An open source layout for LM3886?

[NealJ]

Originally Posted by viki_v2

Has anyone built this amp.

I built it for a friend 18 months ago, I think it is excellent.

I have the Gerber files available on my hobby website (with links to this page) and they have been accessed over 1000 times, so I would say there are probably a fair few completed amps out there. Very few people come to this page asking for help which could suggest they haven't had any real problems with it.

It's relatively cheap to build, why not just send the files off and give it a go?

[454Casull]

What is the largest AWG stranded copper wires that can reasonably fit in the PCB terminal through-holes?

[00940]

AWG18 should fit without problem, AWG16 will be too tight. The drill hole is a 1.3mm one.

[454Casull]

Originally Posted by 00940

AWG18 should fit without problem, AWG16 will be too tight. The drill hole is a 1.3mm one.

Thanks for confirming the drill size. My digital calipers aren't good enough (and probably aren't the right tool) to check them since I get a reading of 1.2x mm.

I was considering whether to solder wires directly to the board or use a terminal block. At the end of the day I suppose anything other than soldering (at least for my application) would just be a waste of time and money, as 18 AWG is more than enough for how much power I need out of these.

[silasmellor]

Originally Posted by viki_v2

Has anyone built this amp.

I built one for my summer house, sounds great recommended

[Dibya]

Anyone can please list me values of components for PSU and DC protect?

[00940]

for the DC protect: An open source layout for LM3886?

for the PSU: ok, a bom was here: An open source layout for LM3886? but it's not fully correct. Caps and resistors should be fine but the final version uses the bridges mentioned in post 63. The heatsink should rather be the Ohmite RA-T2X-38E

[lost eden]

Originally Posted by viki_v2

Has anyone built this amp.

I just realised I only posted my build to the main gallery thread & never actually contributed back to this thread. I finally finished it back in May this year, after starting in 2018.

It is a 3 channel build for a 2.1 setup, with two of the boards bridged via a Vigortronix VTX-101-007 audio transformer. There is a lot of empty space in the enclosure because I originally intended to house an active crossover & its power supply in the same enclosure, but in the end I stuck with my separate dbx crossover. I know my hand wound coils are bad, but I have to leave myself something to improve on next time.

I also built a 3U rack from some cheap plywood.

I am very happy with the results. I used my last gainclone for 8+ years & I now intend to use this one for 8+ more.

[eisp4nzer]

Originally Posted by 00940

Well, there are two issues here. One is how things are joined and the impact of common tracks' impedance. No objection on that, the feedback cap has to go to the input gndplane. The other thing, less clear, is about loop area and radiations pickup. Groundplanes are relevant to both issues as provide a low impedance connection but also allow to reduce some loops.

So, here's an attempt to satisfy all the compromises. Yeah, I wish... As before, the zip is for the eagle files.

The feedback cap now returns to the input gnd. The feedback resistor going to gnd is over the split between the signal and the power gndplanes. If you consider the loop mentioned in the post above, it's quite tight.

The two gndplanes are joined near the output connectors by a resistor. It can be jumpered in case of a mono amp.

Better now ?

First of all, many thanks... I've been looking for a project like this for so long...
I'm planning on printing the PCB's and make (another) an amp for myself
So... I have some questions:
Are these gerber the final version? Anything I should be worried about? Do you have a BOM's list? (found them, thanks)I don't want to mess it up
And thank you so much for all that work, it looks amazing by the way

[eisp4nzer]

Originally Posted by Mark Whitney

That is exactly how this chipamp mania started.
Attachment 677920

WTF is that?