Axiom Home Page Forums General Discussion The Water Cooler Gonna Try Building a 1kW Class D Amp for Only $396

Just put the order in for some parts to try building my own Class D Two Channel Amplifier. Saw this thread and it really intrigued me:

http://www.audiocircle.com/index.php?topic=76400.0

(For anyone even remotely interested in DIY type stuff, it's a fascinating thread)

After contacting the owner of the company who makes the amp boards(Tom, who seems like a really nice guy), I ordered a large toroidal transformer (1000VA), heavy duty power supply, and two amplifier modules which should output 500W each easily when bridged. Since they are Class D, they are much more efficient (>90% vs 50-60% for class A/B) and should put out much less heat. THD numbers look really good too. I should be getting the parts by this weekend and will do a quick assembly first to test things out and see how it sounds. I'll let you guys know how it goes.

Steve, did you check out the Sure Electronic DIY amp boards at Parts Express by any chance? not sure if it's comparable at all to what you're looking at.

Yep, they're in my bookmarks (as well as some others). Sure Electronics output power was much lower, and the THD+N at rated power was REALLY high (10%). THD+N at rated power for the modules I bought is <1%.

do they furnish the instructions? Also, what about the case? Can you provide links?

I'll be VERY interested to find out how this goes!

They supply individual parts and kits. Instructions are supplied too (also on their website):

http://classdaudio.com/index.php/

You're basically on your own for the case, but just about any enclosure would work. For now, I'm just going to assemble it on a block of wood. If it sounds great (like most have said), I'll probably build a nice wood enclosure.

Tom also buys in bulk and will pass the savings on to you. The 1000VA toroidal transformer would go for $100 alone unshipped if I tried to buy it myself (sucker weighs in at 18 lbs alone).

Read through the thread link I posted above if you get a chance. There are some wonderful examples of systems put together, as well as some nice DIY cases. I'm pretty excited about this...

Please update us with a photo or two of your build and your thoughts after completing it and taking for a test drive.

Looks good, Steve! I'm excited for you. Let us know how the build goes!

Very cool. I may have to look into this when I need more channels. Good luck!

That Class D Audio kit gets my thumbs up too.

Make sure to post your progress on the build, Steve.

Gets your thumbs up… where?

Will do. It's shipping today so I should have the parts by Friday. The first assembly will be quick and dirty just to get it going and test it out (it will be ugly to look at). It should not take more than a couple of hours to do this, so I should have my initial impressions this weekend (I wish I had a THD analyzer!). I think I may wind up buying a clamp on ammeter to measure amp current draw and use my sound meter to measure db output. I know this amp will use less power to get the same db output, but I would love to take some measurements against my AVR-3806. I do have an infrared thermometer, so I'll shoot the heatsink to see how hot it gets (open air).

The final assembly (time and money involved) will depend on how good it sounds

Geektastic.

I'm interested in this. But I'm not really very good at soldering. Many posts in the linked thread go far beyond my current or desired level of electrical theory.

Pictures would be cool.

Thanks, Steve!

I've only done 2 builds. Back when I was an early teen. I bought 2 of those light kits that made lights flash in time with the music. The instructions were a little fuzzy concerning the orientation of the rectifier. I put it in the way it looked good to me, but when I first went to turn it on, it blew up in a pile of smoke. The second one, I turned it around and it worked just fine.

One of the pluses the lured me to this system was that you really do not need to solder anything for the initial quick and dirty hookup. All of the connections between the boards are done with screw terminals. Soldering is an option of couse down the road for external run and trip leds, power switches, and binding posts.

The other thing that lured me was all of the positive comments, and the quality of the parts involved. The Heavy Duty Power Supply uses Nichicon 100V, 105C, 4700uF capacitors (very good quality Japanese capacitors). I priced them out online and the best price I could find was about $14 a pop when buying less than 50 of them at a time... The power supply board has 6 of them, and he sells the whole board for $65 before an additional discount if you buy a kit.

Wait, can you use them bridged with your M80s? I didn't think you could bridge amps when you were dealing with a 4 ohm load.

