The PowerMan


Schematic (prototype)            PowerMan page            Samples            Home

UNDER CONSTRUCTION


The PowerMan is going to be my first "found" project - the speaker and box are salvaged from dead computer equipment.

The speaker is the subwoofer from of a set of PC speakers. It just so happens that it mounts perfectly in the hole left in the box after removal of the dead fan – even the grille fits (with standoffs – that speaker has a large excursion).

So now the question is what to put inside such a cute little box...

Last week I bought some 6021W "subminiature" tubes from Adam Alpern , who bought a large batch after discovering Zachary Vex's 1/2 Watt Nanohead . One of these will provide 2 triodes for the preamp and the other will be used in a self-split push-pull configuration.

One of the problems with these little tubes is that they have leads instead of pins, which means that they can't be socketed securely. My solution for now is to mount them on perf board, with 3-pin headers for each of the triodes and a 2-pin header for the heaters. Until I have all the circuit values I like worked out I'll just clip test leads to the headers, which should save wear & tear on the tubes. If it holds up reasonably well, I may just save this board for prototyping other 6021 projects...

[07 March 2003] OK, so now I've got a prototype assembled, with pots in positions that are likely to need tweaking. A couple of months ago I got this bench power supply off eBay, so I can hold off on the power supply part of my design until I know what the rest of the circuit will be and what voltage(s) I want it to run at. Last night I only got to the point of powering the filaments – tonight we'll see if this mess can push a speaker...

[09 March 2003] After a couple of evenings of tweaking pots I've settled on the circuit values for a basic design with volume control only. I still want to do some calculations, but I'm leaning toward running the output tube hotter than the specified maximum (about 0.8W per triode, as opposed to the spec of 0.7W). The preamp has lots more gain than I feel I really need, so next I'll be playing with inserting a one-knob tone control...

[22 March 2003] I've found that it sounds hugely different with different speakers, so I'll have to figure out how (or whether) to deal with that. Looks like I've got a 2 week wait for my power tranny, too.


Schematic (prototype)            PowerMan page            Samples            Home

Copyright © 2003 Mark Lavelle. All rights reserved.