Hi all 
I've been perusing what info I could gather in here, on designing and building an LM3886 amp. Specially this thread: Newbie LM3886 Circuit
I've also been going thru this guide: A Complete Guide to Design and Build a Hi-Fi LM3886 Amplifier - Circuit Basics
and Tom's pages Taming the LM3886 Chip Amplifier
I exchanged messages with Tom a couple of years ago, but I didn't have money to spare at that time. I'm a musician and music teacher, so of course now my financial situation is.....less.....
But at least I can learn, so I'm trying to wrap my head around all aspects of the circuit (yeah, the info on Tom's pages still seem to slip out again).
Anyway, I have a question about Tom's circuit, if it's not inapropriate! If I see it corretly, the zobel network is connectet CR, not RC (cap connected to pin3). Any reason for this (hope it's ok to ask - Tom?). If not, I'll delete this thread.
Cheers
I've been perusing what info I could gather in here, on designing and building an LM3886 amp. Specially this thread: Newbie LM3886 Circuit
I've also been going thru this guide: A Complete Guide to Design and Build a Hi-Fi LM3886 Amplifier - Circuit Basics
and Tom's pages Taming the LM3886 Chip Amplifier
I exchanged messages with Tom a couple of years ago, but I didn't have money to spare at that time. I'm a musician and music teacher, so of course now my financial situation is.....less.....
But at least I can learn, so I'm trying to wrap my head around all aspects of the circuit (yeah, the info on Tom's pages still seem to slip out again).
Anyway, I have a question about Tom's circuit, if it's not inapropriate! If I see it corretly, the zobel network is connectet CR, not RC (cap connected to pin3). Any reason for this (hope it's ok to ask - Tom?). If not, I'll delete this thread.
Cheers
A+B = B+A
The impedance of the Zobel network is the sum of the impedance of the resistor and the impedance of the capacitor:
Ztotal = R+1/(j*2*pi*f*C) = 1/(j*2*pi*f*C)+R
Thus, the order of the components doesn't matter. Or as my undergraduate honours advisor once put it, "the electrons don't know which end of the wire they're in".
On the PCB layout, I can sometimes squeeze the small capacitor into places where the larger power resistor couldn't go. This may dictate the order of the parts. In the layout process I try to minimize the parasitic inductance of the Zobel network, i.e. minimize trace lengths.
Hope this helps.
Tom
The impedance of the Zobel network is the sum of the impedance of the resistor and the impedance of the capacitor:
Ztotal = R+1/(j*2*pi*f*C) = 1/(j*2*pi*f*C)+R
Thus, the order of the components doesn't matter. Or as my undergraduate honours advisor once put it, "the electrons don't know which end of the wire they're in".
On the PCB layout, I can sometimes squeeze the small capacitor into places where the larger power resistor couldn't go. This may dictate the order of the parts. In the layout process I try to minimize the parasitic inductance of the Zobel network, i.e. minimize trace lengths.
Hope this helps.
Tom
Thanks for posting all those links. Looks like I have a lot of reading to do. I became interested in the LM3886 myself when I found one driving the tweeter in the JBL LSR28P. I followed the schematic from the data sheet and made a working amp PCB pretty easily. There are models out there for the LM3886 in the Tina spice simulator that allow you to check your customized circuit. There are guys in China selling kits on ebay at ridiculously low prices, $10. I have bought a few of those and they worked great.
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