I like it. Have something similar in planning but cant find a suitable amp module anywhere. Are the 2 pots on the front volume lvl for left/right or tone control?
Nice You could screw the back in, no brackets, just predrill, run silicon along the joins, and fit the back which has been countersunk slightly & use long self tapping wood screws. It won't be that hard to disassemble, whilst being very solid. Don't forget to seal the openings in the speaker boxes where the wires exit, using silicon or some sort of filler. You should also fit a grille or just drill plenty of holes in the bit of wood that covers the amplifier compartment, or it would be a chamber that gets hot = reduced amp performance & lifespan.
The problem with that though is that I have found with this MDF that self tapping screws go in once, come out once, and the hole is done. I need it to come apart a good dozen times before things start failing. I'm thinking of using the brackets, but permanently attaching the nuts to the brackets, so that a screwdriver can be used to just screw and unscrew the bolts. I found a tube of weather stripping that I think will work well to fill the cracks from the inside. I also found a old PSU from a Dell laptop that outputs 18.67V at a max of 3.8 amps, lots of power in a small package and its all I've got around that is suitable for the job, but the circuit is rated for only 18V. Should I chance using it the way it is or should I try to find a 18V regulator and build a regulating circuit? One more thing I forgot to mention, if I touch the pots I get this extremely loud spanish AM radio station overlayed with opera music coming thoguh the speakers, only slightly quieter than my actual music. Its intensely annoying and I need to figure out how to get rid of it.
@ the spanish music There's gotta be a ton of jokes about boom boxes, the bronx, esses, etc You should be able to get rid of it by earthing the pots. Attach an eye connector or just tin a ring of wire around the thread of the pot, and tighten the nut on the wire, and attach the earth leads to the central earth point of the corresponding amp. Check the datasheet for the chips in your amps. If any of the chips have a maximum rating of 18v, then you'd want to be at least a couple of volts under that, but chances are the amp is just designed for 18v, in which case the maximum input would probably be in the 20's or even 30v. I'm just guessing however, the only way to know for sure is to check the datasheets. If you are gonna be taking it apart that much, then permanently attaching nuts sounds good. If you've got a welder, then perfect, if not, then probably vist an engineering/machine shop. You could jbweld or glue, but i dunno how many times that will last?
You could just use a diode to drop the voltage down to 18V. A Silicon diode droops .65V acording to Wikipedia.
The datasheet for the TDA2003 10W audio amplifier IC says that it can withstand 40V for 50ms peak, no word on how much it can withstand for a sustained period of time. @ r4ch3t [QUOTE = Wikipedia]However, if the polarity of the external voltage opposes the built-in potential, recombination can once again proceed, resulting in substantial electric current through the p-n junction. For silicon diodes, the built-in potential is approximately 0.6 V. Thus, if an external current is passed through the diode, about 0.6 V will be developed across the diode such that the P-doped region is positive with respect to the N-doped region and the diode is said to be "turned on" as it has a forward bias.[/QUOTE] If thats the part you're talking about from the Diode page, I think that means that the diode requires at least 0.6V for the P-doped region to become positive enough for electron flow to occur, thus the diode wont pass current until the circuit has at least 0.6V of power running through it. I don't think they reduce voltage like that.
They do need 0.6V to turn on, but once they are on they need that 0.6V to stay on, as such removing it from the circuit. You can try it using a 9V battery, a diode and a resistor, then check the voltage across the resistor, it will be ~0.6 less than the supply voltage. EDIT: It's just like LEDs, you have to calculate the resistor based on supply voltage minus the LED voltage and LED current. You would most likely be using a power diode as you are using several amps so a the voltage drop may be higher.
I've never actually used diodes (other than LEDs obviously) so what should I buy when I go to the electronics store tomorrow? EDIT I went downstairs and found a monster diode from a microwave, putting it on the PSU takes it from 18.6 to 14.2V! Big drop, but will work fine as I've been running the unit on 12V and its got tons of volume, so 14V won't be a problem. I also sealed the speaker compartment cracks by running finger covered in wood glue around the inside seams, hopefully the glue stays put and will seal the cabinet without holding it together very strong. I also cut the back into three segments, and the outer two that will be the backs of the speakers will be glued on later tonight once I stuff in the foam. EDIT 2 After cutting off the connectors that were on the diode, it now only drops to about 15.9V
I tested the new power arrangement for about a minute at medium volume, and afterwards the diode was very hot, too hot to touch. Should I think about a heatsink for it? Its only plastic. I'm not sure if it is meant for the amperage, as it was originally attached to a 2000V cap that was inside a microwave, but since it was 2000V I doubt if there was much more than 100mA on it. I think I'll still buy a diode as I really don't trust this one anymore.
