MyRefC build guide

Thanks regiregi for the .rar file. It is very helpful. I am using version 1.4.

As a newbie to this stuff, I am trying to really organize to build 4 kits in a batch style and have sorted out all components into test tubes in racks. I am having a little difficulty identifying some components. Some of my questions might help revise the BOM to reflect exactly what is in the kits.

D2, D3, and D4 appear to the the same 1N4001 diode.

There are two 3K3 resistors where one appears to be a 1/4 watt and the other a 1/2 watt resistor to go in R12, R37 slots. Which slot, R12 or R37, gets the bigger resistor? I know I should be able to read the schematic and figure it out. I am working on understanding the amp but is is a little tougher design than some to grasp the concept.

Has C34 been dropped from the build? I can't identify any capacitor as a 10 pF in any of my 4 kits.

Can 1/4 watt resistors be mounted in contact with the PCB?

I know to raise the higher wattage resistors 8mm for cooling.

If i am using a 60/40 solder with flux core, is additional flux overkill?

I am sure I'll have more questions but let the soldering commence.


rick, D2, D3 and D4 are 1N4001.

For the two 3K3 resistors from different wattage, Uriah should answer. One is the input resistor in series with signal and the other one is in series with a 1nF cap between the input and the inverted input from the LM3886. I don't think neither of them will need to be 1/2W at all. But in the BOM, R12 is 1/2 and R37 is 1/4, so put it that way.

I don't know how the C34 kemet cap is, but a picture should help. Should be one of the smallest one. But it is for sure on the BOM.

The 1/4W resistors can be mounted directoly on the PCB.

You will not need flux at all if your solder and your iron and decent enough. Just give it a fast and hot solder process.

Here is a bill of materials and schematic for the parts supplied in the kit for one channel. There are other bills in the threads, but this is what I actually received.

As Dario noted, parts used in the relay circuit can be generic industrial components as audio specialty parts are of no advantage. The relay circuit has a few problems and I will be modifying the circuit in my build. The attached file shows what I am changing and why.


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Here are some questions and answers I put together before I decided whether to run the group buy or not. A huge amount of information.
My "audiophile" LM3886 approach
Original introduction and subsequent design thread.
Can I ask the orginal designer some questions? No. He is a good guy but he no longer participates on this forum.
My "audiophile" LM3886 approach
Thats for gerbers, boms, etc.
My "audiophile" LM3886 approach
Single sided for etching.
The Dim-bulb Radio Tester
Lets just say that when firing it up for the first time, if you dont use this or a Variac, then dont blame anyone else if something goes 'poof.'
My "audiophile" LM3886 approach
24V secondaries are best but 22V would be fine..
My "audiophile" LM3886 approach
A discussion about grounding as it can be a bit confusing with this amp.
understanding star grounding
Grounding - Read this please
My "audiophile" LM3886 approach
What pot to use?
My "audiophile" LM3886 approach
Many caps on the board are .22uf but spec'd for .1 in Mauro's schematic. Why the change?
The new "My Ref" Rev C thread
Dont try to improve it with the normal "tweaks". This amp is tweaked already. Leave the opamp alone. Just stop. Resist.
The new "My Ref" Rev C thread
Fuse and switch installed correctly.
The new "My Ref" Rev C thread
what it looks like assembled.
The new "My Ref" Rev C thread
Can I use different diodes instead of the recommended rectification?
The new "My Ref" Rev C thread
Should I put fuses on the secondaries?
The new "My Ref" Rev C thread
DC offset at output of amp. Whats okay? How do I measure it?
The new "My Ref" Rev C thread
I want the technically perfect heatsink. If you just want a guess then us a 2.5"x2.5"2" cpu heatsink.
The new "My Ref" Rev C thread
Is it worth the build?
The new "My Ref" Rev C thread
I want to swap my own caps. How should I do that so I dont end up over soldering the board and lifting a trace?
The new "My Ref" Rev C thread
I have noise after putting in large input caps or just some hiss anyway, here is one explanation.
The new "My Ref" Rev C thread
Should I do MonoBlocks? Well, I dont know but there is a discussion here.
The new "My Ref" Rev C thread
I like cap swapping. Anything else I might like ?

Picasa Web Albums - Peter - RevC Measurem...
Some REVC measurements from Peter

From Mauro's webpage:
Passing band (typical-3db): 2Hz-70Khz
* The maximum power (8ohm): 40Wrms
* The maximum power (4ohm): 56Wrms
* Damping factor (8ohm): >200
* Relationship S/N (600ohm): >96 dB not weighed
* Typical THD (20Hz-20Khz, 1-40W 8ohm <0,05%

The new "My Ref" Rev C thread
Cap recommendations by Dario

I have a pic of the top of the board.. pdf below
Also an eagle schematic

Attached Files
File Type: pdf prod_revc.pdf (83.9 KB, 86 views)
File Type: pdf revcschem9-1-2006.pdf