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Topics - joecool85

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Amplifier Discussion / Best Battery Powered Amp Contest!
« on: January 12, 2010, 06:28:22 PM »
Hi Guys, time to ring in the new year with a new contest!

Post your battery powered amps.  Please include pictures, description of circuit or schematic, and (if possible) sound clips.

Since battery powered amps tend to be a stepping stone into AC powered amps, I'll be giving out kits for AC powered amps for the winners.

First Place:  Stereo LM1875 Kit from, Mono LM3886 board (with integrated PSU) and 25 chip points.

Two Runners Up:  Mono LM3886 board (with integrated PSU) and 10 chip points.

Thanks go to Brian at for making this contest possible, all boards and kits are from his store.

The contest only goes until January 31st!
Free shipping for the prizes!

Amplifier Discussion / Need help wiring transformer
« on: August 29, 2009, 06:31:11 PM »
I'm working on a test board for an lm3886 from brian and I can't get the psu wired up right.

I have a 18-0-18 VCT tranny, the board has two holes labeled AC1 and two holes labeled AC2.  It also has a hole labeled GND.  I have 3 wires coming off my tranny, two hots and one neutral.  I split the neutral so that it went to one of the AC1 holes and one of the AC2 holes and then sent one hot wire to each of the other AC1 and AC2 holes - I didn't hook anything to GND.  All I get is a blown 1amp fuse.  So I replace the fuse with a 2amp, because thats what you normally use with an LM3886 anyway, and the tranny gets hot, the diodes get hot and the tranny hums.  And its not rectifying to DC either.

What am I doing wrong here?  Do I need to jumper some other wires and send the neutral to GND on the board?

Amplifier Discussion / Is my sub's transformer wired in reverse?
« on: August 27, 2009, 07:31:06 AM »
Hi guys.  I was going to use the transformer out of an unused (but working) home entertainment sub for a LM3886 project.  The caps on the board are 35v, and the transformer is huge, so thats a good sign.  Anyway, the mains power is connected to the transformer on FOUR wires.  Black from the wall goes to black and red on the transformer and white on the wall goes to white and brown on the transformer.  Then on the other side of the transformer there are three wires, two red and a black.  What's with the 4 wires on the primary side?  Or is this thing maybe hooked up backwards?

Amplifier Discussion / Contest
« on: August 19, 2009, 06:51:46 PM »
Post your pics of your chip amp builds (anything from kits to self made amps and boards are fine).  The winner of the "best chip amp" will get a free t-shirt shipped to their door AND 25 Chip Points!  Thanks go to Brian at for donating this shirt and helping out as always.

Pictures may be submitted until 9pm EST on Saturday September 5, 2009.  The decision will be made by the following Monday and the shirt will ship as soon as the winner PMs me their mailing address.

Let the contest - BEGIN!

**If anyone has issues posting pictures, please PM me or post a question in The Newcomer's Forum**

Tubes and Hybrids / Other tubes
« on: March 13, 2008, 08:47:57 PM »
So I'm thinking my next tube amp will be in the 2-5 watt range and I don't want to deal with more than 100-120v or so.  The 50C5 is a tempting choice putting out 2.3w @ 120v.  Any other tubes that meet this criteria?

Tubes and Hybrids / How to wire tubes
« on: March 06, 2008, 04:31:35 PM »
How do I know what pins go to what wire?  I'm working from this schematic:

It says about how to wire the heaters, but that's it.

Tubes and Hybrids / 12v 12U7/12AL8 amp, have a few Q's
« on: August 11, 2007, 12:30:04 PM »
I'd like to build this tube amp using a 12U7 and a 12AL8 tube.

More info here:

Now, I've never built a tube amp before and I've always wanted to.  This little fella seems pretty cool but I have some questions.  What do I use for a PSU?  Could I basically just use a 12v regulated source and a 5000uF cap for filtering?

Where does the volume pot go on this thing?  Could I have a gain control on this?

I've priced out parts and I can get everything minus an enclosure and a speaker for around $50.  I'm going to do a lot more reading on tube stuff before setting out to build it, as I always research heavily before getting into a new project.

Also, what about biasing the tubes?  Hows that work?

Yes, I am a tube newb.

Amplifier Discussion / Dual mono = dual transformer?
« on: January 13, 2007, 11:31:23 AM »
I know normally when you do a dual mono you would do two transformers, one for each PSU board...but I have a 330VA transformer running my mono LM3886 and want to add another channel.  I have the stuff for a dual mono, or I could just build the amp board and use the existing PSU board.  Would it better to use the existing PSU board to run both LM3886 amp channels, or build another PSU board and split the power from the transformer to both boards?  This is going to be for a bass rig btw.

Amplifier Discussion / Possibly silly questions, splitting signal
« on: January 06, 2007, 06:27:30 PM »
Alright, my brother is getting my LM3886 setup and adding another LM3886 to make it a dual mono, he wants both channels driven by one input.  Couldn't we just tie the two inputs together?  From what I gather, we can, since they are all on the same ground and whatnot.

The Newcomer's Forum / Rules for Newcomers Forum
« on: October 23, 2006, 10:05:42 AM »
1.  All questions are important, none are stupid
2.  No flaming allowed (this applies to the rest of the forum anyway)

That's basically it.  Other than the obvious; read and post often  :tu:

Amplifier Discussion / LM1875 chipamps, any feedback?
« on: October 17, 2006, 03:29:40 PM »
How do you guys like your LM1875 kits?  We spread out quite a few kits, it would be nice to know how well they are working.

Preamps and Effects / TL071 preamp = super easy
« on: July 07, 2006, 07:18:00 PM »
Paul has been so kind as to do an easy layout for it too:

This would be PERFECT for any chipamp guitar amp.

Preamps and Effects / Sparkle boost preamp
« on: July 02, 2006, 09:08:23 AM »
I've been doing some searching and apparently the sparke boost has so much boost that it is actually too much sometimes, this sounds perfect for a preamp to me!  Anyone want to try it out?

Alright, I have  kits that will be complete in a couple weeks.  The pricing is $14, this includes the boards, chips, resistors and caps for a stereo LM1875 along with First Class shipping.  If you want priority shipping it will be $17.  The reason they are more expensive is because Brian didn't have everything so I had to order a good amount of parts from digikey which upped the price a bunch.

If you are interested, post here because its first come first serve.

Paypal payment to

If paypal is a problem for you, PM me to work something out with check or money order.

Here are some PDFs that will help you out:

The manual is unfinished, but it has everything you will need to know.

Amplifier Discussion / Good news
« on: June 21, 2006, 05:47:26 PM »
The LM1875 kits should be ready in a couple weeks.  I know I already said that a while ago, but I've been really busy.  I am placing the order with digikey right now for the parts I need.

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