"Micro-S" Terminal Cup Stereo Amplifier

[Navy Guy]

Re: "Micro-S" Terminal Cup Stereo Amplifier

Really cool project Tom!

[carlspeak]

Re: "Micro-S" Terminal Cup Stereo Amplifier

Very nice job! But what does the switch do? On/off? or something else?

[tomzarbo]

Re: "Micro-S" Terminal Cup Stereo Amplifier

Very nice job! But what does the switch do? On/off? or something else?

Yes, it just turns on/off the power to the amp. It cuts the positive lead.
I have another amp/terminal cup to do another one of these on... I plan on removing the switch from the terminal cup and switching (get it?) to an LED lighted rocker switch that can be mounted to the front of a speaker. You will be able to see if it's on that way and turn it on/off without feeling around the back.

TomZ

[tomzarbo]

Re: "Micro-S" Terminal Cup Stereo Amplifier

I worked up another of these small terminal cup amps using the same amp board.



It's basically the same but I removed the on/off switch from the terminal and moved the input and power-in connections to the edges of the cup.
The switch has leads that would be soldered to the leads coming from the amp board. The switch just cuts the (+) positive current flow, and has a copper looking terminal for connecting the (-) negative line to so the LED in the switch will light.



Since I don't have a set of speakers to try this out in yet, I've soldered lines to the switch and amp to make switching things around easy until this finds a permanent home.
I bought parts for a set of Jeff Bagby's Quarks to try this amp out in. It would be a perfect candidate I think. Both are pretty tiny and I think the watt output of this amp matches most small speakers well.

More pics:



The Potentiometer is connected to a small piece of flexible clear plastic tubing (1/4" inner diameter)... A few wraps of electrical tape made a snug enough fit on the pot shaft. Then a piece of 1/4" dowel became the extended pot shaft capped off by a spare knob I had from previous electrical madness. A slice of wooden dowel with a 1/4" hole drilled in it would work fine too. That's what I was going to do until I found these spare knobs.



Again, a zip-tie was looped, clipped, and super-glued to the back of the terminal cup to provide a stronger connection point/strain relief for the two wires that will connect to the crossover feeding the speakers inside the cabinet.

So basically, the parts list would be the same except for deleting the toggle switch and replacing it with a lighted rocker switch like this one: http://www.parts-express.com/parts-e...d-12v--060-770

It has a 12V ready LED in it. Just drill a hole in the front of your speaker cabinet, solder the leads on, goop it in with caulking, speaker caulk, etc.

********

Here's the same potentiometer/rubber tube/wooden dowel/knob treatment applied to the first amp...


It should make adjusting the volume easy, just feel for the wires exiting the cabinet and the volume knob will be between the wires. The rubber tube part could be made longer for more finger clearance... it would droop a bit, but that's no problem.... or you could just leave a length of 1/4" dowel back there to act as the knob. That would work fine too.

When I get the quarks put together, I'll post some pics of that setup.

The only thing I can think of to add would possibly be a fuse somewhere in the mix. A built-in holder like this one: http://www.parts-express.com/littelf...older--071-510 would work I think. If you moved the super-glue'd wire tie-down point further down to where it goes on an angle there would be room for the fuse holder on the panel next to the amp board.

I'm not sure what amp fuse to put in it, or if it's really even needed. Maybe others more experienced could chime in here... The board doesn't have a fuse on it that I can see. If I were to give this to a friend, I think I may want to add a fuse just to be safe since there will be electronics inside a sealed wooden box and things do sometimes go wrong.

Anyway, this has been fun to mess around with and I can't wait to get them installed in some speakers to see how they do built-in. I have a few small speakers that this amp would work well with, some with this exact terminal cup, but they all have my usual crossover-on-a-stick treatment...



So I guess I need to make a new set...
More to come...

TomZ

[Chris Roemer]

Re: "Micro-S" Terminal Cup Stereo Amplifier

That's just too cool Tom!

[tomzarbo]

Re: "Micro-S" Terminal Cup Stereo Amplifier

That's just too cool Tom!

Thanks Chris!

Any thoughts on the fuse situation? The more I think about it, the more I think it's probably a good idea.

I just don't know what value to put in there, or what could go wrong to really need it. I imagine that if one of the solder joints came off and a wire touched something else on the board, that could be a problem; possibly cause sparking or something.

Heat from the amp section I'm not worried about, the chip/amp appears to be made out of some magic substance that amplifies sound without generating heat!

This fuse is 3 amps: http://www.parts-express.com/littelf...5-pcs--071-660
I think a fast-blow fuse is in order, but I don't know what the amps should be, maybe 5 amps would be more in order?

Not putting you on the spot Chris, anyone who knows more than me about this could chime in, which would be just about anyone!

TomZ