vitus could do better. It is a habit from his years at Texas Instruments, when he presented data sheets to engineers and collected their feedback. Around 80 percent of his input comes from the market; the remaining 20 percent is general market research.
Today he speeds up that research with AI, in his own way. Instead of a simple chatbot, he works in Visual Studio Code with GitHub Copilot and version control, so that every change to his documents can be tracked. “This is one of the big problems with AI. It hallucinates a lot,” he says, and version control gives him that control back. For a new product such as the Ri200, he discusses trends and feedback with the system (should an integrated amplifier have HDMI?), turns the result into a project document and then reviews it personally until the specification is frozen. The reason is simple: “While I might think that I have the most brilliant idea for a new product, it might not be brilliant for anyone else than me.”
From schematic to final prototype
Only then does the engineering start. Over the years Vitus Audio has built a library of proven design blocks, such as its discrete op-amp, that can be combined “a little bit like Lego”. Some things are not up for debate: the Reference, Signature and Masterpiece series are fully balanced, and proven input selection circuits are simply reused. After simulation comes the PCB layout and a first proof-of-concept prototype.
The measurements follow a strict order. DC levels first (“if the DC levels are not correct, nothing else matters”), then AC measurements such as gain, then a second prototype with an optimised board layout. Only when the hardware behaves like the simulations does the listening start, and that is where the process can loop for a long time. “They work perfectly. Yeah, but the sound is not good,” Hans-Ole says. Every change sends the design back to the DC and AC measurements until the team agrees that this is it.
The chassis is part of the sound
Next comes the mechanical design, which Hans-Ole Vitus considers just as important. It defines the look, but also how efficiently and consistently a product can be built. He describes it with the Ri200, whose chassis will change compared with the current RI-101. The bottom sheet metal cover of the RI-101 leaves too little room to get your fingers under the unit, and fitting it means sliding the cover in from the back and screwing it from below, a delicate job where the finish is easily scratched. Higher feet would be the easy fix, but they would change the whole look.
So the design, the quotes from suppliers and the assembly sequence go back and forth, with production (Lucas, in this case) closely involved. The SM-025 monoblocks are the benchmark: densely packed, yet well thought out to build. Serviceability counts too, because real life brings lightning damage and, in one case, an air conditioning unit that leaked onto an amplifier. “All these things, it’s much more complex than just the product itself,” he says. Two or three final prototypes are then built and tested for a long period, including their thermal behaviour, before production is signed off.
New models and Mark II versions
A completely new product takes Vitus Audio 18 months or more; the Ri200 is such a project. A Mark II version, like the SM-103, reuses the chassis and changes only the electronics, which takes around nine months. On average, Vitus introduces a new model about every eight years and a Mark II about every four, but only when the electronics alone can lift the performance enough. Some Masterpiece products have run for 15 years without changes, and so has the SIA-025.
Coming up next
That closes episode five of our Tech Talk series with Hans-Ole Vitus. Missed the earlier episodes? Start with Hans-Ole Vitus: From Drummer to Designer, then Measurements Serve the Music, The Pursuit of the Absolute and Rethinking the Rules. Discover the Reference, Signature and Masterpiece series on the Vitus Audio website, and listen to this episode as a podcast on Spotify.
