Apox digital X-over

[harvardian]

Hi Petter,

Great suggestion. We did not know these exist. From 5-16 biquad filter stages.

1) Are the ones with built-in ADC/DAC good enough?
2) Should we use the all digital ones and use better ADC/DACS?

Dale

[scraggles]

Hi Guys,

I hate to disappoint, but we will not do any form of multi-channel decoding. There is too much competition and the development licenses are way too expensive…

Dale

Out of interest, what are you considering as competition for multi-channel decoding? Is there a DIY solution for this, whether in the form of a board that can be integrated or a total kit?

I'm contemplating building both a DAC and a Preamp, but see it being obsolete in no time. I could build multi-channel units, but how do I get the (DVD) signal into multi-channel?

[harvardian]

Hi Scraggles,

I guess that I was referring to all of the inexpensive HT preamps/receivers on the market. The licenses are geared towards shipping lots of units. Dolby Labs wants a bundle just to play.

There are no DIY solutions, and I fear that this is beyond most people, including me!


Dale

[dipchip]

What do people think about a system like this?

First there is a small PCB board: Call it BOARD A

BOARD A features:
(SPDIF and/or analog input)-> (I2S)->(differential output I2S (For long cable lengths) onto ethernet type cable)
a microcontroller to act as CAN Master node and have a USB PC interface.
The CAN bus is also placed on the ethernet cable.
There would probably be three RJ-45 jacks on this board. (one for each
speaker)


Then embedded inside each one of your speakers (maybe?) is BOARD B.

BOARD B: features
(differential input I2S )->(I2S)->(DSP digital filters with three
outputs)->(3 x 24 bit audio DAC outputs)->(volume controller)->(your power amp here)
There would be some sort of switch on the board where you would select L, R,or L+R (for example, even though the digital input would contain both L and R data.
The board could ignore the data it didn't need it for that particular speaker. or could mix L&R for bass managment etc..)
a microcontroller would act as a CAN Slave node and would send all received commands to the DSP.



BOARD A: could then receive all of the filter parameters via the USB bus.
BOARD A would then pass all of this filter parameters over the CAN bus
to the microcontroller on BOARD B, where they would be passed to the DSP
and to volume controller. That way you have digital going all the way to
your speaker.
The microcontroller would then store these parameters into EEPROM for later
use.

Does this seem like a good idea to anyone, or am I nuts!

Thanks,
Craig Beiferman

[pinkmouse]

Sounds good Craig, but do we really need another volume stage? It would only really be of any use if you just had one source, such as a cd player, and used the crossover as a pre as well. And you will also lose sales of the Apox kits!

Maybe you could also make the B board a basic 2 channel system, with extra add on boards each with another two channels worth of processing/DAC, for those with greater crossover needs. This might make it cheaper for those with lesser requirements, or the financially challenged

[harvardian]

The crossover is really geared towards DIY'ers that want to build "active" loudspeakers. For them, there would be a fully digital link from the source (CD) to the speaker. There will also be a ADC for those with analog inputs.

For this application, the volume control should be after the crossover in the analog domain.

We envision this system as just another choice in the APOX system. You could, of course, bypass the volume control on the crossover board and use one of the other APOX boards.

Of course, one could put all boards in a chassis and run amp outputs to the speakers. The break up of the boards lets the user choose either method.

Dale

[Peter Daniel]

You definitely need volume control in crossover modules to adjust volume for individual drivers. But the question remains if it should be as elaborate as APOX, or a simple trimpot which later can be replaced with fixed resistor would be enough? As you gear it towards DIY'ers, the latter could be cheaper and probably better sounding solution

[harvardian]

Hi Peter,

Here is our thought on the subject.

If you are actually doing an active speaker and would like the crossover/amps at the speaker, you would need to control the volume at the speaker. The crossover is acting like a preamp in this case.


Dale

[Peter Daniel]

This makes sense, but I guess you need a source switching unit in case you want more than one source.

[harvardian]

The APOX-IS1 should work

We may have a digital switching as well