In the world of Hi-Fi audio, we often come across situations that look more like scams than genuine opportunities. This was the case of a customer who, eager to find affordable solutions for his audio system, ended up dealing with yet another “basement builder” selling poorly assembled tube amplifiers. Trying to save money, he ultimately bought a jumble of devices with terrible results and a total cost far higher than that of a properly designed and built product.

This story is not just the sad account of a deceived customer, but also an opportunity for a creative recovery that turns disappointment into joy. With the “Merlòtto” project, a Hi-Fi tube amplifier based on 6V6 tubes, I managed to give new life to two devices that had been discarded as electronic waste. For me, recovering these contraptions is much more than a job — it’s a true act of craftsmanship and a source of fun. Disassembling and analyzing each component, salvaging reusable parts, and reassembling everything into a design that embodies what the original should have been from the start is a stimulating and rewarding challenge.

This process not only restores value to components that would otherwise end up in a landfill, but also promotes a more ecological and sustainable approach. Every recovered piece helps reduce environmental impact, preventing semi-new components from being thrown away. “Merlòtto” is not just an amplifier — it’s proof that with passion and creativity, what seemed destined for the scrap heap can be transformed into a high-quality product, made at lower cost through smart reuse and artisanal skill. In this article, I’ll present the results of this project, showing how an idea can evolve from a recycling challenge into an achievement of excellence in the world of high-fidelity audio.

Overview of the Starting Units: A Journey Through Restoration

Before presenting the single-ended 6V6 “Merlòtto” amplifier, it’s important to look at the original units that were used for parts recovery. These abandoned devices, once deemed useless, became the foundation of a project that transformed discarded material into a high-quality piece of craftsmanship.

The two units I used as the base for “Merlòtto” were originally sold illegally as low-cost audio solutions, but their actual quality was beyond classification. Despite being built with new components, their assembly was poor and the performance so miserable that they could barely be called functional. The first unit was marketed as a preamplifier equipped with 1626 tubes.

A nearly comical description presented it like this: Configured as a small power amplifier with a double triode input stage and a single-ended 1626 triode output driving a WE transformer. All filament supplies are DC with large capacitors… to prevent core saturation, the transformers are loaded through a large 5 uF capacitor of absolute quality.

As if a transformer could stop saturating just because of a fancy WE capacitor… “Wè Wè!”… Measured, the unit had a frequency response of 90 Hz to 10 kHz at –1 dB, plus a poor EZ41 rectifier tube that had to charge 1800 uF of electrolytics at every power-on, risking a miniature atomic blast each time. The second unit disassembled was advertised as a single-ended power amplifier using AL4 or WE38 tubes.

Measured, the second device proudly delivered a staggering 0.12 W RMS before clipping. Beyond that, the waveform turned into a chopped half-wave, producing a fuzz effect that even the most experimental guitarists wouldn’t dare use. And let’s not forget the tiny transformer heroically trying to charge two huge electrolytic bottles at every startup. The first time I powered it on, it made such an epic noise that I immediately pulled my hand back, fearing electrocution or an impromptu fireworks show inside the tubes.

Another Wreck with UY76 Tubes

The danger of misinformation and disappointment: The problem isn’t just financial. These trash amplifiers also discourage newcomers from exploring the world of tube audio. The spread of ideas like “tube gear sounds bad” or “they’re all poorly made” harms not only honest and skilled builders but also the public, who risk missing the chance to experience the true joy of tube sound. Moreover, those who find these devices “pleasant” often lack the experience, trained ear, or reference systems necessary to make a fair judgment. Without comparing them to truly good amplifiers, it’s impossible to realize how little value these products actually have — often not even worth their modest asking price.

Let’s Dismantle Everything!

This phase of the project is one of my favorites, reminiscent of childhood days spent gleefully taking apart Lego houses like a curious little explorer. Each time I open one of these devices, it feels like discovering hidden treasure among mountains of electronic junk. During the teardown, it’s often surprising to find genuine gems among the scrap — quality capacitors, gold-plated RCA connectors, tube sockets, valves, and even sturdy brackets.

The following photos show several moments of this demolition process. Every recovered component is carefully examined to determine whether it can be reused in the new project. Some of the salvaged parts were integrated into the “Merlòtto” amplifier, while others, which were not useful, were traded to lower the customer’s cost. Finally, what couldn’t be reused or had no remaining value was properly disposed of.

This process not only gives new life to components otherwise destined for the landfill, but also makes the entire amplifier-building journey exciting and deeply satisfying.

The Reconstruction Begins!