These amps are rated down to 2 ohm individually, and will work bridged with a 4 ohm load. I also confirmed this with Tom before I bought them.

Sweet. Which model of amp is it?

CDA-254. The 4 suffix designates 4 ohm stable. Although he only publishes it as 500W 8 ohm bridged, he does confirm it will also drive 4 ohm when bridged. Power will be slightly more, but not double. It will start clipping (>1% distotion) long before 1000W.

Oh neat, I didn't realize he included standoffs and mounting screws.

It is quite the kit, he may have a bunch of sales on his hands if this build works as well as advertised

It would be really cool if he offered a pre-drilled chassis and parts for the pretties.

I think I might love this company. I was looking at the user manual, and noticed a VERY interesting rendition of the flag printed on the amp board...



So, Steve, a couple questions, if I may.

1. What's the functional difference between buying two of the CDA-245S kits and one of the CDA-2000 kits? They seem to be the same amp boards. Do you expect more power by using two (smaller?) power supplies and two (smaller?) toroids?

2. If you're using two of the CDA-245 in bridged mode, you're basically building two monobocks, right? I know it's a minor detail, but I don't see how you wire the external LED's in bridged mode.

Seems like Steve bought a custom version of the CDA-2000 kit--with the large PS, the 2 CDA-254 boards, and a 1kVA transformer (larger than anything in a kit that I see).

I think that sums it up.

1) The 254S kit has a low profile power supply (smaller caps). I went with the heavy duty power supply. The power supply board will power both amps, and each amp will be bridged. The CDA-254 amp board actually has 2 amps on it, and I'm ordering 2 CDA-254 amps, and will bridge each one.

2) Yes. 2 monoblocks in 1 case with a shared 1000VA toroid. As far as the led's go, I think you just wire the left channel since that is the channel you will use when bridged. Not sure though.

Easy enough to find out on number 2, just look at which LEDs on the board light up, right?

Ah ha! I was apparently not reading carefully enough. Thank you very much for the clarification, Steve.

How come the CDA instead of the SDA or TI amps?

The SDS was about $100 an amp more for things I did not need (balanced inputs, input level adjustment, etc.) The TI amps have greater distortion (their full power rating is actually at 10% distortion, vs. <1%), and were not as well received by the group. In reality, a lot of people preferred the sound of the SDS amp compared to the CDA amp, but most said it was not a difference that was worth the prices. Some people said it had "a deeper soundstage" and "presence". I tend to ignore comments by people who make those statements about amps.

The other thing that's kind of cool about the amp modules is the ease in switching form bridged to stereo mode. If it turns out that the M80 impedance is too low (it does seem to dip to 3 ohm) and the amp starts to overheat or cut out, I can always unbridge the amps by just changing a jumper and wiring the output from +V/+V on each amp, to +V/-V on each channel of the amp. I'd still have tons of power at 250W per channel, and now have 4 channels so I can also power the VP180 with it (and have 1 channel left over). It's a fallback position just in case.

HA! Now that's a random place to have such a sticker.

Good luck with everything Steve, this is really cool!

That amp is certainly impressive. I've always wanted to do a DIY tube amp or DAC. However, this should be a perfect pairing for the M80's, you'll really be able to rock the house!

As always, remember that we love pictures

how much soldering, etc. is involved, or is it just plug it all togethor?

From what I can tell, if you want to make it pretty, you have to solder. If you just want to try it out, you can just screw the wires into the posts.

Exactly what I was wondering. My guess is you do ALL the build/soldering although the website infers that most of it's pre-built. What's the scoop, Steve?

Apparently you just wire it together. Source

Since this amp seems very simple to put together, if you really wanted to go DIY you could do component upgrades. Most of the time they are transformer or capacitor upgrades. Some believe that component upgrades can push "cheap" equipment with good circuitry designs into something that's great. Tried looking up mods for this amp, couldn't find much.

Class D amps don't take to tinkering with their designs too well. You really need to know what you're doing before you substitute any component. Else you end up building yourself a 1000 Watt AM radio station.

