There comes a time when you just want to build the whole thing. I recently read about a DIYer who built a three way enclosures with Vifa Drivers. For space saving it would be the perfect enclosures to build the amplifier in it. Since Adam McCall got beautiful results I decided not to reinvent the wheel and build from his plans.
But why just one amplifier ?
Active Crossover, Class-A 20w Tweeter Amp, Class-AB 50w Full Midrange Amp, Class D 200w Woofer Amp.
Stay Tuned
As you may or may not know I’m building an audio/video pre-amplifier/pre-processor. Since this a quite a bit DIY project I decided to make it very modular.
It will accept either SPDI/F coax and optical as input along with the more basic analog inputs. Every input module handle one input and will output an I2S signal over a 5 pin header (4 for I2S and the last bit will be for if audio is present). Every input will then go to a mux board which will simply be relays controlled by the main logic board (possibly by some simple PIC) this board will have only one output and will be I2S. Exception to this will be the SPDI/F inputs; the CS8416 in software mode will be responsible for the mux and the output will then go to the mux board.
The fun stuff will be on the main board; the I2S input will go into a SRC (Sample Rate Conversion) the output will always be at 24-bit 192kHz and will go into a DSP. The SRC will be pulled into bypass if the “audio present” bit is not present – this will allow me to pass raw SPDI/F data and possibly implement AC-3. The main control logic will be a Freescale Coldfire MCF5282 at 80Mhz and will possibly interface with a Freescale DSP56367. The Coldfire will handle the infrared, the VFD display the power (ON/OFF), programming the DSP and monitoring the pre-amp for over-temp and such.
The video will follow the same pattern; Inputs will be converted to digital, will be muxed and then back to analog for the output – however I will not put a DSP in the single path. This project is already complex as it is.
For the power I decided to keep it simple and will use a ATX12v power supply.
Right now, the output PCB is done and I’m designing the main board. Fun stuff !
Version 2
Features more space and place for bigger heatsinks. I also added a balanced input driver (INA137 at -6dB)
It’s one thing to build and amplifier, it’s another to build a pre-amplifier. I selected a CS4398 [PDF] as DAC; this chip has a differential output for both channels, an I2S input and up to 120dB dynamic range.
What’s nice is that Cirrus Logic made a very well designed evaluation board for this chip, the CS4398. I’ve used the XLR output as a starting point for my own output stage.
The DAC will run at 96kHz with an oversample of 512x. The master clock is just over 49MHz (49.1520MHz). The input (I2S) will be feed from either a DSP or my “Core Module”; I have not yet tested if the ColdFire v2 @ 66MHz will be able to keep up with video & audio. As for the PCB, all the components will be surface mount to minimize space and keep the trace length to a minimum.
Well I just finished my PCB layout for one of my class A power amplifier;
I will now attack the blanced input stage. I was thinking about a simple op-amp with a buffer right before the “input”.
More people watch and vote for American Idol then the presidential elections. Why are we sitting and watching ?
Furiously dialing, spending money on this staged democracy, for the next diva of music; at least for a handful of years. For a moment it creates life on our couches; a temporary expression of vitality. Our desire to see one hero, beaten, stabbed to death, triumph leaving a trail of destruction behind is, perhaps, the only emotion that allows us to delay the unthinkable while we wait on our couches to die.
To have one’s birth certificate expire one has to have one. Is it still possible to think about yourself ? If one think, since one think one is, what happens when one is unwilling to stop and think ?
Cats are remarkable, one second they are on the floor walking. Then they jump 4 feet in the air onto a tiny ledge that runs along the bottom of a window and continue to walk just like nothing happened; you should try that, it’s not something you can just do. Yet, even a cat, agile as it is, doesn’t feel comfortable entering an empty new room.
So what does the cat do when it enters a new room ? It stops, all it’s senses seem gone; it’s processing it’s new environment. Then slowly, it will be able to jump on that ledge. But to get to that level it had to take time and explore. After a while you forget what it took to get there, it seems like second nature for the cat to jump on the ledge.
You need to take time and realize that you too had learnt some things that seemed impossible yesterday. Just touch your nose or feet; seems simple right ? You might not remember it but when you were born it wasn’t like that ! Now, to the novice it seems like it’s very easy and can be done without any practice; don’t be fooled because it looks easy. Touching your noise seems easy for you since you’re a master at that, you had years to practice, however to the baby it, while it looks easy, it will take years of practice. Now don’t get discouraged, you did, eventually, touched your nose !
To start something exiting you need to step out of your comfort zone.
Well I need a new past time, guitar, photography and living is not keeping me awake at night. So I thought I should connect my air conditioner on my local network. This is a simple project from the hardware point of view, the hard part will be the logic. The first step is listing my Inputs/Outputs, with this list I’ll be able to choose my micro-controller.
Inputs (10):
Outputs (9+):
I was able to get all this because I opened my AC:
Fun, they mixed 115v AC with 3.3v DC on the same board; what could go wrong ?
Basically the choses I have, for my controller, are:
The MC9S12NE64 is very nice since it is the only one that will fit in the current enclosure however it is a bit short on inputs/outputs.
Windows, Mac OSX all running on a Linux host with super eye-candy !
I previously had Debian Unstabled installed on this machine. But since I have nothing better to do, I formatted and installed Windows Vista… er no sorry, Ubuntu.
Well, I wasn’t that worried, everything worked fine in Debian – Suspend/Resume, Wireless, Sound. And Ubuntu ?
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Philippe "Yoshy" L-M — philippe (at) screenshot (dot) ca — ©2007
