#1
First and foremost I know and don't particularly care that if at all possible then it will sound absolutely horrendous.

That said, I have an old subwoofer with a speaker and was wondering if there was any way I could turn it into an amp for my guitar. (Actually it could be cool if I get could get rid of the speaker and just have it amplify the signal for it to then go elsewhere)
#2
Your question is such an amazing coincidence, perhaps we are cosmically linked or something else weird that I also don't believe in. Anyways, cosmic stuff aside, I JUST did that on Thursday, and I was going to post pictures, but I only have the first few cuz the camera battery died. I was thinking I would open it up again (to re-install the heat sink which I ignored for my preliminary testing) and take some more pix. I hope to do that still.

Before starting, I just plugged in using a 1/4 to 1/8 adapter. It seemed OK, but much quieter than I had hoped.
Step one: wire a 1/4 jack to reduce the wobble noises. That was done by poking around with a meter and picking spots to solder my wires. I left the original 1/8 jack in place.
Step 2 was to find the pinouts of the amp chip and jack in a volume pot. Success was obtained, but it turns nearly out pointless. The original wiring was full on, so nothing gained Hey, that's a pun.

You should do the project too. It is likely to be a waste of time, from a practical point of view, but fun and educational. And perhaps your particular subwoofer has features that make it more useful than mine.
#3
should be do-able but you'll have to graft an amplicgication section out of something or build one. Don't know if it will suond nice either since it's a sufwoofer speaker and hence made for low frequencies
Gear:
Marshall haze40
Yamaha GA15
Line 6 pod GX
Ibanez PGM301
Yamaha self customized EG012
Jackson KVX10
Boss DS1
GE 7
BD2
CS3
Vox satchurator
Home made TS808
Belcat delay
#4
Here's some pictures, some are not very well lit and/or out of focus, and repetitive; but its free, so I just put them all out there. http://s1182.photobucket.com/albums/x443/jamescollie/sub%20woofer%20amp%20hack/

I did the jack part myself, then my buddy Lou came over and helped me interpret the circuit.

The input signals get split crudely through capacitors and go to two separate amplifiers, one for the sub speaker, and the other for the 'regular' line out. The line out stays stereo, but the signals to the sub are merged into mono. This is the only part we played with, so I assume the regular output of the unit still functions as before. Theoretically, the sub section should be filtering out highs, but I can play right to the top of the guitar range and get sound with only the sub speaker, so the 'filter' is ineffective.

Our goal for the evening was to increase the volume. After removing the heat sink we got a number off the amp chip, CD2025CP, and googled it. We found this pdf, http://www.datasheetarchive.com/dl/Datasheets-115/DSAP00572.pdf
which really seemed to match what we thought we were looking at, but its in Chineese, so it didnt really help us. We did learn that it was a 2.3 Watt amp, and that helped us find this version http://www.datasheetcatalog.org/datasheet/SamsungElectronic/mXruxwu.pdf which we concluded is the original chip that the 2025 was copying.

Using the first application note, on page 3, we decided we can easily add a volume control on pin 9. Pin 9 is grounded through a cap, so we removed the cap for easy access, replacing it with a pair of wires that we ran to our pot, and re-attached the original cap to the pot because it was way easier than soldering to the board.
#5
I have done that sort of thing with car stereo amps so I can play off a car battery. I just needed a pedal in front of the amp to boost the gain going into the amp,you need some sort of pre amp or it will sound like crap. And a full frequincy/music speaker.
What the hell!!!
#6
I've got to check still exactly everything at my disposal. The subwoofer thing basically I took out completely and this is what I found:

A very small board that says "SD05/920F I/O" and about which I cannot find any real information (not particularly hard to figure out though) and attached to it is a 3.5mm in and two female rca outs (which were originally linked to "In-put" and "out-put" connectors on the same board.

There's also space on the board (with nothing on it) for a L-Out and a rather large "J20" (don't really know what it is but judging from the form factor of current components I guess that's where a 3.5" out would go if I were to add one.

And there was another board labeled SANRUPID SR920A and some numbers which I presume to be a date. I haven't been able to find much info on this either but from what I can figure out, connected to this board were a couple of power cords (there's an AC +-13.5V and an AC +9V.

There's also a section labeled "Sub Out" and on it is a couple of wires soldered directly to the subwoofer speaker.

Other than that the board has a heat sink, a shitload of capacitors and resistors and "BASS" and "VOLUME" knobs as well as a "3D" sound button.

It just occurred to me I also have recently disassembled a non-working Logitech iPod docking station which I could also use for parts. The speakers on that were pretty decent but I've not really looked at the boards at all.
#8
Where would I get a 386 chip? Please keep in mind we don't have Radioshack here (they went bankrupt, somehow...) so while I can get electronic components I don't have a very good supply and getting them will usually mean a long trip.
#10
Also, would prefer (if possible) to make something to plug on the AC. I will post more details about what I currently have later. From what I've seen on the subwoofer board (the logitech one is not entirely mine so I haven't disassembled it further) I've got a JRC 4558D chip and a TDA2030A which is coupled to the heatsink.
#11
Quote by Lord Kamina
Also, would prefer (if possible) to make something to plug on the AC. I will post more details about what I currently have later. From what I've seen on the subwoofer board (the logitech one is not entirely mine so I haven't disassembled it further) I've got a JRC 4558D chip and a TDA2030A which is coupled to the heatsink.

I spent about 3 minutes googling and those look like really useful parts!
#12
Quote by RebuildIt
I spent about 3 minutes googling and those look like really useful parts!


More or less the same I did, which is why I posted about them. I'll take a trip down to my electronics shop later in the week or next week and see what else I can get (I need to buy some basic stuff like a solder removal tool also)

If you know other parts or chips that could be useful please mention them so I can see what they've got.

The other thing, I pretty much understand the theory behind circuits but am an absolute newbie to making or modifying PCB boards, I'd be extremely grateful if somebody could provide me with a tutorial!

EDIT: The board also has two B50K potentiometers (volume and bass)

From what I understand, the transformer was connected to the larger board on a 9V AC point and a 13.5V AC point; a smaller board loaded just with input and output jacks and 3-pin "in" and "out" connectors. From what I can see, the TDA2030A was connected directly on the output pin to the subwoofer speaker. The board also has a 3-pin connector right between the two B50K which I assume would be connected to the "out" on the other board and a 3-pin cable at the center which I assume would be connected to the "in" in the other board. Does this make any sense or did I probably confuse the in and out?
Last edited by Lord Kamina at Jan 18, 2012,