Sorry guys, I was out of town on business... Just got back and the box from ClassD was waiting for me! Quick shipping indeed! The toroidal transformer is coming directly from the manufacturer, so I hope it comes soon. I'll start mounting and wiring what I have so far tonight. Here's a couple of pix:

PS - The ruler is there for TomTuttle... Sense of scale.

NICE, So.....is it done yet?

Chris is right, you have to be careful with Class D type amps. Tom will upgrade the boards to whatever caps you want. You can either have him buy them, or mail the caps, etc. to him. He'll do the soldering for you. I asked Tom about an upgrade of the power supply caps from 4700uF caps to 10000uF caps. He said each one would cost about $15 more because he does not buy them in bulk. He said he would not recommend spending money on that though because it was just not worth it (I would not really hear any difference). I trusted his opinion and went with the stock caps. He did say that the toroid upgrade was a wise choice for multiple amps.

I can tell you from looking at what is on the board, these are high quality components.

Took about 2 hours, and it isn't the prettiest thing now, but I have it all wired now except for the toroid. Hoping it will come tomorrow of Saturday. I used 12 gauge wire to connect the power supply to the amps, and it was a tight fit (it's where I spent most of the time). I'll probably go with 14 gauge in the permanant installation.

Very cool Steve! I have always wondered about DIY amps.

Kewwl! thanks for posting pictures, Steve. It looks like something I might want to try as well.

This isn't looking too bad. I was originally thinking you had to solder all of the pieces onto the boards. I may have to give something like this a try.

yeah, if I'm not mistaken they are in some type of screw or tensioned socket? Just when you get this thing all juiced up and the capacitors are full, don't touch anyting.

Nice! Where'd you get the RCA connectors?

Yes, the caps are my main worry Randy. I'll probably have to let it sit for a long while unplugged to let the caps discharge before I'm ready to take it apart for the final build.

The sockets are all screw down. Real easy.

Once the toroid arrives, my plan is to test it out first using my iPhone as the input, and my old VP150 as the sacrifical lamb before I even think about hooking it into my system. I'll test one channel at a time with the 6 ohm load of the VP150 and make sure everything looks good. If it all checks out, I'll hook it into my main system and have it drive both M80s using the AVR-3806 pre-outs.

I just cut apart an old cable I had lying around for now. I'll buy RCA connectors with solder tabs when I'm ready for the permanent installation.

That's what I figured, but I was thinking the wires inside must have been TEENY.

The + wire certainly was.

Also, for the people who are interested, I noticed that the amp boards that I received did not have the Maron 560uF caps as shown on the picture on the ClassD site. A lot of people on the audiocircle board had commented on the lower quality of these caps in respect to the rest of the amp. Tom must have listened because they are now Panasonic 680uF caps. So again, I see a lot of high quality parts on these boards.

I just read through the manually and see how they are setup if you want to build external off/on switch as well as extending the leds. A little soldering possibly, but nothing to crazy. Man if this works out Steve and your happy with the performance and sound of D technology, I may have to consider this some day. Thanks for bringing this to our attention. Sure beats the heck out of the cost of other mfg'd amps with the same power. Are you going to build a mono version for the VP180 if all works out?

I'm hoping it sounds at least as good (but with more power) as the amp stage on the AVR-3806. I know, high hopes... But, if it works out that way I was considering a mono version for the VP180 in the short term, and in the long term buying exaclty what I bought again but wiring it unbridged to power the four surrond/rear channels. At that point, I would sell my AVR-3806 and buy a preamp/processor instead (something similar to the Emotiva UMC-1).

What, I'm the only one who needs scale?

Great, Steve. I appreciate the pictures and writeup.

