Ancestrum Lux, when something serious is born from scrap! The story of Ancestrum Lux begins the way many SB-LAB adventures begin: with a customer arriving carrying a pile of junk passed off as handcrafted Hi-End equipment by some misunderstood genius. After opening them up, the term “scrap” seemed considerably more appropriate than “Hi-End”.

They were the usual devices described as “super natural”, “transparent” and “musical”. A description that, in the world of creative audiophilia, often successfully replaces any measurement or engineering competence. Listening tests, however, suggested a slightly different conclusion. And a far less flattering one.

One characteristic shared by many of these unpresentables is the presence of large mirror-polished copper or brass panels. To be fair, aesthetics are often the only thing their builders are capable of conceiving. When electronic knowledge approaches zero, there is always the polishing machine. And if one really wants to complete the masterpiece, the classic motor-run capacitors carefully spray-painted black cannot be missing, because in basement-level Hi-End even an industrial component worth a few euros can magically become “audio grade”.

Among the various landfill relics there were two monoblocks based on 801A tubes. Enormous transformers, completely oversized, probably unsuitable for the tube itself, to the point that they could barely deliver 1 watt. Naturally, they were monoblocks. Why? Because in the audiophile world there is a myth that separating the two channels into two distinct chassis magically improves stereo separation.

Monoblocks have only one real advantage: they allow the weight to be distributed. If we are talking about a pair of KT88 power amplifiers with large transformers and generous power supplies, where a stereo amplifier could easily reach 35 or 40 kilograms, splitting it into two chassis makes perfect sense. When instead we are discussing amplifiers delivering barely one watt per channel that, assembled into a single stereo chassis, would perhaps weigh five kilograms, the whole story about “channel separation” belongs more to audiophile folklore than engineering. If two channels interfere with each other inside an amplifier of this type, the problem is not that they share the same enclosure. The problem is that whoever designed or built it did not know how to do the job properly.

Fortunately, the two chassis were identical and, most importantly, built from reusable materials. Perfect candidates for a classic SB-LAB recycling operation. I therefore completely dismantled both amplifiers, recovering all reusable materials together with numerous components taken from other devices delivered by the same person. From this scrap emerged a stereo amplifier divided into two separate chassis: one dedicated to the power supply and one dedicated to the audio section. The choice was not dictated by fanciful audiophile theories about channel separation, but by the need to keep the power transformer as far away as possible from the interstage transformers. The two chassis are therefore connected through a dedicated multipolar cable.

From this demolition came Ancestrum Lux. The name derives from two elements. The first is the presence of 801A tubes, thoriated-tungsten filament triodes known for their characteristic intense glow. The second is the circuit philosophy adopted, strongly inspired by amplifiers from the 1920s and 1930s.

Ancestrum Lux is in fact a completely zero-feedback design, based on interstage transformer coupling and with all bias voltages derived from a single resistive divider inserted in series with the center tap of the high-voltage secondary winding. A solution that would probably make many modern designers faint today, but which was perfectly normal at the time.

The circuit uses a 5R4GY rectifier, an unavoidable choice considering the plate voltages exceed 500V. The input stage is entrusted to 76 tubes. The 76 is a triode introduced in the early 1940s as a universal tube for amplification, oscillators and detectors. It is a simple, linear tube and very pleasant to use in low-level voltage stages.

The 76 tubes drive a pair of 1626s. The 1626 was originally developed as a high-power RF oscillator for military applications. It was not designed for audio use but, as often happens, some tubes created for other purposes proved to be excellent in completely different fields. In Ancestrum Lux, the 1626s operate as an intermediate power stage, providing all the energy required to properly drive the interstage transformers.

Finally, we reach the undisputed stars of the show: the 801A tubes. The 801A is the evolution of the famous 10Y and probably represents one of the finest thoriated-tungsten filament triodes ever produced. Thanks to its extremely linear plate curves, it can operate with very low distortion levels even without any assistance from feedback. Compared to the original 10Y, it offers a higher plate dissipation rating of 20 watts.

