Performance of Chip Amps

[Phil Olson]

I was thinking of doing a chip amp design based on the LME49810 and was wondering how it would compare to my Bryston 4B-ST's. Specifically, are these chip amps true audiophile quality, regarding noise, distortion, etc. The spec sheet shows rather low THD, comparable to the Brystons so I was just curious.

My application will be a tri amped active crossover speaker HT system so that rules out buying a bunch of Brystons!

On the other hand building up a couple dozen chip amp boards and designing them into the speaker bases would be sweet.

I was thinking one FET pair for the tweeter, two pairs for the mid and three for the woofer. All would be nominal 4 ohm.

Opinions?

[sangram]

Chipamps offer simple construction for above average sound. They are kind of reliant on the structure of the load - or maybe it's just my horrible building and wiring techniques. What works for one pair of speakers doesn't work for the others.

Whether they can compete with a Bryston or not I can't tell, but they easily beat out amps costing 10 times of themselves, such as the entry levels NADs and Cambridge Audios.

However I'm not sure they can go head-to-head with really good discretes. I do know that construction and overall implementation play a huge role in final performance of the chipamp. Just because it's in a chip doesn't mean you can slap on a few components and call it a day - the same effort is required to make it sound good.

Live example: My hard-wired LM3886 (P2P) sounds much better than a LM4780 BPA I built from Peter Daniel's kit on my regular mid-fi speakers (>89dB, 8 ohm, gentle loads). The same BPA amp absolutely trounces the LM3886 on a pair of Dynaudio passives, rated 86dB and 4 ohm.

For your case a chipamp would eliminate complexity and reduce cost. The Orions are similar, and use 60 watt/channel discrete amplifiers (but built into one case) for a similar task.

[Nuuk]

For most of us, going active and needing say six channels of amplification, rules out costly amplifiers anyway. This is where chip amps really come into their own. As Sangram says, SL finds them good enough for his Orion speakers. Another example is this design that also used chip amps to keep the whole project affordable.

And don't forget, with active speakers, the amp doesn't have to cope with a passive crossover between it and the driver, making it an easier load that chip amps prefer!

[SpittinLLama]

The LME49810 is not a typical chipamp which the popular LM3886 is an example of. the LME49810 is the front end potion of an amplifier and you add the output stage, as you have noted. It can sound very good when done right, better than the full chipamps like the LM3886.

For your design that is a lot of power unless you are running low rails. Depending on the output devices used, you can easily get 100W from a pair of FETs for the tweeter. 100W into a tweeter should be very overkill. Anyway, the rest sounds like a lot of power too but for the bass driver it might be a good amount. Having more power doesn't hurt unless your speakers cannot handle it and you burn them up. Search on LME49810 kits and try one out first to see what you think. Then you can go buy or design/build the other 5 amps.

-SL

[Phil Olson]

Thanks guys. The speakers I am building are WMTMW so there will be two mids and two woofers, hence the extra transistors.

I am currently doing a design that I will try to post later for feedback.

Thanks again!