| theChris |
just interesting stuff. i've made a small PCB file for a lm4780 using the high input impedance IGC circuit i've been looking at for a while. it's amazing what car all fit on the PCB.
it's a circuit with 3 feedback resistors in a network, 1 input resistor and input cap. a zobel resistor and cap, the cap across the + and - inputs, 3 PSU caps sized for a 1000uF, 10uF, and 0.1uF cap. 27pin case. 2 bias resistors.
everything but the mute resistor and cap... the mute fuction can still work.
size is 2.2" x 1.2" about 60mm x 30mm. no space is wasted...
in anycase it's just interesting to see how small a PCB can get. i mean the IC is made for 120 watts -- 45 watts per square inch!
i'm thinking about modding them into AC-coupled difference amps for use as IGC, NIGC, or difference amps. then the IC could be used as a parallel IC (using 0.1ohm copper resistors...) or bridged using 1 IGC and 1 NIGC, or stereo amps.
no mounting holes though.
as additional info, i'm working on 2 other GC based projects -- an active filter that is modular, and a mod to the GC to make subwoofer amps more efficient. |
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| JCoffey |
| I'd definately like to see what you've come up with. I have 4 4780's and I'd love to take two and bridge each one to build a pair of 120 watt Monos, in a NIGC layout. Since I have no idea what I'm doing laying out PCB's, something like this would be perfect. |
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| theChris |
| ok, i'll try to mod the miniboard out for a NIGC instead of my I3GC idea. i plan to get them made on monday. the guys in charge of the macheine are having a bit of trouble with the software aspect. |
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| JCoffey |
| How difficult do you think it will be to bridge? And how much are the boards going to cost? |
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| theChris |
i'm not really sure if i'm going to sell them yet or not. shipping costs of course, but i'm not sure i can print them on-demand...
i was originally planning on selling them for less then $5 each, or maby $5. as i see it if i sell too high, i feel bad and get potentially fewer customers. but too low and i get too many orders or people wanting to make orders, and if i can't print them on demand, well, i just end up disappointing too many people and feeling bad anyways.
also, it will depend on shipping costs. if shipping is $5 and the boards are $1, then everyone buys 5-10 boards even if they don't need to, this way they pay less per board and feel good about themselves. if shipping is only $1, and the boards are $5, then people buy about how many are needed with possibly one extra. most likely no more then twice what is needed.
but like i said, i'll try to get the difference amp PCB and a guide made up. since i don't plan on using it, favoring the trial of my I3GC, and given your plan on using it for a bridge app, i'll probably just charge you shipping if the boards work. then you can tell me if the boards worked fine, which i would assume they would, and from there i can decide if i should sell them online or not.
like i said, if i make a difference amp version, then bridgeing would be easy enough, as the difference amp can be converted into NIGC or IGC, or 2 difference amps would work as well. |
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| JCoffey |
| Sounds like a plan then. and with the amount of people that are wanting to try the 4780's, these pcbs would be perfect.... |
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