509X sounds nothing like the 590AXII which is what the OP is asking about.
If you look here they are basically the same amp, using different rail voltage that's all, which gives different wattage's and biasing.
The 509 has a cover over the transformer also.
https://lh3.googleusercontent.com/proxy/gP0nqKbQWosy-DiN2-qMpDFVdUMyKiXRMD5mJkDFOdkGjdxLo8KNm4WJbxEU...
https://cdn.shopify.com/s/files/1/1040/6126/products/luxman-l-590axii-integrated-amplifier-luxman-2_...
Cheers George

