|Class D Switching Power Amplifiers and Power D/A conversion|
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|18th February 2007, 08:24 AM||#1|
Join Date: Dec 2006
Finalizing designs in sketchup
Alright so I had a free evening to sit down in a CAD program and hammer out placement and space issues with a soon to be built preamp/ power amp/ computer case
I'm using a few ESP projects to do this one. I don't care for balance controls to be honest so all I want is the input selector and volume. I'm using Hammond Electronics torid transformers in both the preamp and the power amp. They seem like good stuff so why not and I can actually get them fairly easily here. They also aren't too tall or anything which I like.
I plan on erecting a slim wooden separating wall by the power supply and then wrapping it in some foil. Maybe balsa wood so itís not very heavy and will be easy to get in thin strips.
I've decided that an active crossover might be in the mix for later. I wonít do it right away, but what I do want is access to a regular passive out so I'll just find a little switch I can put below to divert the signal. Another switch would be good to turn off the active crossover's opamps.
I wanted to leave room around the pre-amp in case I do wacky mods or threw stuff in there later.
Headphones jack at the front. I ran across a forum post on ESP as to where I should inject this plug into the preamp. I'm tempted to do a switch for this, but the power amp has its own switch. I'll probably do it just because.
Oh yah, in case you're wondering what the hell those DB15 plugs are for. I hate extra wires out the back of anything, I love cat 6 500/550mhz cable, I love making my own stuff. I plan to make a stereo cable with some shielding and such, either a foil filled or cast metal hood to terminate it. I was going to use cat terminals but they take up way too much room, but I wanted a solid tensioning, so why not a serial style plug? Its high enough density, slim, has a thumb screw lock on both sides of the plug, seems like a good idea. Also the soldering of many wires into a single point is frustrating. In the end this is my system and isn't meant to be mixed with anything else so I don't care.
The power amp, I plan to use a pair of UCD180 ST modules to start with, when I feel comfy with my build and when I can get them I want to put in LM4562 opamps to spice it up. I was thinking that since my electronics knowledge isnít that great I might just buy the Hypex HG PSU because it has the DC protection and other neat little features I could never cram into a neater shape. Its one of those issues where my own build would be underwhelming.
I decided that an extra 7$ would be well spent on bigger transformers. I was aiming for a 160w 30v/15v since my speakers are 6ohm and I can get away with it just barely. But instead I figured, ah hell 9$ and super size it to a 230w. It was maybe only 1cm larger in height/ diameter.
I wanted to run the power cables up the centre to the switch at the front then into a soft-start module then back down to the rear of the amp. To be sure that the outputs can handle the current I figure a db25 will be fine, thatís a huge pin count and leaves me with room to use more wire or do whatever I need to. In the meantime though I'll bridge the unused pins.
In my listening tests with cat6 terminals/ cables on a modified class A (Kenwood KR-V106A) I found that 2 cables helped push out the more complex music. Very high and low ranges didn't fall out. It wasn't a huge difference but it was enough. So I'll have 2 cables per output. My speakers in progress are much more power hungry than before so it should be fine.
I wanted the design to shorten all of the signal wires. Running a length of power cable up the front and seems like the least of my worries. I was also thinking of an alternate placement for the UCD modules might be the back plat, but if it makes too much heat it would mess with the output plugs.
I decided to go with rack mount chassis from Jaycar electronics because well, the price can't be beat. A shop here sells the same cases but they charge $90 for the 1u and Jaycar sells it for $35.
comp case back
comp case front
Simple enough designed for a Matx mobo. The power supply is a passive external dual brick design (picked it up in Japan last summer). I'm waiting for DTX mobos and new directX 10 cards before doing this one. The sound card is an SE-90 Onkyo wavio. Very nice transparent card I also picked up during the summer. It was a good upgrade from my M-audio Revolution 7.1.
The HDD is suspended via 4 posts and elastic bands like in my current franken-rig. It goes a long way to soften it, but itís so hard to find a good spot for it. Having the DVD above it helps turn it into a faint crumble while defragging, but I need a small slow fan nearby since itís out of the way and does get hot. (Seagate 7200.10 250 GB)
This system isn't a media centre PC. Itís just a silent rig for emulators, silent hill games, music and a few DVDs. I would like to make them all rack style and build a little cab to stock them in. would be nice and organized.
I plan to sodder in a custom db15 cable to the sound card like the rest of the audio system has. This also gives me the chance to make a balanced circuit. I think when I do the opamp upgrade later I will invert in anther ESP project, the balanced transmitters/receivers for the 2x db15 patch cables.
So thatís the jest of my design. Any ideas on what could be improved in the layout? Thanks for reading. Now to work on my speakers, got to find room for a 15" woofer ><
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