Like all directly heated filament tubes, it requires special attention to filament supply design, because any shortcut immediately becomes audible. In the photograph below I was fine-tuning the filament power supply circuit.

All transformers used are custom SB-LAB models. After dismantling the original equipment, the longest part of the work began. Hidden beneath a generous layer of black spray paint was a beautiful walnut veneer that deserved to be preserved. The paint was completely removed, and the many unnecessary holes present on the rear panel were closed.

Custom decorations were then created through laser engraving and wood staining. Once preparation was completed, the chassis received a traditional shellac finish. For final assembly, I built new metal panels which were subsequently professionally painted.

Some mechanical adaptations were produced using 3D resin printing.

In the end, a large quantity of components from the original equipment found a new life inside a project finally worthy of the name.

The final measured performance is:

• Maximum power: 3.6W
• Undistorted power: 2.8W
• Damping factor: 1.7
• THD at 1W: 0.9%

Observing the frequency response reveals an interesting detail. The output transformer deliberately exhibits approximately 1dB attenuation at 50Hz. No, this is not a mistake. It is entirely intentional. Zero-feedback amplifiers with a low damping factor naturally tend to produce bloated, slow and poorly controlled bass. Many Hi-End manufacturers fight the problem in exactly the same way, deliberately limiting low-frequency response. The difference is that almost nobody will ever admit it.

Having repaired, modified and measured hundreds of amplifiers over the years, I can say that I have encountered this solution far more often than many people imagine. In Ancestrum Lux this choice was made openly and consciously. A slight controlled attenuation is preferable to artificially inflated and uncontrolled bass. Even the shape of the 10kHz square wave perfectly reflects the nature of the design. After all, the signal passes through no fewer than two transformers along the audio path. Expecting solid-state amplifier performance would simply mean not understanding what is being observed.

From a sonic perspective, Ancestrum Lux possesses all the classic characteristics of zero-feedback amplifiers. The sound is open, airy and endowed with a remarkable sense of depth and three-dimensionality. These are qualities many enthusiasts deliberately seek and which contributed to the legendary reputation of classic triode circuits.

These characteristics do not appear out of thin air. Like every engineering decision, the absence of feedback carries a precise sonic signature. Ancestrum Lux was not designed to pursue absolute fidelity or a reproduction rigorously identical to the original signal, but rather to enhance those particular tonal nuances that make classic triode amplifiers so fascinating.

This does not mean the result is less enjoyable, quite the opposite. It simply means that the goal of the project is not to disappear completely from the audio chain, but to offer a musical presentation with its own personality. It is precisely this personality, made up of harmonics, spaciousness and perceived naturalness, that continues to attract many enthusiasts to zero-feedback circuits even today.

For this reason, it finds its ideal match with full-range drivers, acoustic-suspension systems and high-efficiency horn loudspeakers. Like all zero-feedback amplifiers with a low damping factor, it is not the ideal choice for bass-reflex loudspeakers that depend heavily on electrical control of the driver at low frequencies.

The nature of the project should also be considered when choosing musical material. Ancestrum Lux is built around a historic circuit topology, free of feedback and characterized by a very low damping factor. For this reason, it is not the most suitable amplifier for reproducing particularly complex, densely layered music with large dynamic swings and numerous overlapping instruments. Expecting this kind of performance from a few-watt single-ended zero-feedback amplifier would simply mean asking it to perform a task it was never designed for.

Where Ancestrum Lux truly excels is with small acoustic ensembles, jazz, vocal music, blues, chamber music and, more generally, all genres in which tonal naturalness, soundstage reconstruction and microdynamics are more important than sheer impact and sound pressure. In these contexts it delivers an engaging and highly captivating listening experience, perfectly consistent with the philosophy of the great triode amplifiers of the past.

Ancestrum Lux was born from a pile of junk equipment. And perhaps that is its most interesting aspect. It demonstrates that even the worst audiophile scrap can become something worthwhile, provided there is a serious design behind it, a few decades of experience, and above all the determination to place engineering ahead of legends.