User Manual Q&AAnswer
Feb 15, 2025 - 12:53 AM
The pmillett Sangaku DIY R2 PCB has a known error that causes a DC offset to appear on the unbalanced outputs and preamp outputs. This issue does not affect balanced headphones as the offsets cancel out. The mistake in the PCB design is that the signal was taken from the wrong side of the 100 ohm resistor on the JFET buffers between the nutube plates and the opamp output stages.
To fix the DC offset issue, there are two possible rework methods:
1. Swap the leads on the JFETs Q6 and Q7:
- Carefully swap the two leads of the JFETs, ensuring that the leads do not short circuit.
- You may use insulation, such as the stripped insulation from a piece of hookup wire, to cover one or two leads to prevent shorting.
2. Cut traces on the back side of the PCB and add a wire:
- Cut the traces on the back side of the PCB as shown in the manual.
- Add a wire to reroute the signal to the correct location, as indicated in the manual.
Please refer to the manual for detailed instructions and illustrations on how to perform these rework methods.
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