It's always interesting to have a look under the 'hood....
First the Levinson...
And then the Proceed...
In the case of the Levinson instead of having the toroidal transformers mounted sideways (as was done in the Proceed HPA) they instead mounted the transformers in a more conventional upright manner. When they did this they also eliminated the shielding that the Proceed used to cover the transformers and they also shortened the length of the internal heat sinks to accommodate the less efficient use of space. According to my friend who worked there, this made those amps much easier (read less expensive to build) but not necessarily an improvement over the HPA…..