[xmokshax]

this isn't strictly HEAD-fi, but i'm wondering if anyone can recommend a DIY power amp that's suitable for use with a subwoofer (actually, it will be used with an enclosure that contains TWO 12" woofers, 4R impedance). i realize this is quite a tough load to drive well, but if anyone's dealt with an amp that might be appropriate, let me know. thanks!

 

[Joshatdot]

I too am looking for some amp for a box I am designing for my Kicker CVR 12"

 

[amb]

A class D amp would be a very good application for subwoofers -- it avoids large transformers and heatsinks, and be relatively easy on the wallet.

 

[error401]

The 41hz AMP2 or Truepath would probably be a good choice. You'll need to add a hefty power supply, but either of these can deliver 2x300W into 4R.

 

[xmokshax]

thanks for the replies. i'd been thinking that perhaps one of the 41hz amps would be a good fit. i have one of their amp10 kits sitting around waiting to be built, so maybe i'll give one of the more powerful ones a go once i finish the amp10. class D and class "T" (this is what Tripath calls its amplifier chips) are different names for the same high-efficiency switching amplifier technology, right?

the problem i'm running into is that transformers capable of delivering the recommended voltage and VA (~32VAC and >= 800VA) are dauntingly large and expensive. is there any particularly good source for nice, inexpensive transformers? i bought one for the amp10 from www.toroid-transformer.com, which seems to be pretty reasonably priced, but even their toroids at the above ratings clock in in excess of $100 for an amp this big. i suppose that's just going to come with the territory of building a high-powered amp.

 

[error401]

Yup, high-power transformers are big and expensive, there's no way to get around it (aside from use an SMPS). They seem to be $84 at Antek, which really isn't bad considering the size. I don't think you'll find anything cheaper elsewhere. Remember that unlike every other transformer manufacturer, they rate their trafos for voltage unloaded, so you probably want the next one up. Their datasheets contain the full-load voltage. Parts-Express sells Avel trafos, at around $90 for the 800VA size, and they might be a bit nicer than Antek.

Don't forget you'll need some C and L too and a hefty bridge rectifier to complete your PSU. Big caps aren't cheap either. You're looking at about $12 per 15,000uF at 63V, and you'll want at least 30,000uF per rail for this amp, maybe more. With the other PSU components (line filter, a couple chokes, additional caps, rectifier) you're probably looking at at least $75 on the PSU above and beyond the transformer. Add the amp kit, connectors and a case & heatsink and you're in the $500 range for this build.

Class T is basically the same as Class D. If I remember correctly, the difference is that Class T amps change the modulation frequency as well as duty cycle during operation, or at least something along those lines. It's still a digital amp operating with a modulated square wave.

 

[amb]

I don't see any reason not to use a switching supply for a subwoofer amp. The crossover, and the response of the woofer will effectively filter out any RF noise. The only drawback is that there aren't many appropriate off-the-shelf switchers and building one from scratch is much more complicated than a big transformer, rectifiers and a couple of caps.

 

[tjohnusa]

Quote:

Originally Posted by amb /img/forum/go_quote.gif A class D amp would be a very good application for subwoofers -- it avoids large transformers and heatsinks, and be relatively easy on the wallet.

That would drive it no doubt, but we are talking transient power that may require 4 or 5 times rated rms to be accurate. The reason for the big xformer and caps is to supply that power when needed. That is why the new audio equipment out is not as good as the stuff from the 70's. When listening to a typical 10 watt volume you can hit some bass peaks that need 50 or 60 watts to reproduce accuratly. And by the way 10watts is quite loud with efficient speakers.

 

[amb]

There are class D amps with output power in the hundreds of watts range, even 1000 watt... for example those based on the B&O ICEpower modules (linky: 1 2 3). I think that'd be quite sufficient for any domestic subwoofer application!

 

[steinba]

But you can't buy ICEPower modules for DYI-ing, can you? (Well, maybe you can.) I tried to, but was told I needed to be a commercial company developing/selling amps to be allowed buying 'em.

Are there any more DIY frendly alternatives? Is that what 47Hz and Truepath is?

 

[digitalmind]

Quote:

Originally Posted by xmokshax /img/forum/go_quote.gif this isn't strictly HEAD-fi, but i'm wondering if anyone can recommend a DIY power amp that's suitable for use with a subwoofer (actually, it will be used with an enclosure that contains TWO 12" woofers, 4R impedance). i realize this is quite a tough load to drive well, but if anyone's dealt with an amp that might be appropriate, let me know. thanks!

Two 4 ohm woofers or two 8 ohm woofers making a total of 4 ohm? Driving a pair of 4 ohm speakers in parallel is going to wreak havoc on the amp, and thus on your wallet.

Interesting thread, lots of good recommendations. What kind of drivers will you be using, and at what frequencies?

 

[Ferrari]

Agreed with what amb said, class D amp is indeed a very good for sub-woofers applications.
I have used a Hypex DS4.0 class D amp module in a sub-woofer in the past with great result (400W/4Ohm with on-board LP-filter/switches, Hypex is a Dutch manufacturer).

 

[amb]

Yes, it's true that ICEpower modules do not seem to be readily available to DIYers. I mentioned them merely to make a point that there are very high power class D amps out there. An alternative are the Hypex UCD amp models, available from DIYCable.com as complete amps or as assembled boards and parts. The UCD-180HG, UCD-400HG and UCD-700AD output 180W, 400W and 700W into 4 ohms, respectively. They also offer matching power supplies and other parts. See their Hypex amp parts page. Considering the prodigious output, the prices are remarkably reasonable.

No affiliations, just passing some info along.

 

[steinba]

Quote:

Originally Posted by amb /img/forum/go_quote.gif See their Hypex amp parts page.

Thanks! I've already found the Truepath kit on /www.41hz.com, though, and am jonesing badly.

I see that he's based in Stockholm, and that makes support and adaption to the (equivalent to the Swedish) Norwegian power grid so much easier.

I need a new power amp. ...And suddenly I realized that I'll need a new preamp (line selector and attenuator) as well. I can smell warm ABS plastic from the VISA card already-

 

[audiop]

Hi,

I have made many Truepaths and I like these amps so much that I have made a website dedicated to them

. It includes detailed instructions on building and testing and products related to Truepath. Please take a look, and if you want to know more, please PM or email me!

Rgds.

Audiophool@maedos.com