The 2026 board is built around a common-base transistor stage, chosen because it provides one of the most stable amplifier configurations. Its job is to supply a steady current for a pair of LDRs, each drawing up to about 7 mA. At lower currents, the circuit always references the load to maintain consistent behaviour.

 

Although the NSL32SR3 LDR is specified with a 2.5 V forward voltage, real measurements show that it actually becomes active at about 1.50–1.58 V, and its resistance can vary widely—from around 60 Ω up to over 25 MΩ.

 

To correctly match this behaviour, the board applies the load in four stages, each one bringing the operating point closer to the LDRs’ true forward-voltage requirements.

1. First stage:
   Resistive loading is applied to both the shunt and series LDR pairs. This stage reflects the important fact that LDRs are current-driven devices, not voltage-driven.

2. Second stage:
   A half-wave rectifier is used. The anode receives the Focus and Start currents, and the cathode outputs a rectified version of this current.

3. Third stage:
   A passive (non-active) transistor pair provides further shaping and isolation of the load.

4. Fourth stage:
   This stage allows both the first rectifier and the wiper load to act as an “anode” for the incoming AC signal before the main rectification occurs.

Between each rectifier stage, a 100 µF capacitor is placed between anodes. This unusual arrangement does not boost voltage in the way rectification normally does—it actually smooths differences and slightly reduces voltage, helping the earlier stages behave predictably.

 

The board also includes optocouplers, which allow each input signal to be detected optically. Even though they act as switches, they also supply a small amount of additional current to the circuit. Mid-stage regulators and further rectifiers control inrush current to both the series and shunt LDRs.

 

The Focus control sends current to the cathode of the shunt LDR pair. This increases their resistance, which helps preserve the correct source impedance and prevents unwanted loading of the audio source.

Overall, this design improves on typical passive attenuators by using LDR pairs in a way that avoids the usual weaknesses. Instead of burdening the source, the circuit reveals more of the source component’s true capability—something often hidden by conventional attenuation methods.

 

Another observation is that the behavior of resistance itself seems to “stretch” or extend, almost as if each ohm does more work than expected—if such a thing is possible.

 

We don’t usually think of resistance as having extra properties beyond simply opposing current. We tend to assume that resistance is a fixed, final value with no hidden refinements. Normally, resistance is measured as a load to ground. But in this design, the ground reference is allowed to exist before the resistance itself fully forms, meaning the potential for resistance appears only after the grounding condition is established.

 

Surprisingly, even the definition of an ohm wasn’t fully stabilized until the 2019 revision of the SI system, which finally tied electrical units directly to physical constants. This highlights how subtle the nature of “one ohm” can actually be.