All amps at the mo’. Read up a little on the TDA2003 and realised the one I’d made was sorted to amplify at 10x but others were using them at 100x so I changed a resistor, divided by ten, and it’s doing everything as it should.
But this small interval between having it not really work to having it work had me designing another one but using a tube… actually I think I wrote about this yesterday… but suffice to say I designed up an amp then went out and found nearly all of the parts I’d need, measured a speaker and found some wood for the box then cut out some aluminium for the electronics to sit in. My plan was to try and make the amp from scratch in one day… but I didn’t make it but I did get this far.
Oops, left the camera plugged into the PC so the batteries have drained again and need charging and it never came with a power supply to run it on 3V. (later on…)
So it’s two stages of tube amplification which is the same as any fender amp from the Golden era then into a j-fet set up as source follower to drive big muff style tone stack, which I suppose I should allow to be bypassed by a switch, then into the TDA2003 at 100x amplification.
I was going to do one of those step by step things, photo essays, pic of the parts, the sheet of aluminium and the plank of wood for the box, the alloy cut and marked, then drilled filed and folded but the camera was on charge… well the batteries (as they are now), so I did it all to the stage of folding up the enclosure and mounting all the hardware.
Today I’m going to make up a small jig of sorts to wire up all the pots to the tag trip and tube base simply because once the chassis is folded it’s really hard to get the stuff soldered up in situ.
The plank is a bit of something or other, an exotic softwood grown here that I picked up in Patamahoe years and years ago and still have enough to make a box and sides. Almost blood red is the wood, so yummy, The speaker is a 12″ alnico magneted Plessey NOS with paper cone and ribs which I also got years ago from a guy in Christchurch. I bought a whole bunch of them for about 10 bucks each and put four in a quad box. Those four sound the best and feature the ribs only around the middle circumference of the speaker cone. The ones I have left, theres three, are either completely without ribs or have ribs all across the cone face. I’ll dig out the other two and use which ever I only have one of for this amp and save the other two for a duo tub at some stage.
I think also that I’ll do a line out on this amp and have a 9V out for fx. The line out will come in handy if I want to do a psuedo stereo thing and maybe send mono signal to this amp then maybe a tremolo into another one.
Always more ideas! Even this morning I thought about doing something with speakers along the lines of the last one in the barbecue tub, the 15″, simply because when I picked it up to move out of the way to photograph the amp chassis, I placed the big speaker tub on top of a frying pan lid and immediately thought that I could suspend a smaller speaker in that… my brain then goes off into the ramifications of crossovers, active or passive?, and how neat it would be to have a whole bunch of different sized speakers suspended in various containers and the whole bunch sitting in a sprung frame so the speakers could flop and jiggle with the sound it emits.
Some chap asked a question about multiple speakers a month or two ago on DIYstompboxes and the consensus was that many the same in series parallel combinations, so it stayed at 8 ohms or whatever, was entirely feasible as long as the wires to the speakers weren’t too long and inductive capacitance became an issue… or was it reactive capacitance. Something beyond my ability anyways that simply means long cables need more power to drive and suffer treble loss which is why systems in buildings, intercoms etc, sound tinny and obscure beyond the cheapness of the speakers… even though they ride the signal on a 50VDC carrier.
I’ve already got unfinished stuff in the pipeline that I’m losing interest in as well as a few projects almost completed that I have almost completely lost interest in and I’m now I’m thinking of a radio tower of speakers in sprung shells. Ideas are always fun to play with and often bringing them to reality and the trouble is often brings can be even more fun!
It would be far sounder physically (sounder as in mechanically sound and physically in regard to physics) to suspend the speakers as I have with wire in the openish enclosures but to then add springs, one or two from above and one behind, from the enclosure to the frame.
It’s kinda is making more sense to me because I’ve got absolutely loads of interesting speakers and an active crossover I made a few years ago that was going to be part of a monitoring system for some PC recording.
One more big bit of furniture to store somewhere though but I do have to work up some significantly aesthetically pleasing pieces that bridge the gaps between furniture making, sound sculpture and plain old art to get photos to send to the Pollock Krasner Trust over in NY next year so maybe this is the thing to do?
Then on the back of it I could suspend a reverb plate, ala Felix the incomparable, so the reverse thrust of the speakers, through the ports on the rear, is picked up and fed back into the system… Shit Bro, I want One!