LDC-26/ALBATROS — a transportable analog tube listening instrument (prototype development)

[Halicarnassus]

Hello everyone,

My name is Mehmet Cengiz Yılmaz and I am writing from Istanbul, Türkiye.

I have been involved with music and analog audio systems for many decades. In 1968 I received the “Best Composition” award in the Turkish High School Music Competition with my song Zazie. Since then, my listening life has been shaped by vintage radios, tape recorders, tube amplifiers and long-term analog systems.

Recently I started developing a small project that I call LDC-26.

The idea is not simply another headphone amplifier but what I describe as a transportable analog listening instrument.

The concept focuses on deliberate listening rather than portability alone.
Some conceptual directions of the project:
• tube-based voltage stage
• relay stepped volume control
• separation of analog and digital sections
• intentional power architecture instead of pocket-size constraints
• tactile interaction with the device
At the moment the analog module is under construction with a master technician here in Türkiye. The goal is to complete the analog stage first and later integrate the rest of the electronics into a working prototype.

I am sharing the concept here mainly to receive feedback from technically oriented listeners and engineers.
Photos below show some of the devices that influenced my listening philosophy over the decades.

Thank you for reading.
Halicarnassus

 

[Halicarnassus]

Imagination and Intuition come before Knowledge and Experience.
- Mehmet Cengiz YILMAZ


LDC-26 / ALBATROS
A Transportable Analog-Hybrid Instrument

Friends,

I am putting this project out in the open because I have grown tired of the way serious audio is so often wrapped in mystique, inflated language, and price mythology.

LDC-26 / ALBATROS is not being shown here as a finished legend, and not as one more boutique object asking to be admired from a distance.

It is a live project. It has a direction, it has a body, and it has some very real engineering questions still attached to it.

The present format being worked around is 220 × 280 × 100 mm, with a projected full-load weight of around 2.6 kg. The current direction combines a 5654 / 6AK5 input stage, an EL84 Class-A output stage, an isolated step-up high-voltage rail in the 250V range, internal 3S battery operation, an external secondary battery magazine concept, and support for a 15V–19V external adapter. The intended input side includes USB-C, optical, coaxial, analog RCA, and high-gain Bluetooth. The output side includes 3.5 mm, 4.4 mm Pentaconn, 6.35 mm headphone out, fixed RCA line out, and variable RCA pre-out. Control is centered around a 64-step relay attenuator, input selection, and gain management.

That is the shape of it as it stands now.

I am not posting this as mythology. I am posting it because I think projects like this should sometimes be opened before they are polished into something false.

The attached PDF is not a brochure. It is an open technical note. It shows what the machine is trying to be, where the difficult parts are, and which decisions still need to be earned properly on the bench.

That is intentional.

This is my way of pushing back against the old habit of hiding **real engineering** behind luxury fog.

So this thread is also a call.

I would like to hear from builders, tube people, transformer people, layout-minded designers, battery-path thinkers, and anyone who still values technical honesty more than showroom language.

If something here looks weak, say it.
If something can be improved, say how.
If an assumption looks risky, point to it.
If a decision looks promising, explain why.

Criticism is welcome.
Corrections are welcome.
Alternative approaches are welcome.
Warnings are welcome.
Solidarity is welcome too.

The point is not applause.

The point is to put a living design in the open and let serious people test it, question it, and sharpen it.

That is why LDC-26 / ALBATROS is here in public view now.

Respectfully,
Mehmet Cengiz Yılmaz

For those who want to look beyond the words, the open technical note is attached below as a PDF.

 

[Halicarnassus]

LDC-26 / ALBATROS — An Invitation

This instrument was designed for people who actually listen to music.
For decades, there has been an asymmetry between desktop performance and portable listening — and nobody building portable devices has seriously tried to close it. LDC-26 / ALBATROS is built around closing it.

Analog warmth and harmonic texture, in the same architecture as modern digital sources. Four separate expensive devices, replaced by one instrument that fits in a bag.
The category is transportable instrument. That is a different thing.
Now the real point.

If you are reading this, you have probably spent too much money on this hobby, or held yourself back from spending it, or been stuck somewhere between the two. LDC-26 / ALBATROS has an answer: your money can stay in your pocket. One quarter the market cost for the same performance — because the architecture is open, the design is open, the code is open.
No secrets. No mysticism. No commercial interest.

