This one's on clearance at PartsExpress...
http://www.partsexpress.com/pe/pshowdetl.cfm?&DID=7&Partnumber=129-075&ctab=14#Tabs
Will it work?
Looks like it has a pair of secondaries 16-0-16 rated at 0.5A on each side... I can't tell how much current the LM3886 'wants' from the data sheet... I see plots with supply voltage vs current - these currents are all in the 60mA range... then I see the 7A min in the table at the beginning...

Thanks in advance!!
Mike

Yes, it is a BrianGT mono kit.

So is this circuit designed for a line level input (as opposed to an instrument/guitar level input)?  I read several posts over at diystompboxes.com from folks (including Joecool85) who built this chipamp for guitar use... it's interesting to hear tha we're all using it 'wrong'. 

Won't running the guitar into an effect essentially provide the power amp a signal with the appropriate impedance?  Most of my DIY stompboxes have a 1M pulldown resistor on the input (to avoid loading the signal).  Is this sufficient?  If not, could you point me to a good, clean/transparent DIY preamp (post a link?)?  The main goal of using a chipamp as a guitar power amp (in my case, anyway) is to amplify my guitar and effect pedals without coloration.  I could see using a clean MOSFET booster, like an ROG Omega, for the clean 'channel' and one of my SansAmp GT2's for the distorted sounds... or am I missing the point?

Thanks for the feedback... so much to learn!
Mike

Hi guys.
Just wanted to send out a special thanks for all your help in getting my LM3886 chipamp going.  I spent this morning assembling/wiring it.  Worked great the first time I turned it on!!  I wired the level pot backwards (no biggie) but everything else was just fine.  Very neutral clean tone - really shows the speaker/cab/guitar 'sound'.  I was a little surprised that there wasn't more output volume available - but I didn't mess with the I/O resistors... just added the level pot (not like there's not enough volume...).  I'm sure it would be louder running into 4-ohms instead of my 8-ohm Swamp Thang...
I put together a little webpage documenting my components for future newbie builder reference.  Have a look.

http://www.freewebs.com/mydementia/LM3886/myLM3886amp.htm

Thanks again!!
Mike

Thanks guys - I DID put in the resistors across the big caps... now I know why - Thanks!!
teemuk - looks like a good read... more than I should do at work.
I'm going to crawl back into my hole and read tonight... I'll be back...
Mike

Hi Guys.
I've been highly distracted with all the new stompboxes over on Aron's forum, but am finally getting back to this project.  I soldered up my chipamp.com boards last night - what a joy!  I bought the mono kit from Brian a couple months ago... very professional looking. 

So...
1) I bought this transformer from PartsExpress following this forum (and Brian at chipamp.com) recommendations:
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=122-615
I'm still not satisfied with my enclosure - but really want to put this beast together.  I want to build it up on a wood block just to get it all working... so my question here is about grounding... Am I creating my 'star' grounding from the 'ground' pole of my AC Jack? 

2) The 10000uF caps on the power board scare me... Do I need to treat them as high-voltage power caps (using a 5W, 10ohm resistor to the positive lead with the other end clipped to ground) - or are they more innocent than I think?  I just don't want to get dead...   Other 'drainage' techniques appreciated...

Thanks for looking.
Mike

How about an old P4 CPU Heatsink?  Looks like 1.25" tall, 2.75x3.25" with 23 fins...
I'm running a single LM3886 (PS and Amp boards/kits from Brian at chipamp.com) with 22-0-22V from the transformer into an 8-ohm load oughtta give about 35W... maybe this will work?

This reminds me of a heat transfer problem from college...

Which dissipates more heat, a heatsink exposed to a volume of ambient air constantly increasing in temperature (Conduction path: Chip-->Heatsink-->Air-->Aluminum Enclosure), or a highly conductive heatsink (copper chunk) thermally coupled to the aluminum enclosure (thus conducting to the larger aluminum enclosure to an ~infinite volume of constantly 'cool' air (Conduction path: Chip-->Copper chunk-->Aluminum Enclosure)

Here's a snapshot of the 'gainclone' that caused me to raise this question:

Yeah, Steve, I saw those sinks on your site...
I also dug around chipamp.com in the 'completed builds' section and saw one guy using a 3x4x0.5" hunk of copper - that sounds better to me than trying to accommodate a big finned heatsink (something in the 4x6x8" range). 
I'm still looking...
mike

Hey guys.
I just got my transformer from partsexpress and my boards from Brian at chipamp.com (prettiest boards I've ever seen!!).  All I'm lacking is some sort of chassis and a heat sink (the 'huge' box I wanted to use isn't quite 'huge' enough...).  I started really looking at the schematics and the transformer label and want to make sure I have it...  Does this look right?


Any recommendations on a place to find a cheap chassis and/or heatsink?

Thanks for looking...
Mike

I must have mistaken the little giz-widgets behind the cap in the front of the picture for regulators... maybe I'll just build the GGG bipolar power supply...

Right - so I'm thinking I'll try the toroidal (http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=122-615).

If I would buy a power board from Brian over at chipamp.com like this one:


could I run a second lead from the +DC voltage (not sure what Brian's kit produces - no regulators are identified...but I assume it's around 20VDC to run the 3886) to a daughter board with a +9V regulator to give myself a 9V power source for external effects/preamp (and for potentially driving a fan)?
Mike

Right on - but what about the transformer?  Do I need to buy a $50 toroidal, or can I get away with the 'el cheapo' one from Partsexpress?
Mike

Hi guys.
I'm tired of hauling my tube amp to my buddy's house for practice so I'm going to finish my other speaker cab and build an LM3886 amp (got the chip with my last Futurlec order...) to leave there (that way, I can bring my pedal-du-juor or my SansampGT2 for a preamp). 
I started digging around for a transformer and wonder if this one will work:
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=129-035

Also, regarding heat sinks... how big does it REALLY need to be?  The two in JoeCool's pictures (sticky thread in this forum) are HUGE!!!

Thanks for looking.
Mike