LM4780 which setup should i use?

[filholder]

I have a set of Kef Concerto one, resonably decent floor standers. They have a quoted impedance of 8 ohms and a sewnsitivity of about 90dB.

http://www.kef.com/history/1990_2/concerto1.asp

I can drive then very happily using a LM3886 or even a single AMP3.
However i have recently come across some huge 22000uf 63v caps and couple of huge transfomer and a few LM4780. I was think about trying to build LM4780 power amp just for fun to see how it compares to my other homebrew amps. My question is what setup would work best for my set up, or at least what should work bets since i guess it is very hard to say defintively.

I have 4 lm4780 so i could do a pretty wide set of setups, bi amping each speaker and each of those could be a bridged or pararelled 3886 inside the 4780s. Obviously more wattage is not really and issue however i guess some more grunt might help in controllign the speakers

Any idea which might work best?

Any suggestions greatfully recieved,

Phil

 

[Tweeker]

No point in paralleling 3886s @ 8 ohms.

 

[filholder]

So your saying that I cannot use a Lm4780 for my speakers unless say I use each on the amp in the package for say the bass and treble units.

So one Lm4780 per speaker and each of lm3886 in the packaes will be used for a different drive units.

That make sense?

Are the massive 22000uf caps i found any use in a setup such as this? Obviously i guess they will need a snubber or else i will get negative effects.

 

[Tweeker]

Im saying there is no point in paralleling 3386s @ 8 ohms.

Bridging (and possibly bridging and paralleling) and/or biamping is another matter. DRV 134 is a popular choice for phase splitting duties.

Theres some very nifty, though more technical bridged chipamp (GCSS) designs in the Passlabs forum.

 

[pinkmouse]

I would go for a bridged LM4780 for the bottom, with your big caps, and a LM3886 with 1000uF for the tops. Snubbers are up to you but I never found them particularly efficacious.

As you say you have plenty of 4780s, then I would second Tweeker's suggestion to look at some of the Pass Labs circuits. The PSU will be the same for those and for the more conventional bridge circuits, so extra cost will be minimal if you don't like them.

 

[jackinnj]

the bridged version has a slightly lower THD -- in any event these things do like to be well heatsinked -- and the bypass capacitors (100nF in parallel with 10uF) immediately adjacent to the power pins will help you avoid problems with the thermal protection., motorboating etc.

 

[filholder]

The GCSupSy thread seems pretty interesting, i am going to go through that first since i appears to be a real gold mine of idea on what to do when you have some chip amps in hand. Having paid for my samples of the LM3875 and LM4780 i want to find something interesting and worthwhiel to do to then. A nelson Pass design might seem like a decent idea.

Cheers guys, i really didnt know he had done any designs using chipamps.

Phil