Apox digital X-over

[tcpip]

As an example of the kind of hardware and internals that are also called PCs these days, check out the Hoojum Cubit P4. It even has the hunk of thick aluminium to block all them Evil Microphonics which all Real Audiophiles are so concerned about. Of course, for any digital xo work, you'll probably want to add your own sound card hardware... but it's a great starting point.

In fact, if the digital filtering is done in the user state outside the kernel, on Linux, like with BruteFIR, then you can even give a menu of sound cards for the customer to choose from.

Another product range to drool over is Hush Technologies' boxes. More than enough compute power to do a lot of digital filtering, and totally fanless and silent. And looks great on the audio rack too. One of the models, fully equipped with CPU, RAM, HDD, and CD-ROM drive, is available for EUR 666.00. And their boxes are also available in black, and you can show off all them heatsink fins and hint that you're using "Class A digital filtering."

Tarun

[Da5id4Vz]

In the Mini ITX world the Shuttle SS-51 has been getting very affordable. Outpost (Frie's Electronics), MEI Microcenter and Tiger Direct all carry it. Its worth checking out on the Mini-ITX Website. It uses fan less heat pipe technology to remove heat from the CPU.

Nice little aluminum box to.

-Dave

[dc]

I've been looking into a similar project for a few months now. Wanting a Windows-based solution and not knowing how to program, I found a graphical programming language called Max/MSP, which I believe could be used to create a multi-channel convolution engine (to implement DRC, or Digital Room Correction, a freeware program available on freshmeat and discussed on the htpc section of www.avsforum.com and also at the hifi_dsp Yahoo! group (btw, there are people at both of these groups who are interested in a project similar to the one being discussed in this thread). Max/MSP would also allow for the implementation of user-defined high-order, linear phase xo and time delay per driver. I have no idea how much computing power this would take, though.

tcpip, you've written that the hush technologies box (a Via 1 ghz, if memory serves) is more than enough power.... More than enough power for what? I'm looking for enough power to process up to 16 paths (6 channels total - 2x4, 1x3 and 1x2) of high-order, linear phase filters.

Also, several people have mentioned BruteFIR and Linux. I'm a fan of both, but, there are some limitations. For instance, there are no Linux drivers for my Lynx Two-B soundcard. Also, for those who would use the PC as a front-end (music jukebox, DVD player, etc.) Windows programs and surround decoding algorithms are years ahead of what's available on Linux.

[MWP]

Windows programs and surround decoding algorithms are years ahead of what's available on Linux.

Years... i wouldnt be too sure of that...

But we shouldnt be looking at taking the HTPC path here...
This project should be confined to a nice active xover, room eq... thats it.

I say forget ADC/DACs as as said before, youll never please poeple this way... everyone has thier opinions on what DAC sounds better, etc.

So, stick with:
SPDIF In -> EQ -> XOvers -> 6/8 SPDIF Out.

This will keep things nice and simple, and also help keep the cost down for us poor guys

[dc]

I guess you can look at my statement two ways... I didn't necessarily mean that it will take years for Linux to catch up to the current state of Windows, but, I did mean that Linux is now where Windows was years ago. More development is being aimed at Windows. If what you're looking for is simple a Linux box with spdif in and out, I think the solution already exists - BruteFIR on a Hush box with the appropriate soundcard (maybe RME makes something? There are Linux drivers for most, if not all, of their cards). Creating a Windows based solution would be much more of a challenge, but would allow use of the Lynx Two-B and AES3 ins and outs (Lynx makes a 16-channel AES3 card - the Lynx AES16). Or, use the DACs on the Lynx, which have repeatedly been positively compared to the best standalone DACs available.

[tcpip]

Originally posted by dc
tcpip, you've written that the hush technologies box (a Via 1 ghz, if memory serves) is more than enough power.... More than enough power for what?

I asked questions about computer power in a thread I started and the answers surprised me. I found those responses quite eye-opening.

