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Topics - joecool85

Preamps and Effects / Sweet tube preamp on ebay
April 19, 2006, 07:52:43 PM

I don't have the money for it, but it'd be perfect for a chip amp application!
I've been thinking about trying to find a preamp, but if you buy them new they seem pretty pricey.  Anyone have any luck with using a preamp to a power amp?  IE - Dean Markley (or any other brand) preamp to PA or something?
Brian is setting me up with a couple lm1875 kits and maybe a lm4780 kit.  They should be in by the beginning of next week.  Who is interested?

I don't know exactly what I'll be getting, so I can't garantee anything till it comes in the mail, but its kinda first come first serve.  I'll just have you pay shipping.  Oh, and Brian wants whoever gets the kits to build them and take a bunch of photos.
I saw one on ebay a while ago for $20, and I love my K-20X, anyone know anything about the PAs they put out?  This one was a spectra 400a or something.
Nelson posted this over at diystompboxes and said I could post it here.  The layout is unverified, but oh so cool.
Nelson posted this over at diystompboxes and said I could post it here.  The layout is unverified, but oh so cool.
Preamps and Effects / Chipamp preamp
April 07, 2006, 10:50:13 AM
Chipamps are designed so that they don't need a preamp, however, that is for when you are running a lineout from a computer, CD player etc.  This means that you need to get guitar signal up to that strength by way of a preamp.

So, here is what we need in a preamp:

- Gets us up to linelevel
- basic EQ (probably 3 band)
- protection, ex-someone pluging in AC power to the input
- input buffer of around 1m
Amplifier Discussion / Heatsinks for your poweramp
April 05, 2006, 07:37:26 PM
First - Have a good power supply circuit and a big enough/proper voltage transformer
Second - Big heatsink, there is no such thing as too large of a heatsink

Proper heatsink size for two LM1875 chips, or one LM3886:

Overkill(which isn't a bad thing though):
Schematics and Layouts / LM1875 Power amp schematic
April 05, 2006, 07:09:19 PM
Now hosted on ssg server.

The lm1875 makes a really killer 20w guitar amp!  I just tried it out and wow!  It only has as much clean headroom as any other 20w amp, but its plenty for practice.  Crank it up and throw on a distortion pedal in front of it, and damn!  Very much loud!  I wasn't expecting it.  But I guess it makes sense, with the right speaker even my 15w dean markley gets pretty loud.  Anyway, it would make a sweet practice amp power chip if someone is interested.  Brian is suppose to start selling PCBs for the lm1875 soon also, so you won't have to make your own or anything.
Schematics and Layouts / TDA2003 practice amp
April 02, 2006, 06:43:12 PM

There is an easy to put together kit for this too:

I found it to be ok with guitar, but very poor with bass.  Quite frankly I like the Little Gem better though.
Amplifier Discussion / TDA2003 bass amp
April 02, 2006, 06:40:30 PM
Well, my brother wanted a small bass amp, so I figured a TDA2003 circuit would work well...well, no.  It sucks actually lol.  Virtually no useable clean headroom, I would dare say the lm386 is better.  Its no looker either lol.

I should say that it worked pretty well with guitar.  However, I like the lm386 better even though its not as loud.
Preamps and Effects / Lets design a preamp!
March 31, 2006, 01:20:51 PM
Ok, so we are going to base this thing off from the K-20X preamp because its simple and has great tone.  But, we are going to ditch the OD for simplicity's sake, plus then people can add their own OD later, and we are going to add a buffer to the front.  Anyone want to throw up a quick schematic of their best idea for it?  If we get this thing looking good, we can get some PCBs printed up with on them and sell them for cheap.
Schematics and Layouts / Little Gem
March 31, 2006, 10:45:52 AM

Thank you!
Amplifier Discussion / My little gems
March 31, 2006, 10:44:20 AM

My first little gem.  It runs on one 9v and is in a cheap treasure chest that I bought for $2 at a dollar store.  The 1/8" jack isn't a headphone jack, but an external speaker jack for my pot cab.

Here is my little gem clipper.  I can hook it onto my pocket and walk around playing guitar in my apartment.  No volume control, I just use the guitar's volume...and leave it all the way up anyway.  The switch on it goes from clean to OD.  It runs on 3xAA.

The schematic is available at and in the schematics section of the forum.
Amplifier Discussion / My lm3886 power amp
March 31, 2006, 10:23:49 AM

The schematic for this is in the schematics section of the forum.
Schematics and Layouts / lm3886 amp
March 31, 2006, 10:18:55 AM

**Taken from the lm3886 manual @**