Stage B: Transformers

Specifications and Ordering for Transformers and Chokes

1. Power Transformer (PTx):

   • Primary Voltage: Specify as 110-120V or 220-240V, depending on the region.

   • Secondary Voltage: Design based on amplifier requirements (e.g., 2x300V, 2x6.3V for heater etc).

   • Current Rating: Ensure sufficient current capacity for the amplifier’s needs. The inherent voltage regulation for the max current is less than 5%. 

   • Power Rating: Adequate power handling to match the amplifier’s output requirements with no power supply deterioration.

   • Regulation: Low voltage drop under load for stable operation.

   • Physical Size: Ensure it fits within the chassis design.

2. Choke:

   • Inductance: Specify according to design needs (e.g., 10H or as required).

   • Current Rating: Must handle the expected DC current without saturation. Must have gap.

   • Resistance: Low DC resistance to minimize power loss.

   • Physical Size: Should fit within the chassis and complement the overall design.

3. Output Transformers (OPT):

   • Primary Impedance: Match to the output tubes’ requirements (e.g., 4Ω, 8Ω, or as needed).

   • Secondary Impedance: Designed for optimal power transfer and frequency response.

   • Power Rating: Must handle the top rated valve's maximum output power. Single Ended means gap.

   • Bandwidth: Ensure full frequency response is covered.

   • Physical Size: Should align with chassis design and component layout.

Next Steps:

• Consult Manufacturer: Verify feasibility, performance, and cost considerations for each component.

• Place Order: Proceed with ordering the transformers and choke based on the final specifications and consultation feedback.

Stage C: Ordering components and chassis

All passive and active components have been ordered. Unfortunately, most Svetlana production was unavailable in the market, so preferred matched tube pairs from JJ were selected instead.

The initial mechanical designs and concepts have led to the decision to incorporate a wooden base for the amplifier. The layout will feature:

• Power Transformer (PTx) and Choke: Positioned on the right side of the wooden base.

• Output Transformers (OPT): Located on the left side.

• Aluminum Chassis: Placed in the center to house the electronics, including the tubes.

This design ensures a balanced and functional layout, integrating both aesthetic and practical elements.

Stage D: Waiting for components and Xformers

During the period while collecting all ordered parts, I designed and constructed a delay circuit using locally available materials. The circuit has been tested successfully to ensure it meets the design requirements.

Stage E: PCB CAD and test PCB Supplier.

While waiting for the transformers, I decided to design a PCB for the delay circuit and test the pilot production with PCB manufacturers. As an avid user of Linux OS, I chose KiCad for this task. KiCad's valve components, simple autorouter, and plugins for PCB manufacturers made the process straightforward and enjoyable. My first attempt at designing the PCB for the delay circuit was successful. The design phase was quick, the PCB ordering process was easy, and the trial PCBs arrived within a few days, all of which were of high quality.

Stage F: P2P assembly and test.

With all parts and the chassis now on hand, I began the placement and soldering of components and circuitry. The assembly and layout was in a P2P way. After verifying connectivity, the initial test was successful. Connecting a CD player and speakers to the amplifier produced sound of very high quality.

Stage G: Main PCB design/production, assembly.

Based on the successful proof of design and my experience with PCB design and production, I created the main PCB for the amplifier, which accommodates all circuitry except the magnetics and delay circuit. I placed the order with the same PCB manufacturer, specifying a thicker board and copper traces to ensure durability and performance.

At this stage, the amplifier was named Model A-SE. I also ordered new, more suitable components for the PCB, optimizing suppliers for the best quality. The assembly and layout were done in a point-to-point (P2P) manner. When everything arrived, assembling the PCB was straightforward, and the final result was both functional and visually appealing.

Stage H: Placing all electronics on base 

The final positions of the components on the wooden base were determined, and the placement and assembly began. The outcome exceeded expectations, with sound fidelity comparable to the point-to-point (P2P) assembly.

Basic testing was conducted, and measurements with 8Ω 3-way speakers showed that the power output was approximately 15W at 1000Hz, as anticipated. However, I have not yet been able to measure harmonic distortion due to limitations with my current oscilloscope. Specialized equipment will be needed for accurate distortion measurements.

Stage I: Cover Design

After much consideration, balancing functionality with aesthetics, the final choice for the top cover material is smoked transparent acrylic (plexiglass). This material not only delivers a modern, sleek appearance but also ensures durability and excellent insulation. The 5mm thickness provides structural stability, preventing any deformation over time.

To support efficient cooling, ventilation ducts and grills are strategically placed, ensuring airflow to the internal components. These vents also add character to the case, allowing the Lab Lampatos logo to stand out while showcasing the internal design for visual appeal.

The top cover will be easily removable, with secure fastening that maintains the overall robustness of the case.

After an extensive search for local plexiglass workshops, I found one equipped with Laser CNC technology and skilled technicians. They guided me on the technical details I needed to provide. As a Linux user, I designed the case in FreeCAD. Although the interface was initially challenging as a first-time user, I found it to be highly accurate and efficient once I became familiar with it.

As shown in the schematic and the accompanying photo, the final placement of the main components is carefully arranged for optimal performance and aesthetics. Viewing the amp from the front, the output transformers (OPTs) are positioned on the left, while the right side houses the power transformer, choke, and the delay circuit relay. Centrally located are the core electronic components, ensuring a balanced layout.

Construction began with the middle section of the cover, which accommodates these key electronic elements.

The PCB is now mounted onto the π-shaped middle plexiglass section, along with the VU meters. The back of this section houses the input and output connectors, while the front hosts the input selector, the power on/off switch, and the volume control, creating a clean and functional layout.

The PCB is now mounted onto the π-shaped middle plexiglass section, along with the VU meters. The back of this section houses the input and output connectors, while the front hosts the input selector, the power on/off switch, and the volume control, creating a clean and functional layout.

Beneath the PCB is an aluminum chassis, which houses the large power supply capacitors, the delay circuit PCB, and the VU meter PCB. This compact and well-organized arrangement has always been my preferred design, as it helps minimize noise and hum, contributing to a cleaner audio signal.

The precision of the design was evident once everything was assembled. The PCB fit perfectly into its designated space, and the valve bases and heated elements aligned flawlessly with the pre-cut holes and vents. The result was not only functional but also visually stunning.

The PCB is now mounted onto the π-shaped middle plexiglass section, along with the VU meters. The back of this section houses the input and output connectors, while the front hosts the input selector, the power on/off switch, and the volume control, creating a clean and functional layout.

Underneath the π-shaped section, lies an aluminum chassis used to house the delay circuit PCB, the VU-meter PCB and the power supply capacitors.

The side panels of our audio amplifier were meticulously designed using FreeCAD, ensuring both functionality and aesthetic appeal. These panels, shaped like open-ended boxes, provide crucial ventilation for the internal components. Vents are positioned at the back to manage airflow, while the front features a unique design where the brand's logo also functions as a vent.

After several iterations of testing, the logo vents were covered with colored panels to enhance the visual impact. After experimenting with various colors, a sleek green was chosen, offering a striking contrast that complements the overall design while maintaining optimal airflow.

The panels have been sent for pilot production at a specialized plexiglass workshop, using high-quality materials for durability and a professional finish.