Looking very good. As I mentioned if this works out, there will be a number of sales from this build. Now just to decide on a chassis to put this into. Anyone found anything online. I could build a wood enclosure like others have done but I would like the manufactured look(steel/plastic/aluminum) to match the rest of the system

A guy named Jason (jtwrace) on the audiocircle board makes a case for this with everything pre-drilled and labeled. His gallery is here:

http://www.audiocircle.com/index.php?action=gallery;sa=album;id=4288

I have not contacted him yet, so I don't know the cost or if they are still available. I'm not sure if I'm going to build a case myself or go with something like that. You can however find some places online that have plain old aluminum or steel cases if you choose to drill yourself:

http://www.par-metal.com/

I'm hoping that the amp sounds great and he does get a lot of business becuase he seems like a nice guy who makes a nice product (I always like to see good quality parts being used). I know on the audiocircle site he gave that group a 5% discount. So, if after I put it together and it sounds good, I'll let him know about this board and see if he wants to offer a board discount to us.

Here are a couple of sites for enclosures-- Hammond, and Mouser and Lansing.

Also, here's a place that can custom cut and punch a front panel.

This site looks interesting. You can fully design your own case and they can build it for you. I have no idea of the cost, but it looks pretty neat for those that don't have the means/knowledge for making his or her own.

Steve, that kit looks very cool. I'm eagerly awaiting your impressions. I like the fact that all the dirty work is kinda done already. I am certainly a novice when it comes to soldering and this seems like a good first project.

Steve which model did you get the 2000 kit?, man they have lots of kits and different model numbers, kinda confusing. I thought when bridged you could only drive 1 channel, or is that for each board you have?

See my post a few sections back. He essentially bought a modified 2000 kit.

Got a little antsy, so I dragged out my variable AC power supply and dialed it into about 50V AC to test the amps. I will say this... IT GETS LOUD! The sound seems about the same as the AVR-3806, but its hard to say because I'm just running one VP150 at a time. I hit 104db (@ 1m) constant output with the iPhone turned all the way up, and was pulling about 50W. Amp IC temp hovered around 56C (that's the actual chip, not the heatsink which was only warm to the touch). But just as I was typing this mail, the toroid arrived! Will be away for a bit doing some rewiring, but looking real good so far. Pix attached:

Test setup:


Temperature:


Toroid!

Thanks for those links everyone, the Protocase supplier looks like a winner if it isn't too expensive.

That torroid looks pretty tall 6-8", that would allow for alot of room for air circulation around the system.

The toroid is 6.2" diameter, and 3.5" tall.

Wow!, only 3.5 tall those pics do nothing for sense of scale. That makes it really nice for a lower profile cabinet, this just keeps getting better and better

Well, toroid all hooked up (was a bear, it has 2 primaries and 4 secondaries) and tested on the VP150. Everything working great! Going to put it to the real test now... A pair of 4ohm M80s.

That's almost too easy.

Almost? If the dude sold predrilled cabs, it would be a no brainer.

The M80s acutally got the amp heatsinks hot in bridged mode! I could sustain 102 db, both speakers, from 12 feet away no problem. The amp started going into protect mode (high heatsink temp over 100C) at about 105db sustained (my ears are ringing right now). What the amp does is turn off the affected channel until it cools and turns it back on again. I'm going to do a quick rewire to unbridge the amps to see how far I can push them. Some people had this problem and added to the heatsink and put a fan on it.

The sound is INCREDIBLE! It really does sound punchier than the AVR-3806. Very clear and tight. The wife said it was not even close (she liked it better than the AVR-3806), but it was a bit more close for me. Definitely punchier and tighter sound. If it sounds just as good unbridged with a higher output headroom before overtemp, I may leave it that way and hook the VP180 up now.

This dude does!

http://www.audiocircle.com/index.php?action=gallery;sa=album;id=4288

Does he still?

I like this thread!

Okay, I've tested the system out and listened for several hours. I also hooked up the VP180 once I unbridged the amps. Here are my opinions.

Sound Quality - At least as good as the AVR-3806, and I think a good bit better. My wife thinks it's much, much better. Sound seems tighter and less muffled. I don't know if it's a characteristic of the Class D type amplification, having separate amplification, or a little of both. We switched back and forth between the AVR-3806 and the ClassD amp several times, and every time it felt like cotton came out of our ears.

