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PostPosted: 25 Sep 2008, 17:00 
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I'll second the AN-6218. Most seem to recommend a min of 300VA per module, so 600VA for two modules should be good.

As Ri noted, once rectified the DC will be about 1.41 time the AC. Also, from the datasheet, the transformer puts out about 18.7V into no load which is about 26.4V and still less than 27V, so that is good.

Note that the AN-6218 has dual secondaries. So what you will do is give each module its own secondary. That is better than using one large transformer with a single secondary.

Cheers

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PostPosted: 03 Oct 2008, 13:33 
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Joined: 26 Aug 2008, 20:57
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Location: Atlanta
I have an amp9 at the house and it is an awesome amp.

Keep in mind it is about 40wpc in reality since they like to rate at 10% THD...but it sounds incredible...way better than the TA2024 tripath chip, probably due to more headroom...better than the dual mono TK2050 I had too.

You can run it off a 12v power supply in a pinch but you have to be careful about output.

My buddy found an enormous 24v SMPS that retails for $850 for $50 on ebay...he didn't ask the guy where he got it but it probably wasn't a retail outlet!!

I like using SMPS on my tripaths for simplicity sake.

Here is a 6.5A SMPS from all for $25. 2 of those would do just fine...one to each board.

The specs state the amp9 can pull 10a but I would imagine this would be a dual channel paralleled 4 ohm load under some serious transient conditions to do so.

http://www.allelectronics.com/make-a-st ... PLY/1.html

(Sorry for the fragmented thoughts...wicked headache)


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PostPosted: 03 Oct 2008, 17:01 
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Location: Houston, TX
:twisted: I just got a 500W 24V supply from ebay for $40. Well, two to be exact :)
Lambda LZS-500-3
Only problem is they have a fan so I might stick them on the other side of the wall and make a DC jack in the wall so I can plug in without fan noise.
Anyway, the guy has I think 13 left. These retail new right now for up to 1400. Why? Who the heck knows but it makes it sound like a steal. They are used but in beautiful condition.
Ri

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PostPosted: 03 Oct 2008, 18:24 
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Why does the supply have dual secondaries? If I were to be using only one module would I just leave one set of wires unconnected?

Unfortunately I had the amp and toroid shipped to my home address, and my parents are too cheap to ship them, so I have to wait till the 23rd when my mother is making a trip up to get the parts... major bummer :(

In the meantime I was going to try to get the preamp/switching unit built, and look for a suitable enclosure.

Maybe what I want is just not done but I think the best way to describe it is a surround mixer. I'd like to have a few stereo inputs that are connect to the 4 surround speakers (R -> FR,SR; L -> FL,SL) and the sub. In jury-rigging an old reciever I found that outputting the full frequency range to a subwoofer-sized speaker pretty much gets the job done, without any low-pass filter action. Although it wouldn't be too hard to build a low-pass into the surround output circuit so long as I know i'll always want it (or i could pass it through a switch). In any case I want to be able to hear two signals at once through my sound system and would rather not rely on the computer as a mixer, since I need to have the screen up to change volume levels. If possible I'd like to have just a few knobs on my "signal handler" (i won't call it a preamp because I don't think I'll be needing to actually amplify the signals)

Anyway I'm wondering how I would go about figuring out how to wire this. I think I understand the circuit theory involved (make sure the signals stay in phase and have a common V=0) but i'm probably hazy on how this applies to audio signal. As far as my knowledge goes, if you super-impose two audio signals (connecting them in paralell to the amp input) they should mix at full volume and become one signal (as if you were using an adapter).

Like I mentioned with my current system having the weird volume issues I guess that is not always the case. Like I said earlier I don't want to switch between inputs, I want to mix them together (possibly all at once) on the device.

The way i envision it as a KISS (keep it simple, stupid) design is every signal input sharing a common ground with the output, and attaching a potentiometer to the "hot" wire connecting that specific input to the output ports.

Another, unrelated question:

What I've ordered so far is the transformer and the amp kits, but I left the enclosure to (make it up as you go). I'm starting to look for what I might use and came across the (important) question of heatsinks. First of all, most of the times I've seen amp parts using heatsinks there has been some thermal goo between the junction. I am also a DIY PC builder and have some Arctic Silver thermal grease left over from my last system build (this is used to make the junction between the CPU and its heatsink more efficient, the paste contiains something like 25% silver, as it is the most thermally conductive metal). Is this stuff applicable here? Or does the goo serve some other purpose? Also, do you think I could get away with using the heatsinks from my old system (pictured on page 1) for this build? I assume the efficiency of the heatsink is not quite so crucial for these amps as it is for microprocessors (If you don't use a rather large heatsink with a fan the chip will overheat and die very quickly).

