HPW seemed to be unafraid of the mathematics involved in the noise calculations. JLH eventually ran out of arguments in favour of his shunt feedback RIAA circuit.
Even back in the valve era, where shunt feedback around a pentode was not uncommon for the equalized input stage, it was known that the cartridge loading resistor could place a limit as to how far the noise floor could go. For example, in respect of its 22 control unit, Quad said, in respect of noise,
“-80 dB or the where applicable, the equivalent noise of the pick-up load impedance at the input.”
In the valve era, using series feedback to avoid the input load resistor noise issue was more difficult, as a double triode with DC heating (at least on the input stage) would have been required. But in the solid-state era, series feedback was easily done with a two or three-transistor stage. That being so, why consider a shunt feedback equalized input stage? In the end, JLH could not provide a cogent argument for so doing.
HPW’s design also created another, but shorter debate about his use of bootstrapping in his tone control module. See WW 1972 May p.225 and WW 1972 September p.423.
HPW was just preceded by Quilter, who published his bootstrapped tone control circuit in WW 1971 April, pp.199,200. This was intended to improve upon the Bailey 1966 circuit, which Quilter had commented upon in WW 1970 April p.172.
Quilter was generally credited with this improvement – which became part of the “Bailey-Burrows-Quilter” control unit circuit, although it does appear to have had prior use, for example in the Quad 33:
JLH had used a jfet to obtain high enough open loop gain in his 1969 modular design:
Cheers,