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Old 12th January 2011, 01:51 PM   #171
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Originally Posted by simon dart View Post
I agree, that would be such a great thing to be able to do. I've been thinking along these lines for sometime but haven't seen a solution that really cuts the mustard yet. Just think of what you could do with a really high quality USB Transport - USB DSP crossover that outputs I2S - DACs - Poweramps. Not sure where would be optimum point to incorporate volume control.
First decide if you want to implement it in the digital or the analog domain. I would go digital, otherwise would be a pain to control 8 channels. You need 8 mono pots or 4 dual pots or any other similar solution. LDRs could be a solution, but matching 8 and 8 can be a bigger pain.
Going balance only doubles this problem

A solution would be to use a software volume before the transport, that is, the media player itself volume control.
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Old 12th January 2011, 02:48 PM   #172
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Hey guys, this is all very interesting, but not really in the scope for this module.

It is not intended to be a DSP. You can interface with a DSP if you like.

It is quite simply a USB Audio Class 2 Device with PCM and SPDIF output.
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Old 12th January 2011, 03:07 PM   #173
fb is offline fb  Australia
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Originally Posted by 5th element View Post
It depends on how handy you are with the DIY and how the retail implementation has been designed.

AD manufacture a board specifically for interfacing the DSP evaluation modules with sigmastudio. The board is basically a USB to I2C/SPI converter. If you could modify the retail unit so that you could get access to the control pins, then I am sure you could directly control the chip via ADs USB-I2C board.

SigmaStudio is free on request from AD, but they didn't want to release the firmware programmed into the USB to I2C converter. Naturally this means I'd have to buy theirs, if I want to guarantee success. It isn't outrageously expensive @ $99. Note that AD don't allow a company to provide SigmaStudio along with their product, the company would have to write their own software.

Sigmastudio will output the code that's actually used to program the DSP chip, in both hex and binary. So I am sure it wouldn't be too much trouble for someone competent at micro controller programming to write their own program that could upload the hex file to the DSP chip. Currently I know zero about programming, but I have a project coming up where I intend to learn!

The brilliant/interesting thing about the sigmadsp chips is that they aren't hugely expensive. I think the ADAU1442 will cost me something like 15 each? And to make a board with I2S inputs/outputs would require nothing more then the DSP chip, a few caps and resistors, a crystal, a voltage regulator, a E2PROM and the headers. So it's cheap and small seems perfect for TPA board

If you're intending on buying a retail product, to use with ADs USB-I2C module I will say a couple of things.

The 1442 can operate either with a micro controller sending it the code, or on boot it can grab the code from some E2PROM memory. The E2PROM memory isn't built into the chip and has to be provided separately, but once in place it will allow the chip to self boot, without the need for a micro controller. (Instead of the micro sending the 1442 the code on boot up, the 1442 grabs the same code from the memory instead. You have to select what boot mode you want to use by altering the state of one of the 1442s pins.)

You would have to make sure that the retail product is configured in the correct way, or that you could modify it to be, otherwise it'd be a pain to use. Do you know of any retail products that work around the sigma chips besides the minidsp?
I don't know any other retail products. I was thinking more along the lines of whether or not low-level DSP programming was required for a finished (retail or DIY) product.

Having just spent hours and hours laying out my first set of PCBs for a Midibox project, I'd be having a shot at my own ADAU1442 board if I wasn't rather scared of soldering a chip with 0.5mm spacing between its pins.

If the SMD soldering were magically done it's not hard to imagine a cheap and easy digital only DSP board booting from E2PROM, and the firmware done in Sigmastudio via AD's USB dongle.
 
Old 12th January 2011, 03:46 PM   #174
Goto is offline Goto  United Kingdom
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Originally Posted by Russ White View Post
Hey guys, this is all very interesting, but not really in the scope for this module.

It is not intended to be a DSP. You can interface with a DSP if you like.

It is quite simply a USB Audio Class 2 Device with PCM and SPDIF output.
Russ - you're right. Sorry, dude.

A high quality USB to SPDIF module would be well received.

Interestingly the XMOS guys are based a couple of miles from me...

Mark
 
Old 12th January 2011, 03:56 PM   #175
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Default If you

use a Mac, Pure Music can handle all of your digital cross over needs with very high precision, then output the signals to multiple TPA DACs. Doing the crossover in the computer seems to be a much simpler approach to me, with less hardware.
Although USB2 should handle multiple channels quite effectively, in the real world some people seem to be having problems getting USB2 to operate glitch free with just two channels of 24/192? I wonder how easy it will be to get 6 channels (for a three way xover) of 24/192 operating glitch free through a USB2/I2S interface, in the real world.
 
