What is the difference between a "Model Q" and a "Son of Q?"

First of all, the most obvious difference is price.  Son of Q models generally cost approximately 1/2 of its parent version, the Model Q.

The next obvious question is why?  To understand this, first one should look inside a Model Q and check out the quality of the components and the extensive workmanship involved in its manufacture.  Every jumper wire is made of 99.97% pure oxygen-free copper wire (if it's good enough to wire an F15 cockpit, it's good enough for the Model Q) that is hand cut, sleeved and terminated with 20,000psi pure copper ring terminals, then neatly heat shrinked to reduce the possibility of any electrical mishaps.  The Son of Q uses high temperature stranded copper jumper wires made of more common commercial grade pure copper but every jumper is terminated identically to the Model Q jumpers. 

The transformers are also different but both are MASSIVE!  One significant difference between the two is they type of steel used in the transformer core material.  The Model Q uses the industry's finest quality Silicon grain oreinted Steel, more than twice as much of it as is required for the power rating of the transformer.  Furthermore, the transformer is designed to run cool in the chassis so the danger of heating up a rack or a cabinet is remote if even possible at all.  The Son of Q transformer uses a typical nickel steel alloy that costs much less to produce.  Though the alloy may not have as high of a magnetic flux capacity of the finer silicon grain oriented steel, but again as the case with the Model Q, the Son of Q has an overabundance of mass in it's core.  (approx 1.7 times what would be needed for the power requirement of the transformer.)  Both transformers are bifilar wound and are extremely accurate, however there is an extra step taken in the Model Q version that further reduces output assymetry and adds to the cost.  Model Q transformers cost approximately 3x as much to fabricate as the Son of Q version does, however both are extremely accurate and can handle current trasients better than any other transformer designed for the purpose. 

Because of the difference in weight, the Model Q has a thicker guage steel chassis to support its massive transformer.  Aside from an LED voltmeter on the Model Q, its spec grade outlets, its near-perfect symmetry and the quality of the materials and components used in its manufacture, the Son of Q is very similar because it's design closely follows the Model Q specifications.  The Son of Q provides extremely good current response, high power factor, a cleaner more well defined bottom end, finer detail and a quiet noise-free background that runs circles around competitive products, but the Model Q does it better.