I'm a fan of both, but, there are some limitations. For instance, there are no Linux drivers for my Lynx Two-B soundcard.

Personally, I feel that we may not suffer in spite of lack of support for some of the high-end cards for this application. Already, others seem to feel that we need only digital in/out, in which case probably lower-end cards can do. Or else go with some of the supported high-end cards, either supported by ALSA or OSS. Anything special I'm missing about the Lynx Two?

Also, for those who would use the PC as a front-end (music jukebox, DVD player, etc.) Windows programs and surround decoding algorithms are years ahead of what's available on Linux.

DVD playback yes, because of the conflict of open source and CSS. But for just audio playback, I don't see any constraints at all. And for this box, we are not talking any front-end. This is supposed to be a "standard black box in the audio rack", which is programmed over USB (or Ethernet?) from another PC. That PC can run any OS it wants. So for this box, what's the constraint?

Originally posted by MWP
But we shouldnt be looking at taking the HTPC path here...
This project should be confined to a nice active xover, room eq... thats it.

For whatever it's worth, I agree.

Tarun

[dmfraser]

I have used this device to implement a 2 and 3 way digital crossover and had great results. TI's software is a little clumsy to use but the device has preformed as well as the A/D and D/A converters and analog ground scheme allow it to. Just make sure to run it at 96 KHz.

The advantage is that TI's software supplied will allow you to implement all the functions, with no programming even though it is clumsy and there is a bit of a learning curve.

Also, their software, on the CD I got with the evan board does not support burning EAPROMS. However, I nagged them and they sent me a build that does support EAROMS to run the thing is master mode.

If anyone writes any additional software for operating this DSP, contact me at dmf@renkus-heinz.com. We might be willing to buy it.

[netgeek]

I've been playing around with a "paper design" using the TAS3103 for a short while and it appears to be perfect for my application (a 3-way powered speaker with provision for room EQ and other features). I don't have an eval board (yet) but I'm wondering just how dismal the software/development support might be for this device (?)...

Compared to a pcb stuffed full of op-amps and many, many configuration options (e.g. phase alignment, notch filters, etc.) this device might make the ideal "black box". It would take care of the immediate xover, slope, phase, and EQ-fixits required for a given enclosure/driver design and (even better) would allow for later room-EQ and other tweaks in real installations. And all this without the need for a multitude of high-tolerance matched components made of "unobtainium" and the endless fiddling that real world "tuning" involves.

The real challenge, if it's to be useful in the DIY world, would be in creating a decent software package (and GUI) which would allow the user to easily take advantage of all the device has to offer and to then download and test the results. Not easy! But worth it, if it can be done.

Count me in if anyone wants to pursue a widget based on this approach - otherwise I'm off to bash on the thing on my own ('cause I think the potential is too great to ignore)....

Regards,

Bill

[WTS]

Hi; Great Idea. Although I'm not a programer, I'd love to have something like this in my system. Analog based xovers just doesn't cut it, personally, I think any opamps in the signal path doesn't cut it. I was on Ti's site yesterday and I noticed this device and I was thinking the same thing, will it work. I'm not sure, but does it have what it takes to be in the audiophile class though.

[Fred Dieckmann]

"Analog based xovers just doesn't cut it, personally, I think any opamps in the signal path doesn't cut it."

"SPDIF In -> EQ -> XOvers -> 6/8 SPDIF Out.

This will keep things nice and simple, and also help keep the cost down for us poor guys."

You don't have to use op amps. A really good sounding SPDIF interface is much more difficult to design than an analog stage. A simple Spice model is much easier to write than software. You can model the driver rolloff and crossover slopes pretty easily as a starting point for crossover adjustment. There are also programs for hobbiest to model speaker response curves and passive networks to get the desired crossover slopes. Copying the transfer fuction with an active nework after that is not as difficult as you would think.

Which do you think has the easier learning curve and is the path of least resistance? For a decent design the question of which will sound better is a given...... analog, even with some of the better sounding op amps if designing discrete transistor circuits is not your thing.