13), or is it more complex than that? I see that Keith connects various points in the pcb to different ends of R2 in different revisions of the mods (see the evolution schematics from the link in the first post). Shopuld the direct 0V connection be reserved as far as possible for the dumper circuit, connecting all the previous points to the raised signal ground which is taken from the RCA input connectors (Tibi/Tvicol seems to d this in his Quaser rev.
This raises the general question of the ideal schema for internal grounding in amplifiers. R14 is still replaced by R13 in the implementation, which does still go to signal ground. This is in line with the illustrated implementation. I was looking at an early revision of DCD Mod4 and see that Keith in a later revision changed R101 to go to DUMPER ground. Is the schematic an improvement on the implementations, or vice-versa?ĭoes in tot matter which way round as long as there's one connecting to each of the grounds?ĭo the values of R101 and R13/14 depend on which ground is being used? What are the consequences of each way of doing this? The schematic shows R14 between the collector of TR1a and DUMPER ground, whereas the implementations connect TR1a collector to SIGNAL ground through R13Ĭonversely, the schematic shows R101 between SIGNAL ground and Q45(TR11) collector, whereas the implemetations have R101 connecting to DUMPER ground. What do you think about their function?Ģ. The schematic shows R104/R105 feeding the bases of TR9 and TR10, but these are missing on the illustrated implementations.
QUAD 405-2 Amplifier Modification and Informationġ. I'm prepping the boards now and and have them pretty much sorted, but see a couple of inconsistencies between Keith's schematic (P.12)Īnd the illustrated implementations on his website. They are well made clones of M12368 pcb-s and can be relatively easily modified. "Class A dynamic biasing 80W amplifier PCB Quad 405"īoards from Jim's Audio on Ebay Class A dynamic biasing 80W amplifier PCB Quad 405 2pcs | eBay I'm building an implementation of Keith Snook's DCD-Mod4 on
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