I would get a new one to be sure anyway, since it is dropping 4V at 4 amps I think you said it is dissipating 16W which is quite a lot. Some diodes let you attach a heat sink to them. One of these should work well, it can handle 6 amps so that gives you some headroom.
Yes, I'll definitely pick up a couple tomorrow at the store. I'm not so happy with the sound this thing is producing. The tweeters seem to be overpowering the mids when you sit in front of it. From the side you get a better mix of sound but all the bass seems to be lost. I haven't tested with the backs on though, I'll give that a try in a bit. If theres a serious problem I might need to engineer a reflex tube into the bottom of the case to help out. My Tivoli table radio uses a single 3 inch speaker and a reflex system and it has better bass than this thing. EDIT Sound is excellent with the backs on, but to play well at low volumes (personal listening) I need to turn the source way down, I had my PC at 7% volume, and then turn up the amp. Having the PC at 100% causes crackling in the tweeters and other distortion. Not a problem though, it will take a while for me to figure out all the finer points of this thing. I'm thinking about adding one of these though: http://sayalhobbies.com/CatalogDetail.asp?link=148533 It would give me the control I want over different frequency ranges. I'm thinking about it and may add it down the road.
No need for diodes on the input, that chip is rated to take up to a constant 28v It sounds like it's all working well, but where's the update pics Did you drill the ventilation holes behind the amp section? Don't forget that the walls of that section would need to be sealed to the rear panel, so that the bass will not be reduced, but if the amp section walls aren't sealed, then the ventilation holes would be venting the speakers aswell, reducing bass.
Awesome, good thing I checked this right before going to the store! Ill post pics later today. The sealing didn't work as well as I had hoped, so even though its glued shut now I'm going to put some bondo in the cracks and sand it smooth. Even though its not 100% airtight right now it still sounds great, the level of bass is a good mix with the treble. Sealing it up more should make it perfect. I broke one of the damn pots while trying to test fit some knobs. half the stupid end of it snapped off, so I need to see if I can find some heartier 20k pots down at the store. This should be good anyway as the shafts on these ones are way too short and I can't get the knobs on. I also want to find some low-profile handles that I can put on the front to protect from falls, and I also need to work out my speaker mesh situation. As much as I like being able to see the speaker cones, I don't want someones foot going through them. And I need to find a handle strap.
Look here for homebuilt boombox, designed to run from 12v battery with a solar cell to aid recharge. This project is larger scale than yours, but same idea. http://www.diyaudio.com/forums/showthread.php?threadid=104402 Quote: "The cabinet is built as two separate bass reflex cabinet with a battery and electronics compartment in the middle. The holes on the front are cooling and cable access, while the handles on the sides double as reflex ports. It's designed to be used outdoors, so I chose a Qbox of 1.1 tuned at 82 Hz (my little nod towards 41Hz.com ). Trying to go belong 100 Hz in free-field is nonsense if you keep the other design parameters in mind. It's better to have a good middle bass performance to compensate for the lack of real sub-bass. It's loud! The sensivity is about 98 db/watt because of the double woofers and the magnet to magnet construction. With the amp giving about 50 Watts total peak power output, it should be around 113db total in peaks. "
Awesome Link! Would love to see some progress pics I'm getting started on mine as soon as my AMP6 BASIC kit arrives from 41hz!
Recent work: The back The laptop adapter The front The power switch and knobs Speaker grills I found at the store "speaker corners" that I found there as well Zennage Works For posterity
This last week has been tiring, and I wasn't home all weekend so I didn't get any work done until tonight when I planed and sanded all the edges. Now the corner pieces fit properly, and the fabric won't tear if it gets hit on an edge. Ill make a trip to Fabricland sometime this week and see what they have for thick fabric. I also still need to install the RCA input jacks on the front somewhere.
I'm nearing completion now in these last two weeks of summer. All that is left is to upholster the inside of the box and line some of the sides with foam, and figure out my plexiglass door that will go over it. Still not sure how I'm going to do that one. My camera was stolen by my family so they could take pictures on vacation, so here are some cellphone pics that I tried to fix up with photobuckets little web tools. and quick and dirty flashlight illumination Thoughts?
Looks cool, and it will look nice with the zen in there, which i assume you'll be installing with a frame or something to fill the gap. What's the plexiglass cover for? If you want transportation protection, maybe just find or make/mod a suitable bag for it.
