$30 Active Line-Level Crossover - diyAudio
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Old 15th July 2003, 05:08 AM   #1
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Default $30 Active Line-Level Crossover

Serious. The Soundblaster Live! 5.1 has an EMU 10K DSP chip on it, and can be had for ~$30 at good retail outlets. This is the same chip that is used in $600+ pro DSP units, the only difference being codec choice, and marketing tactics! Today I got one for the sole purpose of using it as an active crossover, and guess what? It works, and works well.

STANDARD DISCLAIMER APPLIES: if it doesn't work for you, it just means you're a guru of a different color, and it's NOT MY FAULT. If you take on this project, be aware that there is HUGE potential for success in store, but also huge amounts of potential frustration, and that you go into it of your own free will and choice.

You will NOT be able to do this with the drivers that come with the card. Thus, it works like this:

1. Buy the card.
2. Throw away the CD that comes with the card. Or use it as a clock, coaster, object of religious and/or sexual interest, or what-have-you.
3. download the kX driver set from http://kxproject.spb.ru/index.php?skip=1 .
4. Install the card and drivers.
5. Gnash your teeth for a week or so while you tweak settings in order to get the @!#$ drivers working properly. You may not skip this step. :-P
6. USE A DIGITAL RECIEVER OR OTHER SOURCE to send your signals to the soundcard. Do NOT use the line-input. It uses the noisy, inferior, WHY-OH-WHY DID WE EVER USE THAT, AC97 codec to bring in analog line-level signals. Yuck! Fortunately, you can, fairly easily, get 6 channels of digital sound into the card.
7. Use the DSP program for the kX drivers to route your digital inputs through "freq splitter" plugins (or, if you're clever, write your own DSP code to do this) and then route the outputs to either the digital outs of your card, and then to a digital reciever / amp, or the analog outputs, and then into your amp.

While the controls aren't super-precise (I can't figure out how the slope adjustment works exactly, and it doesn't correlate to a filter order or dB/oct figure, I just know I like a setting of 3.0...) it does allow you to play with the crossover point with superb accuracy, and the tweaking is free, and requires no soldering!

The downside is that you have to have a computer running in order to make this happen. I'm working on that though. I'm thinking that perhaps, a $50 pro-level DIY DSP unit could be built based around this chip and the I2S codec, with 8 channels of input and output, digital and analog. If all else fails, you could do something REALLY crazy (like run the PSU for the computer fanless, and the CPU, and just use really huge heatsinks) in order to get that blessed silence you need in order to really enjoy your music.

Just thought I'd let you all know, this works really well, and I hope it can be of some advantage to someone else.
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Old 15th July 2003, 10:43 PM   #2
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pretty cool.

$30 + $1000 for computer ?

/hehe
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Old 16th July 2003, 12:17 AM   #3
cowanrg is offline cowanrg  United States
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hehe, details, simply details.
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Old 16th July 2003, 02:15 PM   #4
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Hah, good point...

Though, you could get all the supporting parts for under $300, I think... just a cheap integrated motherboard / CPU / RAM / hard drive / CD-ROM + case, or an e-machine...

Or! Maybe one of those new Small Form Factor machines! That would be cool.

I guess the thing that's so exciting for me is that now I have three VERY powerful DSP engines in my computer and they all cost me less than $50 each. (I bought the first two a while ago, before the price dropped.)
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Old 16th July 2003, 07:23 PM   #5
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Waauwwww, sounds good. I'm really fasinated by the utility of such a project. Please keep us posted.

Regards,
Thijs
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Old 16th July 2003, 09:05 PM   #6
Vikash is offline Vikash  United Kingdom
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A digital active crossover using an old machine that's lying around and a cheap sound card...sounds very interesting.

Although I think having to wait for it to boot will be more annoying than getting rid of the fan noise

I have no practical experience with crossovers, so im curious as to whether this method would be comparable in output quality ( ie. ease of playing with digital slopes and crossover points etc. aside) to just a normal active analog crossover, considering the the cheap analog output connectors and (probably) mediocre DAC on the sound card?

Quote:
I'm thinking that perhaps, a $50 pro-level DIY DSP unit could be built based around this chip and the I2S codec, with 8 channels of input and output, digital and analog.
You've got my attention. I'd like to see if anything develops on this...
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Old 16th July 2003, 11:25 PM   #7
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Okay, here's the really aggravating thing, having played with it for a while.

The outputs on the card have pretty nice DACs, and I can fully exploit the 96 dB dynamic range that 16-bit gives to me, using these DACs.

Unfortunately, the *inputs* absolutely SUCK! Yes, there are digital inputs on the card, and if I used the digital inputs, I could have 6 channels in instead of 2, and better SNR, but the AC97 codec's ADC absolutely blows green chunks!

Is anyone out there knowledgeable about ADC's etc? Pro ADCs are horribly expensive, and I can't imagine that it's actually that expensive to produce a quality unit... Anyone know the answer to this?
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Old 16th July 2003, 11:43 PM   #8
Vikash is offline Vikash  United Kingdom
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Did you pick the SB (or EMU 10K should I say) because you can get drivers to do what you want?

I was thinking that there are many other budget cards, probably with a lot better ADC's and DAC's and less fraught with Creative's lies about its capabilities (not an SB fan, can you tell? ) that could be of use.
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Old 16th July 2003, 11:55 PM   #9
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Well, the card is extremely capable.

Have you seen the kX drivers? In all seriousness, if you want to jump into the microcode on the chip and rewrite it, you can. Yesterday I had a LOT of fun, making a feedback loop with my mixer and the soundcard, using the soundcard to make a transposer effect. The end result? I don't know how to describe it, but it sounds like something off Star Trek.

Plus the digital crossover. Plus the high-quality MIDI synthesis. Plus the multitrack recording capability. Plus the reverb, echo, chorus, distortion, tube sound, and other effects that haven't even been written yet. All this for $30 a pop.

The only two downsides are (1) the sucky ADC on the card (I wonder if I could just shield this to make it better? Hmm.) (2) the lack of good synchronizing capabilities. (The cards drift out of sync at an absurd rate.) I'm wondering, seriously, could I design and build an 8-in 8-out (or maybe even 16; I think the chip would support that) DSP unit based on this chip, and price it reasonably? Failing that, can I at least get an inexpensive ADC that won't take my noisefloor up to -40 dB?
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Old 17th July 2003, 12:09 AM   #10
Vikash is offline Vikash  United Kingdom
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Am I right in assuming that the outputs from the card go straight to a power amp? I.e the card is the pre-amp stage?
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