You can build your own companion instrument alone, or with others. The technical dossier is here — every circuit decision, every operating point, every unresolved question included. We listed the unresolved questions because this is not a marketing document. There are real engineering problems still open, and this community can answer them.

There is a good path to walk together.
This is an invitation to those who want to walk it.

Mehmet Cengiz Yılmaz — HALICARNASSOS
Istanbul

 

[Halicarnassus]

Hello again,

To follow up on the invitation and vision shared above, the LDC-26 / ALBATROS has now officially reached the "Build-Freeze" stage. We have translated the intuition into a finalized engineering dossier to ensure objective performance matches the analog soul of the instrument.

Final Engineering Highlights:

• B+ Power Path: A specialized 120 kHz Flyback Converter designed for minimal ripple (<5mV target) and high-speed transient delivery.
• Power Integrity: LTC4412 Ideal-Diode management with a 3S Samsung 21700 array, ensuring rock-solid DC stability.
• Impedance Optimization: Custom transformer taps for 32/64/300 Ohm to maintain optimal damping factors across different transducers.
• Thermal Control: Integrated Zoning Strategy within the 5052-H32 Aluminum chassis to isolate the radiant heat of the EL84s.

I have attached the Complete Engineering Package (Rev. AU3-R) below. This document includes our full validation protocols and schematics. I would appreciate any technical feedback from the community regarding the grounding and ripple mitigation strategies as we move into physical prototyping.

 

[Halicarnassus]

LDC-26 ALBATROS – Signal Architecture, Output Strategy & Power Topology

A quick hand-drawn overview of the current LDC-26 ALBATROS architecture.
(Concept sketch – signal integrity zoning, output strategy & PSU separation)

This sketch reflects the current design direction of the LDC-26 ALBATROS concept, focusing on clarity, modularity and real-world usability in both desktop and transportable scenarios.

Signal Path:
- Multi-input structure (DAC / CD / AUX)
- Input selection stage with short signal routing
- 64-step relay-based attenuator
- Tube gain stage (low-noise, musical character)
- Discrete output stage for headphone / line driving

Output Strategy:
- Dedicated Line-Out (fixed level)
- Variable Pre-Out (post gain & attenuator)
→ Allows integration with external amplifiers or active speakers

Connectivity:
- External RP-SMA Bluetooth antenna
→ Improves wireless reception and placement flexibility in practical desktop use

Power Topology:
- Separated analog supply architecture
- Rectification + multi-stage filtering
- Regulated low-noise rails for sensitive stages
→ Designed to preserve micro-detail and spatial integrity

Design Philosophy:
This is not a feature-packed device approach.

It is a signal integrity-first architecture:
- Short paths
- Clear zoning
- Minimal interference between stages

The goal is simple:
To create a transportable, ritual-oriented listening instrument
that preserves the emotional and spatial truth of music.

Feedback is very welcome.

 

[Halicarnassus]

A small additional clarification:

The analog section is already in progress, and the current work continues toward a first complete module.

At this stage, I am simply placing more emphasis on the tube gain stage as the foundation of the overall architecture.

For a hybrid system like this, ensuring a stable and convincing analog core first still seems to be the most reliable path forward.

I would be interested to hear if others approach similar designs in the same way.

 

[Halicarnassus]

One final note:

The project is intended to evolve in a transparent manner, with technical documentation shared once the architecture reaches a stable state.

If this direction resonates with anyone involved in serious technical or manufacturing work, I would be open to continuing the discussion at a deeper level.

 

[kemmler3D]

Hi Mehmet, looks like a really interesting project. I appreciate the idea behind creating a more tactile and intentional way to listen to music - as we all know, digital and streaming and smartphones make music convenient, but perhaps too much of a commodity. Paintings command more attention when hung in a gallery vs. flashed on a smartphone screen, after all.

I do not have any engineering ability to contribute, but just wanted to say hello and good luck with the design and build.

 

[Halicarnassus]

Hi, thank you — I really appreciate this.

You described exactly the starting point of this project.

Convenience has made music accessible, but at the same time it has also flattened the experience.
The intention here is to bring back a sense of presence, control and physical connection to listening.

Not by going backwards, but by re-centering the system around a strong analog core.

Let’s see where it goes.

