Been reading the updates in the newest edition of Power Amplifier Design Handbook. It is with some interest he discusses many of the wonder patent ideas (my words) I have been reading about from the 80's. I had been wondering why if these ideas solved so many problems, why are they not SOP today? Was it that the shift to portability and video-centric caused it to not relevant in the market? Answer seems to be they did not work as well as hoped.
My first quick pass through seems to read that his continued research into the matter has not changed his basic conclusions on topology.
My first quick pass through seems to read that his continued research into the matter has not changed his basic conclusions on topology.
I always wonder why Peter Walkers Current Dumper has not proliferated, now the patent is expired. Todays undersized internal heatsinks in so many amplifiers seem to make it attractive for anything more powerful than a chip amp.
Hi,
Feedforward (Quads schema is one form of it) is alive
and well in many commercial amplifiers. Though details
are generally hard to come by, and very often are
obfuscated by marketing buzzwords and speak.
rgds, sreten.
Feedforward (Quads schema is one form of it) is alive
and well in many commercial amplifiers. Though details
are generally hard to come by, and very often are
obfuscated by marketing buzzwords and speak.
rgds, sreten.
Sad state of affairs, just a few months out and some of the "new" transistors he suggests are already OBE.
I was glad to see a lot more details explained with SPICE, but he is assuming more than general knowledge on it's use. A lot more details on why you may or may not want to do some things in the IPS and VAS. Some "why" for transistor selection.
You can get rip-off copied fake Quad boards from China off e-bay. His position is still that it is not necessary. Basically endorsing TMC on the standard architecture is good enough.
I was glad to see a lot more details explained with SPICE, but he is assuming more than general knowledge on it's use. A lot more details on why you may or may not want to do some things in the IPS and VAS. Some "why" for transistor selection.
You can get rip-off copied fake Quad boards from China off e-bay. His position is still that it is not necessary. Basically endorsing TMC on the standard architecture is good enough.
I have been surprised that the driver in a Quad 405 I had for a while a home became very hot.
If you mean the buffer on the opamp, that is in class A and gets hot by design. My point is that the Quad design does not depend on sensor transistor thermal tracking or the use of exotic power devices with built in diode sensors to avoid run away
Apparently the people at THX have "re-patented" the idea recently. It was
authored by Laurie Fincham.
😎
It remains the most original circuit of all the solid-state era.
As far as I remember, it is Tr7 which becomes very hot, it is in class A and provides all the current to linearize the output stage where BDY77s Tr9 and Tr10 work in class C..
It has about 50mA through it so 1W. For some reason the 306,606 etc changed to a discrete voltage amplifier and TR1 to a LM334 2mA current source. My simulations show an issue there as the LM334 mis-behaves at >2V/us slew rate. This is easily exceeded when the dumper devices activate
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