Power - Here's the rub. I cannot test the unit to full power, even in unbridged mode, because the amps will cut due to high temperature. The best I was able to sustain without any cutouts was a constant 102db in my listening position. When I looked at the wattmeter, I was pulling about 90W. That's with 3 channels going too. Interestingly, the VP180 always cuts before the M80s. Maybe something changed with the new crossovers and drivers. The website (and the people on the board) have said that higher power demands require an active cooling system. When I shot the heatsink, it was at 73C constant. So, I think adding fins on the heatsink and the addition of a fan would allow me to bump the power up.

Fun Factor and Ease of Build - It's REALLY easy to build and a lot of fun. I'm really proud of it even in it's unfinished state. Knowing I can go in and tweak things (like thinking of a way to provide a more robust cooling solution) is a lot of fun for me.

Recommendation - I would recommend these kits for people who normally listen to music below 100db. If you listen in the 85-90db range, there is no problem whatsoever, and you can go with a much smaller toroid and amp size (driving the cost down even more). The sound quality, at least to our ears, easily rivals or beats that of high end professional equipment. I would also recommend this kit for someone looking to amplify surround speakers on the cheap, or someone who likes to tinker around (especially coming up with a nice cooling solution).

I'm going to keep the amp hooked into my system. I like the change in sound that much. Plus, I usually listen in the 90-95db range, so I'm good with the volume. I just want to be able to figure out a good way to get the most I can out of the amp modules... But hey, that's part of the fun right?

Good for a Denon 9.2 that has pre-outs for 11.2 (or 9.3 to 11.3)

It's hard to judge from the pics. Is the heat sink taller than everything on the board? Can't tell if it clears the inductors or not.

I was thinking you could get a finely finned heat sink and use a thermally conductive epoxy to attach it to the existing sink. Something like: http://www.arcticsilver.com/arctic_silver_thermal_adhesive.htm

Funny you say that Chris. I'm going to Fry's tomorrow to pick these up:

http://www.frys.com/product/5591560?site=sr:SEARCH:MAIN_RSLT_PG

Turns out the are the exact width of the heatskink, and a set of 8 will cover the entire top. They are self adhering as well.

I also just ordered two 48VDC fans for $1.75 each. The output of the DC power supply is 50VDC.

Keep us posted Steve. Curious, if you plan to call the seller and discuss the shutting down issue, if they claim 4ohm compatible, and shutting down when it is not within a case, plenty of ventilation?

My Odyssey mono's I had got fairly hot to the touch and were a A A/B design, which is not as efficient as Class D. I'm just trying grasp the concept of having all that power if you can only listen to levels the Denon will easily put out. I know the sound appears to be better/tighter overall, but as John always says, why have all that extra umph if you don't use it.

I suppose for the small price you payed, it still was a good venture.

Well, given that he was bridging and pushing >105dB on 4 ohm speakers, I'm not surprised it shut down with those teeeeeny heatsinks.

So, so tempted to try this out. Don't need it... don't need it...

Keep telling yourself that Ken, let me know how it goes.

I have fabulous resistance to buying toys, mainly because I can never decide which toy to buy, and oh, it might go on sale, but now it's on sale, maybe I should, maybe I shouldn't, oh look, it's not on sale again...

But he said above even in unbridged mode it would still cut out because of overheating. I guess I'm just confused on if Class D is supposed to be 85-90+ efficient over A or A/B designs which are in the 50% or less range, no case for trapping the heat, and 4 ohm compatible, why the issues?

If there is a good sound improvement, for the price it still is a great dealeo.

Oh, I missed that bit.

Are the heatsinks those little strips of silver metal in the pictures, or were the real heatsinks removed for the pics ?

A class AB (typical amp) with that power rating would have heatsinks the size of your head (ie a lot more than 10x the size of the heatsinks in the pics) wouldn't it ?

Yup, the little strips are the heatsinks.

Yeah, I'd say at least the size of your head, if not two heads.

Looks like the design's been changed a bit on the shipping amps--I see in his pictures that it has RCA jacks (maybe?) on the boards, but yours has screw terminals in those locations.

How'd you wire up the plug to the outlet? That would probably be the thing that would make me the most nervous.

I am guessing moving up to the SDS line might be worth it as this series has a finned heatsink.