LM3886 power supply

[HRDSTL]

I used the source from the post #1,and slightly modified...
1. The diodes will be used BY880-400-DIO (400V / 8A)
2. The value of c8 and c11 reduced to 22nf
3. Capacitor values around diodes reduced to 47n

 

[pbilous]

I frequently deploy a C+RC snubber across each transformer secondary, where Cx=Cacross is implemented as an MOV (metal oxide varistor) instead of a capacitor. The MOV (a) is about the same cost; (b) can be Quasimodo-optimized for critical damping just like a capacitor, and (c) adds an extra layer of surge protection, for free. To see one example, search the Forums for threads with "VRDN" in the title.

Will something like this work? - https://www.mouser.com/ProductDetail/Bourns/MOV-07D470K?qs=lgttKnAd%2B2DrMJUU5I413w==

I am assuming I would use two of them - one for each transformer secondary coil - those are 25V AC each.

 

[pbilous]

Another revision of the PCB - more affordable to build. Size is 100mm by 75mm.

 

[nigelwright7557]

The single bridge is good, less components to go wrong and less space.
I would put the decoupling caps at the amp chip power pins.
A tip for chip amps is keep feedback loop as short as possible as 1mm = 1nH of inductance.

 

[pbilous]

Just finished building my LM3886 amp and used only 10,000uF per channel for the power supply filtering. Guess what, the voltage without load is 62V, but with the load, the voltage dips to 58V! It looks like adding more of the capacitance is essential.

 

[pbilous]

Redesigned psu board to be able to accept four big capacitors now.

 

[pbilous]

Cleaned up schematics little bit. Also added MOV across the 50V output from the transformer.

 

[HRDSTL]

Could you do an add with the CRC and fuse holders? It wouldn't go amiss...

 

[pbilous]

Could you do an add with the CRC and fuse holders? It wouldn't go amiss...

CRC? Like a filter?

 

[pbilous]

Added resistor in front of the filtering 10,000uF capacitor. Gerbers are attached.

 

[pbilous]

Could you do an add with the CRC and fuse holders? It wouldn't go amiss...

Here is the thread where I simulated multiple scenarios in the LTspice. I don't think that CRC filtering is the best way to go for the power supply - https://www.diyaudio.com/community/...us-crc-filter-simulation.386838/#post-7037446

Law of diminishing returns. No resistor and four 10,000uF caps gets you variation of 1V. Add two 0.22R resistors (CRC filter) and the variation is in the range of 0.65V. Adding four 0.22R resistors (RCRC) reduces variation to 0.55V. Not worth it in my opinion.

 

[pbilous]

Here is for anyone who would like to use CRC arrangement - gerber files attached.

 

[pbilous]

Photo dump of assembled psu board:

 

[pbilous]

FIXED MAJOR MISTAKE IN THE LAYOUT!!!

Pinout of the LM337 in TO-220 package is not the same as with LM317!

Pin 1 is ADJ for both LM317 and LM337

Pin 2 is IN for LM337
Pin 3 is OUT for LM337

Pin 2 is OUT for LM317
Pin 3 is IN for LM317

Attached are the schematics and gerbers with the correct layout.

 

[lisoformio]

Hi gooduser, where I can find the easyEDA design files? Open source?

 

[pbilous]

Revisiting this thread as I am creating new design layout in KiCAD now. Schematics attached reflects all of the components that might be placed but could be omitted. Main filter caps are 6800uF and are 25mm in diameter. Makes for a nice compact PSU board.

 

[NanoFarad]

which is enough for a stereo set up.