A modest 2 to 5 watt unit can be constructed using a single IC and a handful of components. However, I thought that if I’m going to the trouble of making one, I may as well do it right.
The picture shows the front panel of the final unit. It contains a pre-amplifier, a three-band graphic equaliser and a power amplifier delivering around 5 watts maximum into 8 ohms.
There are some switches on the front to allow for bypassing the pre-amp and graphic equaliser and some other basic functions.
The unit contains its own internal mains power supply and as you can see, fit’s in a nice small foot-print. There is a socket on the back of the unit to drive an external speaker.
The unit was constructed with what I had available to hand; including the case, and made a nice weekend project.
If people are interested in the design, I'll publish details.
Another new piece of equipment I’ve invested in is an anti-static bench mat from Rapid Electronics.
Now, I’m not one of these static paranoid people that seem to flourish in the electronics world. I’ve never damaged anything with static; that I know of, but I’ve always taken “sensible” precautions like wearing an anti-static wrist strap when poking around with sensitive components.
However, when I built my workshop, I opted for the cheapest worktops that I could find in the required quantity, which turned out to be in a nice grey granite affect. Unfortunately, I’ve started to notice that as my eyes are getting older (and I now wear glasses for the first time); it’s harder to see some components when placed on the worktop.
I’ve opted for a mat in light blue measuring 900 x 610mm and it’s just about perfect for the job. It provides good colour contrast for components and I even managed to find a couple of SMT capacitors that I dropped; the little buggers blend in perfectly with the grey/black granite affect worktops and are almost impossible to find.
They are available in several different colours and sizes and each mat has 4 earth bond press-studs; one at each corner. You can connect one stud to an ESD earthing plug, and then you can connect a wrist earth strap to another. You can also lay several mats down to cover larger areas and connect the mats together using jumper leads. They are also pretty robust, clean easy and seem to resist molton solder; so far.