# DIY amp worklog



## drf (Oct 22, 2006)

first a warning: I tend to be awfully slow when it comes to home projects, this is partly to do with being poor and mostly to do with having a family and little free time.

The goal:
I wanted to build an amp that could be very cheap and easy to get together, use easily sourced components and also be upgrade in increments until it was as good as if not better than comercially availiable offerings.

I am quite aware that this may not be cheaper than buying a "made in asia" unit, however the challenge here is more for satisfaction and the ability (hopefully)to inspire people to have ago at there own.


I started with tracking down a design that would fill the above requirements, I found it at Rod Elliots site:
http://sound.westhost.com/project3a.htm
For copyright reasons I will refer to the above link instead of posting his schematics. For those who want to build this amp but can't or don't want to etch there own PCB then you can order circuit boards from the ESP site. Rods' circuit boards are very well layed out and are reasonably priced. <-- I strongly recomend this if you haven't etched boards before.

While I am designing the circuit board I started work on the case.

the cheapest way to house any DIY electronics, I have found, is in old PC cases.

In this one I have Covered over the drive bays with a piece of aluminium-clad plexi and bogged it smooth. I am not very happy with the finish so I might take the entire front of and get a piece of aluminium cut to size.









At the rear I have cut out the expansion card slots and cut a piece of aluminium to fit, I then cut a hole large enought for a 80mm fan which is mounted on the rear of a PSU case. The old PSU was cut down to leave the mains plug and fan, I have added to this a mains fuse.









On the inside you can see there is still the vertical wall that was used to house the CDROM and HDD, Here I am using this as an EMF shield for the transformer. This transformer I have salvaged out of an old Sansui amp, it is capable of supplying about 220VA which is more than enough for the 50Watts/ch. it will be powering. Also the heatsinks where salvaged from a 100watt amp. there is no real nead for the fan on these heatsinks, considering that each HS is only dealing with 50W output devices. the reason I installed the fan was because of the low air flow in this case and the possibilty that down the track I might use it for a more powerful amp. 









next: hopefully will be etching the PCB's

As usual all comments questions or suggestions welcome 


cheers 
dr f


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## F1 fan (Jul 6, 2006)

Great stuff drf,thats real DIY when you get out the ferric chloride and etch your own boards.I will be watching your progress with interest.
Rod Elliots site is a goldmine of info for diy'ers and I have built a version of his EAS project #48.


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## JCD (Apr 20, 2006)

Seriously hard core if you're going to be doing the etching yourself! :clap: 

Well, I'm looking forward to following your progress.. fast or slow, no matter to me. I just wish I had more knowledge to offer -- this kind of electronics is way beyond my pay grade.

JCD


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## drf (Oct 22, 2006)

well having time of I am moving a little faster on this project than I had tought I would.

Got the PCB designs done and printed onto photoglossy paper. Here I have cutout a piece of paper and taped it to the ordinary paper as my PCB software only prints in the centre of the page and I didn't want to waste and entire sheet of photo paper for one 85x60 mm PCB.









After cuting the blanc circuit board to size I then fliped the photo printout onto the board then using the iron transfered the laserjet toner to the circuitboard. NOTE: if you do this make sure either the paper does not release resins or use an old iron. If the other half decides to iron her favorite dress after you have etched a circuit board there could be trouble.







after the toner has been transfered I left the boards in a bucket of water to soften the paper so it would peel away and leave only the toner. 
Soaking the PCB is just the right amount of time for a nap, or to go a buy a new dress for your wife.


After the paper has been removed it is time to touch up the places were the toner did not take to the board (the bottom lefthand corner was bad), I did this with the PCB marker.







Now to the point of no return, by this I mean asking the better half for one of her clear pyrex baking dish lids, She said yes :jump: . Into the ferric chloride and hold it over the 500W lamp whilst lightly agitating it. 







20min later I have 2 PCB's, these I have already drilled and are now ready for the components.
Sorry for the quality of this last shot, the camera didn't like the shine of the copper.


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## F1 fan (Jul 6, 2006)

Great looking boards:T are you going to bath them in some liquid tin?

hehe I steal all my etching tanks from the kitchen also and somehow they just never make it back there.:bigsmile: 

btw.I think the surround on that speaker in the pic needs some attention.


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## drf (Oct 22, 2006)

Didn't know about liquid tin, Hmmm. This is only the second time I have made PCB's this way.
I will look that up and give the next one I make a coating and see if it helps. One thing i noticed about this method (other than being the cheapest way) is there are occasionaly sections of track where solder refuses to take, I assumed it was were the toner was not fully removed but need to have a closer look. 

do you really think the surround is stuffed? I was just going to replace the dustcap :joke:


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## F1 fan (Jul 6, 2006)

Maybe your electronics supply store carries the Liquid Tin made by M.G. Chemicals it comes in small 8oz bottles.It is easy to use and looks great plus protects the copper from oxidation.I usually give the copper a light polishing with fine steel wool before dipping into the tinning solution.


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## JCD (Apr 20, 2006)

First off, that is wicked cool -- nerdy yes, but that's a good thing.

Second, how much would you say the supplies for something like costs?

But really, wicked cool.

JCD


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## drf (Oct 22, 2006)

In Australian $ so far to make the PCBs including etchant, papers about $40. but the thing is i can now make another board for less than $5 (cost of blanc circuit board) because you only use 1 sheet of photo paper and enough etchant to cover the board. 

Because I am using the cheapest parts to get it up and running I expect the total cost of parts would come to less than $150 including transformer, output devices and filter caps. 
In reality becuause I have built 1/2 dozen amps before and hoard old amps I have enough parts on hand that this unit will cost me next to nothing. once the unit is running over time I will swap out the cheap parts for Higher grade parts.


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## drf (Oct 22, 2006)

update:

I have finally got around to populating one of the boards. 









The more components I place on this board the less I am happy with the layout. I will persist though and get it working, then I when I am happy with my understanding of the circuit I will design a new board and get some better transistors.

I had a look around for liquid tin, but none of my suppliers have it, It may be under a different name here or something but I will worry about that for the next board I do.


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## HionHiFi (Feb 18, 2007)

Great looking project. I too am planning one day to start my first DIY amplifier project. Why with digital amplifier chips in such cheap supply why not.


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