Who has built the Circuit Basics LM3886?

[DaveFred]

I am wondering if anyone on here has built the Circuit Basics LM3886 amplifier exactly as shown on the web site?

What did you think of it?

A Complete Guide to Design and Build a Hi-Fi LM3886 Amplifier - Circuit Basics

Thank you,

David.

[TasKitas]

Hello David,

I have built it following the guide, although this is my first amp.

The guide is very good, it helped me to understand what does specific combinations of components do and how important are the values.

I've used components something in the middle of price/quality that I could get locally. For me, quality sounds good, although can't compare if it's better or worse than another amp

Furthermore, until I’ll get better speakers, I can't hear the full potential.

Mindaugas

[rmlazzari]

I haven't assembled the recalculated circuit yet but I used this guide to recalculate the components in order to get something close to 20W @ 4ohm at the output. Surprisingly, no component in the signal path seems to have been affected, that is, the only changes, if I did not make a mistake in the calculations, ended up being in the power supply. The great attraction of this LM3886 chip is the very low distortion, since for 20w there are only many other options on the market. But, as I said, none with such small distortions.

I also found the use of zener on pin 8 (mute) quite ingenious, dispensing with the use of another circuit just to take care of the soft-start.

As for the formulas for filters and gain, they are very close to those I found on another site of a profound student of this chip, Neurochrome and its Taming teh LM3886. In fact, the Neurochrome class, in addition to offering the PCB ready in a stunning finish, carries out a very, very in-depth study of this chip, it is worth taking a look.

[wgh52]

Thanks for link to this very instructive and seemingly exhaustive design info on the LM3886!

I am missing one thing, though, and would like to understand why this consideration may not be relevant for LM3886 designs:

How are speakers protected against potential too high Output DC voltage? E.g. caused by LM3886 failure shorting the chip's Output to V+ or V-. Is this output DC protection inherent to the Chip? Or why is my concern a non-issue?

Thanks and Regards,
Winfried

[tomchr]

Originally Posted by rmlazzari

I also found the use of zener on pin 8 (mute) quite ingenious, dispensing with the use of another circuit just to take care of the soft-start.

Yeah. Pretty good idea. Though if you size Rmute for ~1 mA at the nominal supply voltage, you don't need the zener.

Originally Posted by rmlazzari

As for the formulas for filters and gain, they are very close to those I found on another site of a profound student of this chip, Neurochrome and its Taming teh LM3886. In fact, the Neurochrome class, in addition to offering the PCB ready in a stunning finish, carries out a very, very in-depth study of this chip, it is worth taking a look.

Thank you. I appreciate your compliments. Here's a link to the Taming the LM3886 series: Taming the LM3886 Chip Amplifier – Neurochrome

Tom

[tomchr]

Originally Posted by wgh52

How are speakers protected against potential too high Output DC voltage? E.g. caused by LM3886 failure shorting the chip's Output to V+ or V-. Is this output DC protection inherent to the Chip? Or why is my concern a non-issue?

The LM3886 itself does not provide protection against excessive DC on the output. That said, you can design an LM3886 amp for pretty low offset (~2 mV is the nominal offset), so excessive DC is only an issue if the amp fail catastrophically. This is pretty darn unlikely, but if you do wish to add speaker protection to your amp a circuit such as the Guardian-86 will be helpful.

Tom

[wgh52]

Hi Tom,

thanks for your hint! One reason for my question is the fact that the drivers of my (vintage) 4-Way active Speaker are not not available as spare parts anymore A DC-protection circuitry in addition to the already existing power-on-delay and AC-lost muting circuitry seemed a meaningful investment to me (if not inherent to the Chipamp ).

As I'm designing an own SSR solution, a DC sensing bit with LED indicator will be added to the SSR circuitry which is also controlled by pwr-on-delay and AC-lost detection.

Regards,
Winfried