Lm4780/lm3886 vs Transistor Amp


2011-02-24 5:04 pm
an ic amp can be a transistor amp, as the ic contains the transistors, they are all just semiconductors.
think about an ic like a circuitboard with every part allready inside and assembled.
i know it a verry crude description, and may not be accurate technically, but the logic is proper.
when you make a discrete amplifier from components, the matching of the components can be a challange that you never face with an ic.

i suggest the lm4780 as an amp chip out of this list.
if your goal is some really heavy deep bass , then the first step is actualy a good driver, and a proper cabinet for the task, the amplifier is the last part to figure out.
it can happen with ease that you don't need more of an amp than the trusty sta540.
it depends on the environment where you want to use it, and the subwoofer you want to drive, and the result you want to acheve (-3dbl point, peak spl, ...)
The "thumping bass" is not really about the amplifier type. It's about the speaker system and its capability to waft ever larger amounts of air around! Use the biggest speaker driver (or two) you can get away with. Remember the size of the box these driver(s) will need will need to be accounted for, too. If using a IC amp, use 4 ohms (or 4 ohms combined if more than one driver)as you'll get more current (= more power) but check the IC ratings at 4 ohms.
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the amp must be able to drive the given speaker, if the amp can not drie a 4 ohm speaker, then it should not be conencted to one.
Yes, one must DESIGN the amplifier to suit a range of loads.
Advice to attach a lower impedance load is very bad advice !
If using a IC amp, use 4 ohms
is about the worst advice I have seen for a 4780/3886 chipamp.
A ClassD amp will normally surpass an LM3886 on bass quality. If you don't need too many watts, try a TDA8932. Best bass I've ever had from a chipamp.
It would be safe to say: The TDA8932 Datasheet Schematic has better quality bass than either the LM3886 Datasheet Schematic or the TDA7293 Datasheet Schematic.

Actually, all three of the parts that I mentioned can be set for the same fantastic bass; so, a limitation of bass quality, does not exist inside the chips.
The limitation is documentation (the older linear chips have generic schemas in their datasheets, with placeholder values instead of application optimized performance).

For 40 watts of rather fantastic quality bass, to an 8 ohm woofer, all three chips mentioned in this post do have a point of awkwardness:
Thermal management, probably involving a kapton sheet and heatsink as big as the board, some paste and bolts. It can reach 40W usable music power if lightly loaded.
T-Net Inverting, using the component values for LM3875 T-Net Inverting from Decibel Dungeon. This plan is not for tweeters. Under-volt to achieve 40W to 8R with good efficiency.
I have two nice schematics for it; however, there is still the inconvenience of trimming the gain factor differently for any power voltage difference. Under-volt to achieve 40W to 8R with good efficiency.

So, doing the same job with all three chips, is not difficult.
TDA8932's power circuit will cost at least 20% less; however, the many other costs of a completed amplifier, will swamp that one difference.
Also noteworthy is that by adding ~$2 for an additional chip, TDA7293's capacity goes up to 90W to 4R.


2012-12-11 10:10 pm
It is easy to design transistors amplifier with better specification than LM3886 :cool:

If you want build sub woofer amplifier, I suggest to choose transistors amplifier that use symmetrical VAS. Example: Soopky amplifier, Symetri amplifier that design by Ostripper. You can find it somewhere in this forum.
?????? No results from search. Do you have a link?