First Lm3886

[PJPro]

Originally posted by Stuey
......You'll get access to the ESP secure site once you've ordered. The page for Project 39 has VERY comprehensive info, including a very clear drawing of how to wire it up to the switch and IEC socket.

Looking forward to getting access to those pages.....

[AndrewT]

Originally posted by PJPro

OK. So the large cap on its own isn't going to provide a RF filtering solution.


So I'd need a ferrite bead in series with the large cap? What does LS mean? Sorry for not knowing this.


Thanks. Hopefully, with advice from yourself and others, it'll be safe and sound good too.

Hi PJ,
this posting from Infinia was a reponse in answer to my post where Infinia became convinced I had made some kind of error in my advice.
It was specifically written to make my writing appear foolish.
Do not try to extract from the wording used any useful practices for your own use.
It was directed to me and should be read in that context.

[AndrewT]

PJ,
things are getting very complicated.
Your build is becoming a labour of love.
It will take you a long time, it is costing you a lot of money partly because your Bill of Materials (BOM) is being added to ad infinitum.

I suggest you stop and rethink your build strategy.
1.) build a simple prototype fixed to a piece of chipboard.
2.) fit the absolute minimum to get a chip amp working. No nice to have add ons.
3.) power up this single channel with everything exposed, but keep the pets/children locked up/out.
4.) listen to it powering one channel for an extended series of listening sessions including background music as well as specific Audio events.
5.) decide if a £4 chipamp deserves the £hundreds spent on all the paraphernalia you are accumulating.

Maybe your targets will change after you have built your first prototype, or maybe you will spends dozens of hours casing up your project.
I'd suggest you make this final decision after you have heard the chipamp playing in the typical usage you intend to use it.

[PJPro]

Yes. It had occurred to me that I might be turd polishing.

The saving grace is my ultimate plans to upgrade the chipamp and power supply for discrete units (as you recommended earlier). So, all the bits can be reused. I will not skimp on safety and most of the additions relate to this crucial aspect of the build.

But yes. Thanks. Your advice is duly noted.

[PJPro]

Oh. And I'm learning a lot about the true complexities of comprehensive build. Doubtless, this will be invaluable when I consider future, more exacting projects.

[PJPro]

Did I mention that I'd also bought the P33 speaker protection project from ESP as well?

But no more. That's it. Until it's built and working.

[anatech]

Hi PJPro,
Thank you, you have done a fair amount of work getting those links together. You also have your answer already from other members on that inductor.

The advice that AndrewT is giving you is excellent. I have often advised people to do the same thing. Get it running before trying changes that are supposed to make it sound better. I would view the protection relay as a required part, no surprise to those who read my posts.

Once you have things running along, you can try some suggestions and part changes. I would leave all parts in that are in the app note. They were designed in for a reason and far be it for anyone but an expert to second guess the people who designed the chip.

As far as " It had occurred to me that I might be turd polishing", you never know. ICs and general circuitry have come a great long way since I was starting out. The cheaper stuff in my time sounded truly horrid. The "cheap" chip amp projects sound so much better these days that I feel your amp will have worth. So, if you don't care for it as a main system, it will be a killer computer speaker amp. My home is filled with amplifier experiments that sound good, but not great. My friends and kids have benefited from my experiments as well. What can be improved to you may sound like magic to someone else. You can only judge from what you have heard so far.

The building of a project has far more value than the item it may become. To put it another, over used way, "the trip is worth more than the destination". I have many things I built in the 70s that still work. My kids are amazed when they figure out I was their age when I did these things. I was just surprised to see them.

-Chris

[PJPro]

Thanks anatech.

As I said, I feel that I have identified all the bits I need and am in the process of ordering them. It's all good fun, even if it's working out a lot more expensive than I originally estimated. Still, if a jobs worth doing......

My only real concern is that the more components I add, the harder it will be to trace and identify a fault, should it occur. I guess the best method to counter this is to be extra thorough when putting it all together.

Oh. The boards and mosfets from AMB Labs arrived this morning. Excellent quality and a worthy addition to the project.

[AndrewT]

Originally posted by PJPro
My only real concern is that the more components I add, the harder it will be to trace and identify a fault, should it occur. I guess the best method to counter this is to be extra thorough when putting it all together.

even more reason to build it up as a single channel prototype on an insulating flat panel.
Start with the transformer. Add a rectifier. Add some smoothing Add the SIMPLE amplifier. Add the input filtering. Add the mains filtering. Add the DC detect. Add the output relay. Add the .... etc.

Once you have one channel working, then start all over again on the second channel and prove it.

Now work out how to package that 3foot long assembly inside your box.
Only then do you spend the time to get the final look that you want.

[Greg Erskine]

hi PJPro,

I'm not sure if it has been mentioned but always measure Vdc offset whenever you do a change to your amp. It should be below 100mV most of the time with chipamps. After that, connect a cheap test speaker and have a listen (and smell).

BTW: It is possible to polish a turd, I saw it on Myth Busters.

regards