The 10KPP82 push-pull audio output transformer for ECL82/PCL82/6BM8 tubes is designed for tube-audio enthusiasts who want to achieve a warm, detailed sound. The transformer is intended for use in class-A push-pull configuration and can deliver 6 watts RMS output power.

Features:

• Primary impedance: 10 k? anode-to-anode
• Secondary impedances: 4/6/8 ohms
• Primary inductance: 92 H at 2 V, 100 Hz
• Leakage inductance: 47 mH at 1 kHz
• Primary DC resistance: 520 + 520 ohms
• GO-oriented grain core laminations
• 6 W RMS power capability
• Designed for ECL82/PCL82/6BM8 tubes
• Flexible secondary impedances

Winding the prototype transformer is a crucial step in creating a high-quality product. These photos show me at work, with precision and attention to detail, to ensure a result that meets my standards.

To ensure the quality of the push-pull audio output transformer for ECL82/PCL82/6BM8 tubes, I carried out a series of bench tests with real PCL82 tubes. These tests included frequency response measurements. In the photo you can see the push-pull audio output transformer for ECL82/PCL82/6BM8 tubes connected to a pair of PCL82 tubes on a test bench. This setup is representative of a typical tube amplifier for loudspeakers.

Frequency response graph

The zero-feedback frequency response of the push-pull audio output transformer for ECL82/PCL82/6BM8 tubes is 10 Hz to 45 kHz at –1 dB. This graph might appear unusual but has an explanation. The transformer was tested with pentodes connected as pentodes. The internal pentode of the PCL82 has an internal resistance of 16 k?. As explained in another article, with pentodes it is physically impossible to create transformers that are perfect at low frequencies. The primary inductance is never sufficient and, if you try to increase it beyond certain levels or use exotic cores, you encounter other issues such as saturation phenomena.

Nevertheless, achieving –1 dB at 10 Hz, even if the graph seems to fall slightly from 1 kHz downward, is an excellent result. It should be noted that, with 16 k?, the pentode section of the ECL/PCL82 is not as critical as an EL84 (38 k?).

It is therefore clear that this transformer must be used in a feedback-applied circuit. This is the proper way to operate any circuit using pentodes as output tubes. Without negative feedback, in fact, the damping factor settles at about 0.6, which is too low.

For those who may not yet appreciate it, at zero feedback this is a remarkable result. When used in a circuit with even minimal negative feedback, this transformer can deliver a full, uncompromised audio range.

Let’s also look at the square-wave response (1 kHz)

Typical connection diagram

The diagram shows how the push-pull audio output transformer for ECL82/PCL82/6BM8 tubes can be connected to a pair of output pentodes. This schematic is only indicative and can be adapted to specific project requirements, for example with fixed-bias operation.

Dimensions (mm)
L	85
H	100
S	104
F	68
F2	58

Dimension diagram

Conclusion:

The push-pull audio output transformer for ECL82/PCL82/6BM8 tubes is a high-quality product that provides warm, detailed sound. It is an excellent choice for tube-audio enthusiasts who want to get the best performance from their system.