Mehmet Cengiz YILMAZ

 

[Halicarnassus]

A short technical note related to this sketch:

1. JFET Gate Reference
Add 1MΩ to AGND to stabilize bias and startup behavior.

2. Headroom
Verify interaction between tube swing and 12V rail on bench.

3. Output Strategy
Define stage as line-level buffer; add separate headphone stage.

4. Heater Referencing
Elevate heater relative to cathode to reduce hum.

5. Power Filtering
Use enhanced filtering beyond simple RC for HV boost noise.

Status: Transition from conceptual to build-oriented design.

 

[Halicarnassus]

Working on the analog side of a hybrid tube / solid-state headphone amplifier concept.

Right now I’m trying to keep the discussion focused on a few practical points before building further:

– adding a DC reference to the JFET gate
– checking headroom between the tube stage and a 12V buffer rail
– separating line-level buffering from actual headphone drive
– keeping heater reference and grounding under control for noise

I wrote the attached note by hand just to keep the idea clear and practical.

Curious how others here have approached the headroom side in similar hybrid stages.

Mehmet Cengiz Yılmaz

 

[Halicarnassus]

Small build update.

The amp is running now, but there is still some noise there.
Grounding may be part of it, still trying to pin that down.

I’m also still moving a few things around the tube section, so the layout is not final yet.

Posting a couple of current photos.

 

[Halicarnassus]

LDC-26 ALBATROS — STAGE 1: THE ANALOG HEART & THE REBELLION

Fellow Music Lovers,

Today, I am not presenting just another piece of gear. This is the physical manifesto of a 60-year passion: LDC-26 ALBATROS.

Above, you can see the first images of our handcrafted "Analog Heart." This is not a mass-produced PCB from a giant factory; it is a labor of love, built with Point-to-Point mastery by Ahmet Usta. It is currently breathing for the first time in the workshop under testing, and the results are pure, unadulterated tube magic.

The Rebellion: Why Albatros?

For too long, we’ve been at the mercy of big corporations selling us overpriced, "closed-box" products. They charge thousands for mediocre engineering wrapped in fancy marketing. The Albatros is a rebellion against this status quo. We are proving that honest engineering and high-fidelity don't have to cost a fortune. I am building a bridge between the soul of 1950s tube technology and the precision of 2026 digital hardware.

The Blueprint (Roadmap)

This analog heart will soon be merged with our electronic module to become a complete hybrid instrument:

• The Great Decoupling: A dual-power architecture. Seamlessly switch between the mains and our internal Samsung 21700 DC block for 8 hours of total isolation from grid noise.
• Universal Input Hub: USB-C, Optical, and Coaxial digital inputs, paired with 2 Analog RCA inputs to handle all your sources.
• Professional Output Stage: Not just for headphones. Featuring 2 separate Analog RCA outputs including a dedicated Pre-Out, allowing you to command active monitors and external power amplifiers with tube warmth.
• Pure Control: Volume is managed by the legendary Khozmo 64-step attenuator, feeding 4.4mm, 6.35mm, and 3.5mm outputs.
• Universal Synergy: A Three-stage Gain Control (Low/Mid/High) to ensure perfect synergy with everything from sensitive IEMs to demanding full-size headphones.
• Wireless Freedom: High-end Bluetooth LDAC performance, stabilized by a Taoglas FXP73 external antenna system for uncompromising range and clarity.
• Visual Soul: A 30° tilted transparent panel with amber-lit Sifam VU meters. You won't just hear the music; you will see its heartbeat.

A Gift from Istanbul — Open Source Philosophy

Let me be clear: I am not here to sell you anything. Once finalized, all circuit diagrams, software, and the 1,000 Euro BOM (Bill of Materials) will be shared globally as Open Source. Why? Because I believe high-fidelity is a right, not a luxury reserved for the elite.

This is my gift to the community from the heart of Istanbul. Now, every talented and passionate audiophile will have the chance to own their own LDC-26 for 1,000 Euros—either by building it alone or as a team—without being ripped off by corporate giants and their multi-thousand dollar price tags for what essentially 4 different premium Hi-Fi devices can do in one.

My only goal is to share 60 years of knowledge without seeking a single cent in return.

HALICARNASSUS ( Mehmet Cengiz Yilmaz)

I FEEL GOOD!