why bass is tight and controlled on SS than chipamps like lm3886?

[jaycee]

I agree with the notion that a lot of the bad reputation of chipamps is the stupid "gainclone" philosophy. When treated like any other solid state power amp, ie with a good layout, proper decoupling close to the IC, a good heatsink, good stiff power supply and MOST importantly not trying to exceed the chips rating, they sound very good indeed especially given the simplicity.

I think trying to get the maximum 68W out of the LM3886 is half the trouble. Personally I wouldn't use it past 30W, i.e. 25v rails, giving plenty of margin.

I had the opportunity to compare my LM3386 amp against a relatively decent Arcam Alpha amplifier, and i couldn't really tell any difference. Both amps had 160VA transformers, and the Arcam had 1x6800uF per rail (35v) versus my chipamp's 2x4700uF per rail (25v).

I do suspect that chipamps might be a bit suspect with complex loads, but for driving my Wharfedales and Eltax Liberty 5's, they sound great

[MJL21193]

Well said jaycee,
But it falls on deaf ears. The OP has his mind made up, he just asked to hear his view parroted by a few others.

[PMA]

My small contribution:

[megajocke]

"I think trying to get the maximum 68W out of the LM3886 is half the trouble. Personally I wouldn't use it past 30W, i.e. 25v rails, giving plenty of margin."

Yeah, that's probably a very good idea - SOA is a bit challenged and contrary to discrete BJT:s with huge chips these have pretty short thermal time constants. (A typical big BJT like 2SC5200 can take for 10ms double the peak power a LM3886 output transistor can for *0.1ms*)

[AndrewT]

Hi,
I think that the 3886 is suitable for big power into high impedance loads of around 8ohm. eg. 60W into 8r0 using quiescent rails of +-37V sagging to +-34V on full power. This is despite the fact that these chipamps were never intended for this purpose when initially released for consumer electronics.

I have stated repeatedly that if designing for lower impedance loads then the power should be scaled down. I have suggested 30W to 40W maximum for 4ohm loading.

[Bonsai]

I agree.

If you have realistic aspirations for a gainclone, the performance can be VERY good.

[SpeakerScott]

Originally posted by megajocke
"I think trying to get the maximum 68W out of the LM3886 is half the trouble. Personally I wouldn't use it past 30W, i.e. 25v rails, giving plenty of margin."

Yeah, that's probably a very good idea - SOA is a bit challenged and contrary to discrete BJT:s with huge chips these have pretty short thermal time constants. (A typical big BJT like 2SC5200 can take for 10ms double the peak power a LM3886 output transistor can for *0.1ms*)

I've made very similar plots to yours with BJTs, MOSFETS and several different chip-amps...and I can't agree more. The 3886 doesn't have the "guts" of a discrete amp. National's data sheet is partially responsible, claiming power ratings under conditions that are likely only to happen during development when you can absolutely control the load and rail voltage. To their credit, they do tell you all about the chip, and study the document long enough you'll figure out what it can and cannot do.

I've built them before...for what I wanted them to do (quick, cheap, easy to construct amps) they were great.

When I want more power and better sound quality, I go discrete.

Scott