Author Topic: Home built Amplifier  (Read 4502 times)

Offline ibuildstuff4u

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Home built Amplifier
« on: January 05, 2014, 06:24:06 PM »
I just finished my Chip Amp and it sounds great. I was shocked at the bass that this little amp puts out and it's quite loud too! I'm running a pair of Bag End PA speakers in my workshop with 12" woofers and a compression tweeter. The speakers are big, but are very efficient and the amp is able to drive them just fine. The amp runs cool even at full volume.

I started off this project with an amp I found at a local Pawn Shop for $40. I bought it knowing I was going to take it apart and use it for the case and I thought the price was pretty good for what it was. As a bonus it had a 18v + 18v transformer inside! It's only rated for 1.8 amps, but I figured I would give it a try and replace it if needed. I also tried a 29v + 29v transformer with a lot higher VA rating and there wasn't much of a change in volume, it just created more heat from the chip amps so I'm keeping the smaller transformer inside.

The case also had some nice LED UV meters and I had to reverse engineer the original amp circuit to figure out how to hook them up with the new chip amps. I had to pull some resistors and diodes off the old board to run inline with some of the connections for the UV meter and simply soldered them to the wire and covered them in heat shrink tubing. If you look closely at the top of the chip amp boards you can see where I had to solder a wire on to the speaker outputs to steal the signal to trigger the UV meters. It ended up working out great and everything works as it should.

As for the case I was able to reuse a lot of the original parts, but changed out the heat sink for a larger one and also added new jacks to the back as the original ones were really cheap. The holes for the original jacks were really large so I covered them up with a piece of carbon fiber I had laying around and drilled new holes.

The first two pictures are of the original amp, and No it didn't put out 1000watts, not even at 2 ohms bridged. It didn't sound good ether so I didn't feel bad about trashing it for the case.

Dale P.

Offline ibuildstuff4u

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Re: Home built Amplifier
« Reply #1 on: January 05, 2014, 08:07:52 PM »
My next project is a 100watt @ 8 ohm mosfet amplifier.  This will be just a mono amp and will run a subwoofer for the work shop. I tested the board today and it works good and seems to have a lot of punch and ran super cold.  I may even scale back the heat sink after I some more testing.

The PC board was etched by my brother and it turned out really nice.  The amp design is a NMOS 200 amplifier.

Dale P.


Offline Brass_Machine

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Re: Home built Amplifier
« Reply #2 on: January 05, 2014, 09:22:58 PM »
Dale,

On your first amp... did you replace all the insides? Self designed circuit and did you use/modify one off the interwebs? How does it sound?

How did your nephews speaker turnout? (on a side note, my two nephews have come to me with projects...)

I am slowly reigniting my interest in DIY audio.. I have you to thank for that...

Eric
Science is fun.

We're all mad here. I'm mad. You're mad.

Offline ibuildstuff4u

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Re: Home built Amplifier
« Reply #3 on: January 05, 2014, 11:57:20 PM »
First of all the top hat speakers are NOT done yet.  I have both of the top parts done and an waiting for my nephew to make the rest of the wood parts.  He is in an after school club that builds robots to compete against each other and it takes up a lot of his free time so I have a feeling that the top hats will not be done for several more months. : (

As for the first amp, I gutted most of the old amp and only re used the transformer and the front mounted LED UV meters as well as the main power switch, power cord, and fuse holder.  I put in the two chip amp boards, larger heat sink, power supply board, and rear connectors. The amplifier boards came from chipamp.com and they are a really easy board to solder up and use.  They put out around 55 watts and sound really good.  I'm pushing some pretty large speakers with the amp and it stays cool under full power.  I think I'm going to install a larger transformer soon as the one that came in the case has a really low va rating, but for now it's working great.

Next up is a DX blame Supercharged amp build.  I bought some boards a while back and recently ran into a case that will work out pretty well for the two boards.  I still need to order all the parts as well as a transformer so it's going to be a slow build but I will post a few picts any way.  I also have boards for a DX Blame Destroyer amp that puts out 250 Watts per channel @ 8 ohms but after pricing out parts I realize that they may never be finished as it will cost around $500 for all the parts needed!  I will just hang on to the boards and every time I order parts for something else I will add a few extra parts for the amp.

What type of projects are your nephews asking you to do?
Dale P.



Offline ibuildstuff4u

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Re: Home built Amplifier
« Reply #4 on: January 06, 2014, 12:06:44 AM »
The funny part is I have a QSC RMX 800 PA amp that puts out a REAL 200 watts @ 8ohm running a pair of Bag End PA speakers for a 10' X 10' work shop but yet I still find my self wanting more!  What are all the amps for?  Who knows, they are just fun to build and see what sounds better.  Do I really need a powered sub for the shop? NO, but will still probably build one this winter.  It's just a fun and addicting hobby, so I'm sorry Eric if I got you involved again : )

Dale P. 

Offline John Rudd

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Re: Home built Amplifier
« Reply #5 on: January 06, 2014, 03:31:29 AM »
 :doh:d
My next project is a 100watt @ 8 ohm mosfet amplifier.  This will be just a mono amp.

Dale P.
Do you have the circuit diagram to share please?
eccentric millionaire financed by 'er indoors
Location:  Backworth Newcastle

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Offline ibuildstuff4u

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Re: Home built Amplifier
« Reply #6 on: January 06, 2014, 08:40:01 AM »
The amp is called the NMOS 200.  Here is a link to the site with all of the information.
https://sites.google.com/site/quasisdiyaudiosite/nmos-series/nmos200-1

My brother also made me up a stereo PCB for the NMOS 200 amp and I have it 99% done, but am missing a few parts for it.  One of these days I will have to place an order to mouser for a bunch of parts.

The amp in the picture is the DX Blame MKIII Destroyer.  This is NOT my finished amp, I have the bare boards and hope to build it some day but with 10 transistors per board it's going to be pricey to build.  The eight large caps (four for each board) are almost $100 to buy.

Dale P.

Offline Brass_Machine

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Re: Home built Amplifier
« Reply #7 on: January 12, 2014, 05:21:23 PM »
...

What type of projects are your nephews asking you to do?
Dale P.

The oldest wants me to do some carbon fiber fab work for his car. Wants to replace a bunch of body stuff. Wants help designing a CAI\Ram air for it...

The youngest wants some case mods done for his PC.

Have you done a tube amp yet? (sorry if I already asked you this)

Science is fun.

We're all mad here. I'm mad. You're mad.