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Project: M³ home studio speaker amp (now finished!! pics at page 10) - Page 2

post #16 of 153
11/19/09 at 9:05am
Quote:
Originally Posted by Jaypee View Post
My current speakers are low-cost silverstone 220. Impedance=4-8Ω(no more specific info found), sensitivity=88dB. If I'm happy with the build, I might concider upgrading my speakers to match the quality of the amp.
If that is the case, then make sure you build the amp properly. Don't skimp on parts! You should *seriously* consider placing an order with Mouser to get all of the good, recommended parts.
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post #17 of 153
11/19/09 at 11:20am
Thread Starter 
Quote:
Don't skimp on parts! You should *seriously* consider placing an order with Mouser to get all of the good, recommended parts.
The parts I've looked into are not b-grade. Most of them are equal to recommendations, the few parts mentioned earlier are not found from Finland, and that's why I was looking for a substitute for them. The only reason I'm trying to find parts locally, is to save money on shipping costs. That been said, I still might look into mauser, wether the total sum would be less anyway (since I think parts in Finland are more expensive in general).
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post #18 of 153
11/19/09 at 11:26am
As a guide, back in Australia it was cheaper to buy from Mouser and pay for international shipping - even if the order was only $75. The parts are *that* much cheaper.

You could order from their Finnish site, pay in Euro, all customs and duty fees covered, with free international shipping on orders over 75 Euro.

http://fi.mouser.com/
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post #19 of 153
11/21/09 at 9:08am
I live in Italy and am planning to build myself various stuff.

Shipping from Digi-key was 18, mouser was 20 and Farnell was only 9 euro so you could try looking into them...
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post #20 of 153
11/25/09 at 6:51pm
Thread Starter 
What do you guys think about mounting the MOSFETs offboard? Meaning if I'd make off-board heatsinks on the sides of the case, attach the transistors of the M³'s to them and use wire to track their feet to the pins on the circuit board. Would the distance between the transistors and the board be harmful?
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post #21 of 153
11/25/09 at 7:22pm
Quote:
Originally Posted by Jaypee View Post
What do you guys think about mounting the MOSFETs offboard? Meaning if I'd make off-board heatsinks on the sides of the case, attach the transistors of the M³'s to them and use wire to track their feet to the pins on the circuit board. Would the distance between the transistors and the board be harmful?
Probably not a good idea. I am not sure but I think I vaguely remembering Ti mentioning not to do that with this board. Hopefully someone else will confirm. The M3 really not designed to be a speaker amp. There are much better designs for that application. A hammer is a great tool for a lot of things, but is not such a good tool for screwing in a light bulb.
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post #22 of 153
11/25/09 at 7:28pm
Quote:
Originally Posted by Jaypee View Post
What do you guys think about mounting the MOSFETs offboard? Meaning if I'd make off-board heatsinks on the sides of the case, attach the transistors of the M³'s to them and use wire to track their feet to the pins on the circuit board. Would the distance between the transistors and the board be harmful?
The wire is a bad idea.

Best you could do is mount them underneath the board. But really, unless you are going for a properly heatsinked case the the HiFi2000 Dissipante, I doubt it will be that much better than the onboard sinks. You are still running a LOT of power through a single pair of devices.

*

Did you end up looking at Mouser?
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post #23 of 153
11/25/09 at 7:32pm
Thread Starter 
Quote:
Originally Posted by m1abrams View Post
The M3 really not designed to be a speaker amp. There are much better designs for that application. A hammer is a great tool for a lot of things, but is not such a good tool for screwing in a light bulb.
I hear you... however a lot of parts are on their way already, so I'll build this project as well as I can. If this doesn't work out, a lot of you will have great "I told you so"-moments, I'll be a bit more poor financially and a lot more rich in experience.

But then again if it does sound anything like I've planned, I'll be a very happy camper.
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post #24 of 153
11/25/09 at 7:39pm
Thread Starter 
OK then.. I'm thinking about mounting 51mm (2") onboard sinks, and might also connect them to a larger sink on top.

Quote:
Originally Posted by Beefy View Post
Did you end up looking at Mouser?
Truth be told I don't have enough money on hands to order all the parts at the same time now, so I haven't even checked the total from Mouser. I think I'll order them in a couple of weeks when I have the cash. I did, however, manage to get a fair deal on the transformers, 2*15V 40VA.

EDIT: A quick 3D model what 2" heatsinks will look like on an M³ board

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post #25 of 153
11/25/09 at 8:54pm
you could always custom machine a block of copper to snugly fit all the mosfets then connect that block to an exterior heatsink...the possibilities are endless.
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post #26 of 153
11/28/09 at 9:24pm
Thread Starter 
Quick question: I'm going to raise the total C7 capacitance to 6000μF (6x1000μF) as recommended, does leaving the ground channel unpopulated affect the total capacitance of C7 or C8?
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post #27 of 153
11/28/09 at 9:38pm
No, those are all "ballpart" recommended capacitance figures, and leaves a lot of room for variations. With that much capacitance, though, you should use a heavier-duty diode for D1.
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post #28 of 153
11/29/09 at 5:10am
Thread Starter 
Quote:
Originally Posted by amb View Post
No, those are all "ballpart" recommended capacitance figures, and leaves a lot of room for variations. With that much capacitance, though, you should use a heavier-duty diode for D1.
I've wrote on my shopping list 1N5401 for D1 rated 3A.. should I go with an even bigger diode?
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post #29 of 153
11/29/09 at 6:39am
1N5401 is fine, but its leads are a bit too thick for the PCB holes, so you'd need to mount it creatively. Alternatively, you could use a diode in the TO-220-2 package and spread the leads out slightly. A good example is the 10TQ045 (Digi-key VS-10TQ045PBF-ND), a 10A 45V schottky diode.
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post #30 of 153
11/29/09 at 11:27am
Quote:
Originally Posted by Jaypee View Post
I've wrote on my shopping list 1N5401 for D1 rated 3A.. should I go with an even bigger diode?
You will already be buying 8 MUR820 for the two S11's, so why not use a couple extra of these? Depending on where you buy, you might get a quantity price break at 10 pieces.
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