LM3886 optimisation and power supply review

[esl 63]

You can use a 1000uF cap instead with lower esl and esr... much better!

 

[tsiros]

shouldn't there be a fuse on the mains wiring?

 

[AndrewT]

There is, it is labeled "F"

 

[tsiros]

Ah, indeed. I see it now, It's the huge white box between transformer and switch. I initially thought that was a fuse for Vcc level.

 

[cvpho1]

You can use a 1000uF cap instead with lower esl and esr... much better!

I already had the caps and the main reason using two 4700uF was space limitation (but also two capacitors in parallel will reduce ESR due to internal resistors in parallel).

 

[cvpho1]

See Rod Elliott's article on Ground Loop Breakers. Earthing (Grounding) Your Hi-Fi - Tricks and Techniques

National does advise 100nF ceramic and 10uF electrolytic as close to the power pins of the LM3886 as possible.

The two caps you are mentioning to are already near the LM3886, please see the first posted diagram, not the PSU.

 

[AndrewT]

two caps or four caps?
Each Cs is an electrolytic and a ceramic.
A Cs attached to +ve and -ve supply pins = four caps.

 

[cvpho1]

two caps or four caps?
Each Cs is an electrolytic and a ceramic.
A Cs attached to +ve and -ve supply pins = four caps.

More clearly...

The diagram of the amplifier in post #1 is for one channel and has two Cs (one for V+ and one for V-). Each Cs has a 0.1uF, 10uF and 1000uF near each LM3886.

In the second diagram in post #1 and post #38 (thanks for protection improvement), the PSU I'm using most of the time for testing has two 4700uF in parallel with a 1uF for V+ and the same for V-.

 

[cvpho1]

I’ve modified the case, the same internal circuit, now with a much bigger heatsink. We’ll wait for the summer to see the difference (hot room around 30 C).
Regards

43°C at the heatsink, or at the exposed tab, or for Tc.
Ts=43°C is hot, by my reckoning, because that gives Tc~50°C

If ambient rises, then Tc approaching 60°C becomes possible.
That would be way over the Tc=25°C that National use to show the 3886 performance.

 

[cvpho1]

Now, in a 20 C room, after listening a couple of hours classical music at normal level, the DC offset was 2mV on left channel and 3mV on the right.

I’ve modified the case, the same internal circuit, now with a much bigger heatsink. We’ll wait for the summer to see the difference (hot room around 30 C).
Regards

 

[AndrewT]

Now, in a 20 C room, after listening a couple of hours classical music at normal level, the DC offset was 2mV on left channel and 3mV on the right.

that's a good result.