Introduction: Easy Amplifier

I've been meaning to make an amplifier for the back room for a long time. This project finally kicked off after finding some Sony bookshelf speakers on the side of the road and the Instructables competition for hand tools only, well that's the sort of project I'm qualified for.

I had bought a Tripath amp PCB a few years ago, along with a power supply, some speaker binding posts, RCA sockets, plugs and switches ect. All of these items then got moved from box to box and finally to the back of the shed. After much searching I finally found all the bits I needed to get this project going.

Step 1: ​Tools Used:

Dremel - Router attachment, 3mm Cylindrical Bur & Cutting wheels

Plunge router - 45 degree bit

Mini rip saw

Cordless drill - Selection of drill bits

Bench clamps

Soldering iron

Eye glasses & ear protectors

Step 2: Enclosure Construction:

I have had an idea for this amp design for a while and I like the way you can bend aluminum composite panel

First check the panel is square, I was hoping that I would get away with not having to square it up but it was not square (it is an off cut).

For this you can use a router or as I did my mini rip saw.

Now the real fun begins. Setting up a jig using bench clamps and a strait edge (3mm aluminum bar works well for this) at 90 degrees from the side of the sheet.

Now we nearly ready to cut our first channel. First set the height of your Dremel so it mills all but the last .5mm of panel. This isn't as hard as it sounds but you may want to try the depth out first on a off cut.

Because aluminum composite panel has a plastic core you will need to run the Dremel up and down a couple of times to clear out the melted plastic. Once done you should have a channel that is clear of debris and still have about .5mm of plastic and the aluminum outer skin still intact.

My side panels are oak off cuts and are 50mm tall so I need to allow a 50mm section which will become the front of the amp. This means I need to mill my second channel 50mm from the edge of the first channel so I can bend the panel around the oak side panels.

The last job is to trim the finished panel down to size.

VERY IMPORTANT NOTE: aluminum composite panel comes with a protective film on both sides. I took this off what will be the inside of the box before I had finished working the panel. As you can see when I cut the end of the panel down to size I scratched the paint off. Luckily it wont be seen.

Step 3: Enclosure Assembly:

I wanted as clean an enclosure as possible so I decided on only four screws to hold it together, two on the top and two on the bottom.

I also wanted the screws to be counter sunk. I haven't had a lot of success in the past with countersinking screws. With a hand drill the countersink bounces around and gives an irregular shaped hole, internet research suggests its not really possible to get a good smooth finish without a drill press.

So what to do……… Then it stuck me. I have a plunge router, so using a 45 degree bit and adjusting the plunge stop so not to go all the way through I was able to make perfect counter sunk holes for my screws.

The last thing to do was to bend the front of the enclosure around the oak side panels and screw it all together. First I screwed the oak side panels to the top panel then with these securely in place I bent the composite panel around the wood and finally screwed the bottom lip to make the top, front and sides of the box.

Step 4: Enclosure Bottom Tray & Back Panel Assembly:

The bottom tray has no bending, its simply a square piece if composite panel with countersunk holes in the four corners, feet and the brackets to hold the back panel in pace.

I drew up the back panel with marks for were I wanted holes for the binding posts and RCA plugs. I then printed it out on self adhesive sheet, cut it out and stuck it down. I carefully drilled the holes and cut the square hole for the power socket using a Dremel with a cutting disk. At this point it looks a bit rough but when you add your sockets and cover the torn edges it looks pretty smooth.

Step 5: Setting Out the Components:

With the back panel assembled its time to lay out the position of the amplifier components, not really much to say here, just mark the holes, drill add stand-offs and screw together.

Because the amp PCB had the volume pot on board I had to remove it so I could mount it on the from panel of the enclosure. Unfortunately the pot broke whilst I was desoldering, fortunately I had a spare. it was bigger and as it turned out easier to fit. I soldered lead wires to the new volume pot, soldered wires to the RCA plugs and speaker binding posts, attached wires from the mains plug to the power supply and switches.

Step 6: Front Panel:

I only wanted two switches on the front. One is to be the volume the other to be the power.

