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currentkills91

Fri Apr 06 2012, 05:41PM

Registered Member #3831 Joined: Thu Apr 14 2011, 02:54PM
Location:
Posts: 265

Hello guys, I have previously made a thread about wanting to build an amplifier for my car's subwoofer. Well now I want to make another amplifier, but this time for my room. It's gonna have two 50W channels for left and right, and a 200W center channel for the subwoofer. Now the amplifier part is not the problem, as I'm using TDAxxxx chips.

I am using an old cassette deck I bought as the case, and sadly there is no real room for the transformer I have. My question is, is if you guys think I'd be able to fit a decent SMPS in the available area, I wanna make it capable of around 500W so I have plenty of available power.

Here's a pic so you can see my available power supply space, the little plate with RCA jacks are on, from the edge of the semi-circle to the other edge, or about 3.5x3 inches, and about 4 inches tall (8.9cm x 7.6cm x 10.1cm)

I looked around 4hv and couldn't find anything on this SMPS -here- maybe I missed one? Has anyone built this one before, and if so any problems besides the "to be expected" ones?

This is the SMPS I'd like to use as it's simple in design but looks promising. I have an ETD39 core laying around I bought off eBay, that site says an ETD39 core should be good for >350W supplies, but can it handle 500? I also seen Uzzors2k's SMPS and he used a 60 turn primary for 230V operation, I live in USA, and we have 120V here, so I should be able to get away with 30 right? Although I would probably do 45 to be safe, if it sounds like a better idea?

Now I don't wanna open a new thread to ask this question, so hopefully nobody minds I put it here. In this pic you can see the holes in the case where the tape players function switches use to be, Record, Play, etc. Any ideas on what I should use them for? I can't think of anything off the top of my head. The big space where the cassette itself use to go I will use for an LED audio spectrum analyzer.

Forty

Fri Apr 06 2012, 07:02PM

Registered Member #3888 Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649

In the project page for uzzor's smps, he's got an excel spreadsheet that is very handy for designing the transformer. The 4"x4" footprint is pretty small, but with the 6" height, you could probably stack two boards on top of each other (one for the high power stuff and one for the control circuitry I imagine.)

What kind of voltage output does it need?
A modified computer power supply might be able to do the trick (you'd need to find one of the atypically shaped ones to fit into your allowed space)

currentkills91

Fri Apr 06 2012, 08:26PM

Registered Member #3831 Joined: Thu Apr 14 2011, 02:54PM
Location:
Posts: 265

I actually measured the space and its only 3.5 x 3 x 4, so It's gonna really be tricky, but I think if I do 3 levels I can fit everything perfect. First layer will be the control circuitry, second layer will be the high power stuff and transformer, and the third layer will be output filtering and voltage monitoring circuitry. I need -50V, -25V, -15V, 0V, +15V, +25V, +50V for the amplifiers. The +- 15V I can get from a regular transformer probably, cause I think I have one laying around.

The +-50V for some TDA7293 chips for the sub amp, and It's still a debate, but I'm probably gonna use the LM3886 for the left and right channels, and that's where +-25V comes in. Although the TDA7293 high efficiency circuit modded for ~50W output might also work. The +-15V is for the pre-amplifiers, tone control, subwoofer LPF circuit, the spectrum analyzer, etc. etc.

I wonder if it would be worth it to go with surface mount parts? Hmmm...

klugesmith

Fri Apr 06 2012, 08:26PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

currentkills91 wrote ...
My question is, is if you guys think I'd be able to fit a decent SMPS in the available area, I wanna make it capable of around 500W so I have plenty of available power.

How about if you start by browsing electronic distributor catalogs, to see the size (and cost) of comparable off-the-shelf SMPS units?

Or look at PC power supplies of comparable power.

currentkills91

Fri Apr 06 2012, 08:42PM

Registered Member #3831 Joined: Thu Apr 14 2011, 02:54PM
Location:
Posts: 265

I would buy one, but finding one that fits my needs would more than likely be expensive, more expensive than building one. I can get all the driver circuitry, and the mosfets, for about 20 USD. The transformer core and form was like 8 USD from eBay. I have the rectifier diodes, pulled from an old SMPS that wasn't mine, so free besides labor of removing. I have all th wire scavenged, so once again free besides labor. So for about 40 USD in total for everything, I can build a 500 SMPS which supplies the voltages I need. So it's just more practical to build one, thanks for the help though! It's definitely appreciated!! :)

klugesmith

Fri Apr 06 2012, 09:57PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

Sure. I just pointed to commercial SMPS units as reference for the
physical size and complexity of practical realizations in that power range.
Including bells and whistles such as PFC, surge suppression, and EMI compliance.
-Rich

p.s. Is it OK to maintain, after 40 years,
a fascination with making rather than buying?
Fixing rather than replacing?
Worst of all, acquiring things when they are free or are good deals, when there is no immediate need for them?

currentkills91

Fri Apr 06 2012, 10:18PM

Registered Member #3831 Joined: Thu Apr 14 2011, 02:54PM
Location:
Posts: 265

Yeah, I just need something basic, and if I go with surface mount, I could get fit alot more features in the same are. However I would have to get someone to do the boards for me as I don't have the proper tools to make them myself. All I need is something to give me a 100V supply with the taps I need. If I can fit it in there I'll add current limiting, other than that though, no special tricks.

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