I want to DIY 50W subwoofer amp, someone tell me what to do.

[johnnyrichards]

The HTiB upgrade subwoofer I built last fall is in need of amplification. Here is what I want:

1. Internally mounted, so no heat sinks. The subwoofer is vented, so at least some heat build up can be avoided.

2. 4 Ohm stable.

3. I am willing to hack up the back of the enclosure for power and signal connections.

4. Cheaper than buying the 50W plate amp at MCM for $60

5. 50 watt output.

6. Crossover optional. If I decide to cross it electronically, I am very open to a DIY electronic crossover add-on.

So tell me what to do, I don't know enough to even begin researching this topic. I browse through almost every DIY amp topic on this site, and am at a complete loss.

It is for this guy here:

[Deward Hastings]

I was going to say "No way, Jose" . . . 'cause any analog amp will require an external heat sink, and even the cheapest Sure Class D boards (of sufficient power) plus power supply total over $60. But just out of curiosity I went looking anyway, and . . .

http://www.parts-express.com/pe/show...number=269-176

Certainly cheap enough to try, and 12V at 4-5 amp is easy to come by even in wall warts. Worth a try . . .

[jonpike]

Hmmm... tough job, to meet all that, especially #4. It's very hard to get even near $1 per watt for a full amp and power supply.

You could do an analog amp of some kind, though at the 50W level, you might have 50 or more watts of heat to get rid of, just too much for a closed system without external heatsink or plate of some kind. A vented sub is still pretty much a closed box, from a heat exchanging ventilation point of view, I'd say. A 3886 chip amp, mono channel, designed for 4 ohm would do, and the amp part would be cheap, but the power supply would push it over the limit, the Avel Lindberg 160VA (admittedly a bit large for a single channel) 18V +18V transformer is nearly $50.

Switching amps (D, T, H, whatever) will have much less waste heat to get rid of, being 70-95% efficient. You very likely could get a 50W amp in the box with no external heat sink, and not get too warm. I haven't refreshed my memory on what those Sure amps cost in that wattage range. You'll need a reasonable sized power supply for them, and then again, total cost might break your budget.

I don't mean to be a damper, but unless you feel like relaxing the budget requirement, your best bet is probably the plate amp.

Now, even going that way, I could help you with DIY crossover instructions... even with the plate amp crossover, you might want to add a high pass for the mains, or go to a custom highpass/lowpass for better integration with your mains, etc...

Hope that helps...

[jonpike]

Heh... that's what I get for starting my response and walking away for a bit. Deward showed up, wrote and left...

He''s found you something real cheap.. (hopefully not in the negative sense)
I wonder what you really get at 4 ohms load. "100W" at 1 ohm might imply 25W by the time you get to 4 ohm, but hey, can't beat that price with a stick. Still need some power supply, but if you've got an old PC power supply or something, its so cheap its worth a shot. Depending on your listening level, it might turn out to be enough power even if under your 50W target.

You'll probably still need to mount the amp out on the back of the box...

[philiparcario]

http://cgi.ebay.com/MEAN-WELL-SPU50-...#ht_4690wt_835


this is a good quality power supply. I purchased a few the seller will go lower maybe 15 if I remember. if you open it there is a small pot that allows voltage to go from 11v to 14v. they are clean sounding no hash from the switching parts.

[1100xxben]

I was going to say "No way, Jose" . . . 'cause any analog amp will require an external heat sink, and even the cheapest Sure Class D boards (of sufficient power) plus power supply total over $60. But just out of curiosity I went looking anyway, and . . .

http://www.parts-express.com/pe/show...number=269-176

Certainly cheap enough to try, and 12V at 4-5 amp is easy to come by even in wall warts. Worth a try . . .

That amp has been discussed before, and I think at 4 ohm you'd be lucky to get anything more than 15W of CLEAN power out of that amp. If you're happy with that though, it is a very inexpensive option.

Edit: I forgot to mention that you'll most likely need a 14V (or slightly more) supply to get that power out.

[neildavis]

The HTiB upgrade subwoofer I built last fall is in need of amplification. Here is what I want:

1. Internally mounted, so no heat sinks. The subwoofer is vented, so at least some heat build up can be avoided.

2. 4 Ohm stable.

3. I am willing to hack up the back of the enclosure for power and signal connections.

4. Cheaper than buying the 50W plate amp at MCM for $60

5. 50 watt output.

6. Crossover optional. If I decide to cross it electronically, I am very open to a DIY electronic crossover add-on.

So tell me what to do, I don't know enough to even begin researching this topic. I browse through almost every DIY amp topic on this site, and am at a complete loss.

It is for this guy here:

DIY to me involves ordering boards and parts and board assembly

The amp in the picture is a stereo amp, with two 50W channels. It uses the DDX "damped ternary" modulation, which is more efficient than the Tripath modulator in the Sure boards, so less heat. Also, the modulator has a lot of digital "smarts", including shut-down with no signal input. The auto-shutdown helps reduce heat. There are also 4+ digital biquads per channel, which can be used to implement a crossover and EQ (8-pole LR crossover, if you want...).

The amp requires a 24v supply. This particular board just has SPDIF audio input, but I've got other versions laid out that have analog input and USB audio.

PCD layouts, schematics, and other details available...just ask.

[Jmillerdoc]

Maybe you could work some sort of magic from one or two of these?
http://www.parts-express.com/pe/show...=Bazaarvoiceps

[LouC]

The HTiB upgrade subwoofer I built last fall is in need of amplification. ...

Johnny,

I bought some small (like 6" square) MCM plate amps awhile back at $50/pair they are rated at 45 watts/channel. Email me if you are interested. I've got far too much cr@p...

[johnnyrichards]

I have the 70 watt PE amp hooked up to them right now. This amp is physically too large for the enclosure.

This little guy sounds much better than it should. It doesn't dig ultra deep (anechoic to high 30's, but I have it corner loaded right now and it is excellent for music, including some techno and rap I threw at it.

These little TB drivers are exceptional for what they are, and I really wish PE would carry them again.

I think I have a line on the perfect plate amp for it, and I thank you all for your help and advice. It appears basic DIY amps are not competitive with off-the-shelf just yet. Neil's solution intrigues me, though.