I had in my parts box two power switches the clear green I want for the power switch the black I will chop up and make into a matching volume control.

I marked out the central line of the front panel, decided were I wanted my switches and marked and center punched for drilling with a 22mm spade bit, this worked well and left a clean hole.

Step 7: Volume Control:

Next I cut up the black switch to become a volume knob, I found this particular type of switch didn't come a part.

So using a pen lid and shaping it to fit the inside of the switch and a small volume knob that fitted in the other end of the lid I was able to hot glue the assembly together to give my what I needed.

An aluminum bracket was made for the volume pot and the assemble was screwed into position.

Step 8: ​Final Assembly:

Nearly there, last few screw to secure the whole thing together and we are done.

Step 9: ​Final Thoughts:

After all the excitement of getting it together I turned it on only to hear absolutely nothing!!!!

If any of you had noticed from the pictures I had neglected to wire the power supply to the amp, this wasn't such a big deal even though I had cleared away all my tools for the day, it was just a screw terminal and plug.

So after putting it all together for a second time, I can say I'm very pleased with how it turned out, but there is a minor change I would like to make.

I would like the green power switch to be lit when on, so I need to figure out how to get an LED in there, shouldn't be to hard.

Step 10:

Comments

author
oululife made it!(author)2016-04-21

Oh, sooo many years ago I built a pretty high-powered stereo amp. So long ago, that it used a Quad (UK company - the best!) pre-amp.

It used PCB's from an Elektor design - FET's for output. About 100 watts RMS per channel
My God, did I put some grey matter and design into the power supply.
It was linear, therefore quiet (but HOT!!!), but the most important thing was the grounding. It used "Star-earthing".
See it explained at http://www.lh-electric.net/tutorials/gnd_loop.html
Believe me, I was horrified when, 15 years later one of the base-station designs I worked at, at Nokia suddenly developed an FCC-regulation-killing spike at 55MHz from the carrier. Saw it on a Spectrum Analyser, immediately recognised it as the Digital Signal Processor's clock frequency.
Turned out some University 'educated' toe-rag had redesigned the (carefully designed) motherboard, and tried to save a bit of money by commoning RF (Radio Frequency) and digital grounds.
I had the benefit of skipping university, and thus actually learning to do stuff, rather than to be told. So I spotted the stupid mistake in a minute.
Cost me all my Easter holiday - even sleeping on the lab. floor on Good Friday - to fix it.
Cost us several hundred thousand dollars in lost production. That was in 1998.

author
Dwargh made it!(author)2016-04-21

Great work! Its design is so simple!

author
EmmanuelI8 made it!(author)2016-04-20

I didn't see any component diagram?

author
JeffH163 made it!(author)2016-04-15

Excellent amp build! The bent edges on the enclosure came out real clean!
Makes me want to try to do it.
So far all my amp builds have been in wooden cases.

author
crispndry made it!(author)2016-04-16

Thanks for the message, I'm really pleased with how the bent edges turned out. This is the second project I've used this style of case on and it was much easier the second time around.

author
voblak made it!(author)2016-04-16

Two mistakes from electrical POV.

1. Never ever, ever use switching PSU for amplifiers, they just bring too much noise in the system.

2. Add cca 4700uF capacitors in the power line. This helps when the bass kicks so your power line doesn't collapses and also the switchers aren't big fans of fast changing current

author
crispndry made it!(author)2016-04-16

We don't listen to this amp loud, its for background music so no need for extra caps and I really don't notice any "noise" in the music. Thanks for your thoughts though.

author
Trickynekro made it!(author)2016-04-16

Most switching power supplies operate somewhere between 75 - 300kHz range, with some going even higher. You can not expect to ever hear the switching, but if you are still concerted about it, you can use the stable frequency PWM onces and some proper filtering.

author
kennycheung made it!(author)2016-04-15

I appreciate the part of enclosure construction. It's the most difficult for me. Thanks for your demonstration!?