Now that the salvaged material has been sorted, it’s time to start the reconstruction phase. I decided to reuse one of the wooden chassis, even though it wasn’t high quality, because it had an interesting shape. It was made from simple conifer plywood — an ordinary material that the original tinkerer had tried to “beautify” with walnut stain and some sort of glossy finish.

The result, unfortunately, only emphasized the wood’s natural ugliness instead of hiding it. Still, the frame offered a solid base for my project. Rather than trying to enhance such mediocre wood, I chose to conceal it and use its shape as the foundation for “Merlòtto.” With a bit of ingenuity and creativity, I turned this element into a key part of the rebuild. In this initial phase, I was helped by Rita Stefani, who stripped off the old varnish and patched up the unnecessary holes.

Next, I designed the front control panel, which I decided to make using 3D resin printing.

I made the aluminum panels using a traditional manual approach.

Here’s the RCA socket plate: the three close pairs are dedicated to inputs, while the wider pair is a low-level audio output designed to drive a subwoofer, as requested by the customer. All the gold-plated RCA connectors were recovered from that 1626 preamplifier.

These photos show the process of creating the front mask, also 3D printed in resin. The volume potentiometer was recovered from the original units, while the three push buttons used to select the inputs are NOS parts I had in stock. It’s important to note that the audio signal doesn’t pass through these buttons. Instead, they control high-quality signal relays with silver contacts sealed in an inert atmosphere. This approach avoids the use of cheap bronze rotary switches, which tend to oxidize and degrade the signal over time.

The next photos come directly from Rita Stefani’s workshop, where she finished the chassis after I had prepared the space for the new circuit.

Now I am posting a series of photos that document the assembly of the actual circuit. In these images you can see how I shielded the wooden chassis with copper, a crucial step both to protect the circuit from possible electrical interference and to ensure electrical safety. The photos show the various steps during assembly, from the initial stage to the final tuning. During this last stage, I disconnected some components to carry out tests and replacements, making sure to achieve a perfect result for the power supply section and the feedback circuit.

The red capacitors and the tube sockets were salvaged from the starting materials.

Technical Description of the Merlòtto Amplifier

The “Merlòtto” amplifier is a single ended power stage designed with particular attention to circuit quality and efficiency. It uses 6V6G or 6V6GT tubes for amplification, with a 6SL7 driver tube that feeds the circuit. For rectification I chose a 5V4G tube, supported by a CLC cell filter with small value capacitors, specifically sized for the capabilities of the chosen rectifier tube.

The filament supply is AC, a detail that clearly contrasts with the claims of the builder of the starting units, who boasted the use of huge capacitors and DC filament supplies. That configuration was not only pointless, it was sometimes harmful, and it showed a clear inability to manage hum and other issues on his part.

Inside the amplifier there is an ECC82 tube, configured as an active low pass filter. This part of the circuit is designed to produce the signal needed to drive an external subwoofer amplifier. The signal for this function is taken from the speaker output posts, so it does not interfere with the main input signal.

All transformers used are new and made by SB-LAB. The output transformers are the SE8K5-6V6P models, while the choke is a 15S56 rated 10 H and 100 mA. In addition, a custom 24S90 power transformer was used, built to meet the specific circuit needs of the Merlòtto project.

The “Merlòtto” amplifier delivers 3.4 watts RMS per channel before clipping, with a damping factor of 4.9 and a frequency response from 15 Hz to 35 kHz with an attenuation of ?1 dB. Total harmonic distortion is limited to 0.5% at 1 watt.

The “Merlòtto” project is also available as a premium version. Anyone who wants to buy the transformer set and the schematic to build the DIY amplifier can simply contact me. I will be happy to provide all the details needed to complete the project.

Below you will find the usual graphs that show the performance.

Bandwidth @ 1 Watt

THD

Square Wave 100 Hz

Square Wave 1 kHz

Square Wave 10 kHz

Frequency Response of the Subwoofer Output

Cost Considerations

Building “Merlòtto” required 33 hours of work, not including the extra hours dedicated to fine tuning and tests, which took an additional full day. I will also need to invest further time to produce the documentation required to legally sell the amplifier. During construction I reused some components such as the tube sockets, the chassis, some capacitors, the RCA posts, the volume potentiometer, and the 6V6 tubes already owned by the customer. However, most of the components, including the transformer set, the sheet metal, and all the other internal parts, as well as painting costs, were purchased new.

The total cost was well over one thousand euros. This figure might seem high, but consider this. Is it really advantageous to buy those “contraptions” sold on subito.it for 400 to 600 euros? By purchasing two preamplifiers and one power amp, the customer spent almost €1600 on questionable quality equipment that did nothing but collect dust as electronic “garbage”.

There was a saying from our grandparents. “Buy cheap, pay twice”.