DPP's / STK's and "BPC"
Aldo,
As far as I know, Sanyo was definitely one of the leaders in building and utilizing 'STK" technology, and I'm sure it gets lots of cursing and blame for contributing to the end of the vintage era. Darlington power packs are NOT the same as a completely integrated "hybrid" IC amp, and really are just the output section (complementary power transistors) integrated into a large and electrically isolated package - the amps that use them I still consider to be "discrete" designs, and have input, VAS and driver stages identical to designs that employ true all discrete output parts. The Darlington power pack defintely eased manufacturing costs since they dont require electrical isolation, they can simply be bolted "naked" right to the flat surface of a heatsink, the heatsink also required less machining (dont have to drill complex hole patterns) than the TO-3 metal cans that they replaced. IMHO, this allowed a little more compactness in the 50WPC or so class, but I agree with gonzo 100 percent, if designs that employed DPP's did not skimp on power supply capacity, they made for some great performing and sounding amps, even up into the 75 to 90 WPC class. The largest DPP's may have even reached up beyond 100WPC (Fisher RS-20xx ??)
The "hybrid audio amp IC" took integration all the way, and stuffed all of the components into the IC, except for any high value capacitors that were physically impossible to build in an IC. Even this has its advantages, and also made for some great units before the "black plastic plague" came into full force by about 1983. Thermally, there can be some argument for the advantage of all the amps components being the same temperature, but again, it was cheapening of the power supply and reducing it's capacity that really was the downward spiral of the "BPC" syndrome.
The era of the Darlington Power Pack, as opposed to the fully integrated STK amp, did not really have a long run and were popular only for a few years at the end of what most of us recognize as "Vintage". After that, DPP's may have still been utilized, but not to the same degree, and the really high power stuff, even branded Sanyo, Fisher etc. - still used multiple discrete output devices to achieve 120 WPC and more, for example my Sanyo JCX-2900K.
On a whole, I would not judge a unit on the use of DPP's or even Hybrid chip amps based on that alone, surprisingly, one of the most coveted "monster" receivers of all time, the KR-9600 utilized Sanken produced Hybrid amp IC's, but look at it's power supply - there is where the rubber meets the road, and it is massive and dual-mono, and although there has been some cursing of this unit based on replacing those hard to get modules, most continue to perform today, and can compete with any design, pure discrete, or not.
My worthless and prolly inaccurate $.02