Also: wire gauges. It looks like the transformer uses 18-gauge wires for both primaries and secondaries. Should I solder them to the board or get those little "crimp on" pins? Or does the kit come with those?

For the wires between components or the outputs and the plugs, etc, should I user thinner wires? Still 18-gauge? How about the singal handler? can i get away with say 22 gauge? 18 gauge might be a bit bulky for that.

I think that's all I have for now.

Oh I guess I should ask: I'd rather not pay radioshack's prices on all this stuff. They charge like 4 or 5 for an 1/8" jack which is a little absurd. If i bought everything from there I might end up spending the price of the toroid on jacks and wires! Can you guys recommend any electronic parts stores online that you have used in the past? I found that the links RiGuy gave me didn't have everything in the range of common shit everyone needs like some other places i've found.

One site I liked was http://www.goldmine-elec-products.com/default.asp

As well I liked this one that i found from google-ing electronics parts store: http://www.jameco.com/

others?


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PostPosted: 03 Oct 2008, 19:14 
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1. Transformer - Yep you would probably prefer the dual secondaries. It gives you a few different options in building a power supply. Use them both for full power.

2. Or does the goo serve some other purpose? - Use this stuff it will work well. I dont know if your chip is insulated or not. You should check the datasheet. It will tell you. I would assume its not if the datasheet makes no mention of an insulated package. If not insulated you will need a plastic sheet to insulate the chip from the sink. You can get these at radioshack along with a bolt and an acrylic washer for 1.39 if your store has the transistor mounting kit. Everything will be fine with no insulator if you have only one chip per heatsink and the heatsinks never touch each other or ground but not so fun if either of those happens.

3. I assume the efficiency of the heatsink is not quite so crucial for these amps as it is for microprocessors (If you don't use a rather large heatsink with a fan the chip will overheat and die very quickly). - Read the datashee but you dont need much sink with the T amp.

4. Also: wire gauges. It looks like the transformer uses 18-gauge wires for both primaries and secondaries. Should I solder them to the board or get those little "crimp on" pins? Or does the kit come with those? - Dont know what it comes with. Those wires are fine. If you can.. use solder.

5. For the wires between components or the outputs and the plugs, etc, should I user thinner wires? Still 18-gauge? How about the singal handler? can i get away with say 22 gauge? 18 gauge might be a bit bulky for that. -22AWG is fine for signal. 18 will be fine for everything else.

6. I found that the links RiGuy gave me didn't have everything in the range of common stuff everyone needs like some other places i've found.
I found www.allelectronics.com and its a great site with super pricing.

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PostPosted: 05 Oct 2008, 15:46 
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wouldn't putting plastic between the chip and the heatsink kind of defeat the purpose of the heatsink in general? If you insulate the chip electronically doesn't that also inslulate it thermally?


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PostPosted: 05 Oct 2008, 15:57 
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There are many insulators that insulate electricity but conduct heat.
Mica is one of them. If you have the uninsulated chips you must insulate them if they are to be on the same sink or if the sinks may have opportunity to touch or if the sinks have opportunity to come in contact with GND.
Ri

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PostPosted: 16 Oct 2008, 20:27 
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So i got the kits, and they're built!

Sorry I wasn't able to include any part-way pictures, but I did the majority of the construction at the engineering workshop between classes, etc so I didn't have my camera on me.

I made a few mistakes while soldering (including putting the surface mount diodes on backwards which i didn't realize i had done until the whole thing was built meaning I had to remove one of the capacitors and... well it was a headache in any case

So needless to say I'm nervous about whether the thing will actually work and I'm wondering what everybody recommends for testing their devices. Jan sells a "test kit" but i figured i'd be able to put something like that together with what's sitting around in the workshop.

I've made a username on the 41hz.com site forum and have asked some questions over there but I thought i'd keep this thread fresh.


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PostPosted: 16 Oct 2008, 22:58 
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Good stuff. By test kit, do you mean a DIY Speaker Dummy Load?

Cheers

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PostPosted: 27 Oct 2008, 22:28 
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So, whats the update? Did you get/build a test kit?
Ri

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