Old 12th January 2011, 05:32 PM   #176
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Originally Posted by barrows View Post
Doing the crossover in the computer seems to be a much simpler approach to me, with less hardware.
Although USB2 should handle multiple channels quite effectively, in the real world some people seem to be having problems getting USB2 to operate glitch free with just two channels of 24/192? I wonder how easy it will be to get 6 channels (for a three way xover) of 24/192 operating glitch free through a USB2/I2S interface, in the real world.
Greetings Barrows,

I'm running crossover/delay software for 8 channels as well, but on a PC. If I wanted to switch that interface hardware over to my Mac Pro as a source, I would have more and different driver, routing and software issues. I inquired here about running filters in XMOS hoping for a greater measure of 'plug-and-play'. I didn't realize that regardless of the number of cores, the XMOS chips seem to have only 16 1-bit ports (if I'm reading the table correctly).

From reading Russ's posts for a number of years now, I believe that he shares enthusiasm for an external crossover solution, right? It's more a matter of how many problems to tackle at once. Eight channel, plug-and-play USB -> every imaginable format would surely be sweet, but the XMOS is going to enforce limited choices. I personally prefer I2S I/O.

Let us know over in the other thread how that tweaked legato sounds after you fire it up, OK?

Cheers,

Frank
 
Old 12th January 2011, 06:26 PM   #177
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I would think using DSP for crossover, processing etc. would be about the best way to do it with low latency, low CPU usage. I think Metric Halo does it with Sharc DSP.
 
Old 12th January 2011, 08:23 PM   #178
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Originally Posted by regiregi22 View Post
Going balance only doubles this problem
Another solution, if you can set up the micro controller, is to use the PGA series of chips from TI. These should have incredibly good tracking.

Quote:
Originally Posted by fb View Post

If the SMD soldering were magically done it's not hard to imagine a cheap and easy digital only DSP board booting from E2PROM, and the firmware done in Sigmastudio via AD's USB dongle.
This is what I'm aiming for. I've managed to make and solder my own PCBs with lead spacing the same as the Sigma chips before, although this was with a 10 pin CS2000.

I've been experimenting with solder paste, as used in wave/reflow soldering and putting the PCBs in the oven. This was for soldering high power LEDs which do NOT like high temperatures at all. The oven method lets you heat everything up slowly and stops you exceeding the bust temperature of the LEDs.

The paste contains a lot of flux so the volume of the paste shrinks considerably when it melts. Now the solder likes to adhere to metal things rather then the FR4 epoxy, preventing legs from being soldered together. This worked wonderfully when soldering Cree XP-G LEDs, so I'm hoping I can use a similar thing with the AD chips. If not it's out with the 0.2mm soldering iron cartridge and solder wick

Using an outboard DSP chip wins hands down over the PC, simply because this places no constraints on the sound configuration of the PC. It keeps everything separate, allowing you total freedom with whatever you do on the PC.

My PC isn't a music only machine, I need it to be able to play games/stream videos via web browsers, play movies and record (why I want a 2 channel I2S input with the Xmos )/playback. All software based DSP stuff that I've seen, appear to come with severe limitations when it comes to using all sorts of other programs.
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Old 17th January 2011, 03:31 PM   #179
WDYSUN is offline WDYSUN  Italy
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Quote:
Originally Posted by LeonvB View Post
Actually I would prefer an off-board connector, so the user can select their prefered mounting type/method and no board would need to be replaced when the USB port is damaged. Also mounting it into a case gets much easier as you could simply drill a round hole for fi. a Neutrik USB connector.
I strongly agree with this... I have a dac kit from china with onboard usb and it was such a pain to cut an acceptable hole on the chassis.

Russ I hope you are doing the board this way!

Pietro
 
Old 17th January 2011, 03:39 PM   #180
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Default Sorry guys...

Quote:
Originally Posted by WDYSUN View Post
I strongly agree with this... I have a dac kit from china with onboard usb and it was such a pain to cut an acceptable hole on the chassis.

Russ I hope you are doing the board this way!

Pietro
My 2 cents: I strongly disagree. I would much prefer a board mounted USB connector. Having to DIY a very high speed (USB2) cable harness to a separately mounted jack just seems like a great way to have signal degradation. With a board mounted jack, Russ can play close attention to impedance of the traces, and get everything right. Considering how sensitive even async USB is to cable selection, I do not want to risk introducing problems via flying wiring from board to connector. Remember, USB2 data transmission is a very speed signal.
 

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