My name is Ralph Stens. I was born in Germany in 1959. At the tender age of 15, I caught the audiophile bacillus and it has never left me since. During my studies — I hold a university degree in electrical engineering, specializing in electronics and high-frequency technology — I began designing my own circuits for my hobby.
Throughout my career, I have primarily designed analog and digital circuits for industrial measurement technology and laboratory applications. Over the years, I have accumulated a wealth of experience in this field. One advantage for my hobby is that the challenges of measurement technology and audiophile circuit design are very similar in many areas.
But then why am I interested in Pass Labs replicas?
From my perspective as a professional electronics designer, the SUSY topology is the best circuit design for audio amplifiers. Over the years, this has been repeatedly confirmed for me through direct listening comparisons on various high-end audio systems. So if there is — at least in my opinion — an optimal amplifier technology, it makes more sense to focus on this circuit design than to attempt to develop something entirely new.
Ultimately, though, the devices I build are never 100% replicas. A company like Pass Labs, for example, is subject to commercial constraints that DIY enthusiasts don’t face. When building one-off units for personal use, you can follow the “all you can design” principle and thus get the most out of the circuits for yourself. In addition, over time, the projects have become increasingly self-contained.
For this reason, this website features descriptions of audio circuits that I designed myself, as well as replicas based on designs by Pass Labs.
Philosophy / Design Guidelines
I am firmly convinced that it takes a certain philosophy — or, to put it more simply, a personal view on technical and acoustic conditions — to build a truly excellent audio system over the years.
If you’re always trying something new, you’ll never stop searching.
I’ve heard the best systems from people who have been studying the subject for decades and have formed their own clear opinions. You can tell that these systems have been gradually optimized over many years.
The best systems are found among DIY enthusiasts.
A statement reportedly made by none other than Dieter Burmester. It also reflects my own experience. This is not because this group of audio enthusiasts is particularly smart, but because what is written above applies to them in a very special way. They cherish and care for their systems and, in most cases, continue to refine them throughout their entire lives.
So what are my design principles? The answer can, of course, be found throughout the entire website, but I’ll try to summarize the key points here. The most important thing, however, is:
These are my rules, and I don’t claim they apply to everyone!
- No dogmatic approach to the selection of active components. You can build excellent devices using vacuum tubes, bipolar transistors, and/or FETs. However, I personally don’t like working with vacuum tubes.
- Symmetrical circuit design is preferable to asymmetrical circuit design. Whenever possible, circuits should be designed to be super-symmetrical.
- I prefer discrete circuits with higher operating voltages to those using integrated operational amplifiers, even though the VV6 and VV8 have impressively demonstrated that this approach isn’t really necessary.
- Even though some of my devices are still designed differently, I now design circuits with full DC coupling of the signal path.
- The power supply for an audio device is at least as important as the actual audio circuitry. Here, too, I prefer discrete regulations to integrated solutions.
- A power supply should always be oversized and able to deliver the required power with ease.
- Whenever it is technically feasible and practical, I build power supplies for stereo applications in a dual-mono configuration. The only compromise I occasionally make is to use a single transformer — usually for space-saving reasons. In such cases, however, I naturally ensure that the secondary windings are separate.
- In mixed systems — that is, systems containing both analog and digital circuitry — the grounds must be kept strictly separate. I only connect the potentials together at the ground terminal.
- As far as I’m concerned, the topic of loudspeakers — at least in the frequency range between 125Hz and 7.5kHz — has been settled since 1980. To this day, I have yet to encounter anything better than the ’57 Stacked Quad, driven by a powerful, super-symmetrical power amplifier. That doesn’t mean, however, that there’s nothing to improve on the speaker.
- Before you start worrying about cables, you should first focus your attention on room acoustics. The improvement you can achieve there is far greater. Most systems in a standard, rectangular living room without any room correction measures are actually not worth listening to seriously. I realize that this statement will rub many people the wrong way, but anyone who has taken the necessary steps knows exactly what I’m talking about here — before 2014, I would have dismissed such claims as pure nonsense.
To support the statement about room acoustics, here is another statement:
Using high-quality speakers in an acoustically untreated room is like driving a sports car across a stubble field.
Dipl.-Ing. Torben Bostelmann (Akustik Module)
That really sums up what I said above!