Great review! I enjoy these reviews of some audio-gear classics. 
Bybee "Labs" "Music Rail"; ModWright tubes ; Cardas RCAs; "The Pulse Gen ZX" internal power supply enhancement, with voodoo crystals. Upgrades?
The original power supply was probably drowned by the massive flow of snake-oil that poured from this "ModWright" unit.
This snake-oil was purchased to the level where ModWright was able to start an actual tube audio company. They market a full line of pricey tube products. Their 'discontinued modifcations' list shows they did 'upgrades' for 3 OPPO models, and about 10 other audio products.
One of their first tube 'upgrades' was the SlimDevices/Logitech Transporter, a streamer/DAC/digital preamp, in 2008. The ModWright Transporter was a $2000 upgrade for your Transporter (which was already a $2K device), or for $3600 they'd sell you a model direct. The power supply was also 'upgraded,' to include an audiophile-approved mass of copper. 6 Moons did a nice overview of the mods, actually worth a look. For $2K, they did fill the box....
I recently retired a 'stock' Transporter, in continual use since 2007. I did replace the power supply -- the small, yellow board -- for ~$10. Retired the unit for a WiiM Ultra, of course.
This shows 'before' and a small 'after':
Here's a larger 'after':
Bybee "Labs" "Music Rail"; ModWright tubes ; Cardas RCAs; "The Pulse Gen ZX" internal power supply enhancement, with voodoo crystals. Upgrades?
The original power supply was probably drowned by the massive flow of snake-oil that poured from this "ModWright" unit.

This snake-oil was purchased to the level where ModWright was able to start an actual tube audio company. They market a full line of pricey tube products. Their 'discontinued modifcations' list shows they did 'upgrades' for 3 OPPO models, and about 10 other audio products.
One of their first tube 'upgrades' was the SlimDevices/Logitech Transporter, a streamer/DAC/digital preamp, in 2008. The ModWright Transporter was a $2000 upgrade for your Transporter (which was already a $2K device), or for $3600 they'd sell you a model direct. The power supply was also 'upgraded,' to include an audiophile-approved mass of copper. 6 Moons did a nice overview of the mods, actually worth a look. For $2K, they did fill the box....
I recently retired a 'stock' Transporter, in continual use since 2007. I did replace the power supply -- the small, yellow board -- for ~$10. Retired the unit for a WiiM Ultra, of course.
This shows 'before' and a small 'after':
Here's a larger 'after':
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