author
Extremetasks made it!(author)2016-04-12

Nice build ! one thing I would suggest is some venting slots

author
crispndry made it!(author)2016-04-13

Thanks, I did consider vents, but at this stage I'll see how warm it gets.

author
JoshB4 made it!(author)2016-04-12

I’d appreciate a parts list which includes everything used in the project, including the amplifier, power supply and knobs.

author
crispndry made it!(author)2016-04-13

Thanks for the reply, I bought most of the components from ebay years ago, other bits were salvaged.

author
desidude52 made it!(author)2016-04-12

Nice instructions for the enclosure. Can you mention details of the components you used? Which model amplifier and power supply and costs? Thanks.

author
crispndry made it!(author)2016-04-13

Thanks for the reply, I bought most of the components from ebay years ago, other bits were salvaged.

author
PhamH23 made it!(author)2016-04-12

Nice amp. How to print text on back plate?

author
crispndry made it!(author)2016-04-13

Thanks for the comment, I printed on self adhesive paper cut it out and stuck it down.

author
RickO8 made it!(author)2016-04-12

Nice job!
Suggestion.....
It is hard to tell but it looks like you didn't use shielded wire between the volume control and the pc board. Any time you have an audio path (not speaker output) like that you should use shielded wire to reject noise.
Cheers

author
tasios made it!(author)2016-04-12

Not to contradict you because I would prefer shielded as well, but it looks like the volume pot wire is twisted. Twisting wire rejects noise too, which is why Cat5 (and higher) network cable is twisted. But I agree, in a low volt audio pathway like that I would have personally used shielded as well.

author
crispndry made it!(author)2016-04-13

Thanks for the comment, yes the wires are twisted, but I'll bear that in mind about shielded wires for future projects.

author
RickO8 made it!(author)2016-04-12

Thanks for the reply. Yes twisted as in cat5 is good for rejection in data. But for audio especially near a power supply should use a braid shielded wire.

author
skyline1 made it!(author)2016-04-12

Yes twisted pairs are only really effective with differential (Balanced) signals where the interference (common mode) signal is the same in both wires and cancels itself out

author
skyline1 made it!(author)2016-04-12

Or shielded twisted pair with the braid connected at one end only

author
crispndry made it!(author)2016-04-13

Thanks for the comment, as tasios pointed out the wires are twisted, but I'll bear that in mind about shielded wires for future projects.

author
ccguelph made it!(author)2016-04-12

If you were thinking of building something similar again I would suggest looking into switches with inbuilt LEDs. They make some really nice ones, and saves A LOT of hassle of having to also wiring and LED, I speak from personal experience :/ Its basically just a switch with an extra power input...

author
crispndry made it!(author)2016-04-13

I would next time, I assumed the clear green switch had a lamp in it, it was only after closer inspection I realised it didn't.

author
ccguelph made it!(author)2016-04-12

Just because you mentioned wishing the power switch would light up when on...

author
PhilS43 made it!(author)2016-04-12

Nice looking amp.

Reminds me of my first "proper" amp in 1975 made by Cambridge Audio. This had teak end panels and aluminium top and bottom. Way back then, we were spoilt for high end amps, all nicely engineered - Ferrovox was an example. Finishing touches were things like socket cap screws in black or stainless and classy knobs etc. Neutrik or Lemo do good connectors

author
RonB50 made it!(author)2016-04-12

Nicely done, especially without a shop full of tools. I like it.

author
zappenfusen made it!(author)2016-04-12

Translation?

Nice box.

zapp

author
zappenfusen made it!(author)2016-04-12

Translation?

Nice box.

zapp

author
zappenfusen made it!(author)2016-04-12

Translation?

Nice box.

zapp

author
SantaB made it!(author)2016-04-12

I think the title should be "Easy Amplifier Enclosure". You don't really talk about how to build an amplifier, but simply the enclosure, and how a pre-made amp fits inside it.

Regardless, nice job on the steps and info on how to build and drill a box from scratch.

author
pepelnyyp made it!(author)2016-04-12

Напишите, пожалуйста, пару слов об использованных компонентах.

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