Apox digital X-over

[harvardian]

Hi,

I am looking into creating an audiophile digital crossover. As co-developer of the APOX volume control, I think there may be merit in a unit designed for best audio performance.

Instead of just allowing Nth order slopes, I am hoping to allow arbitrary mag/phase plots to be downloaded and the appropriate filter coefficients calculated. Of course, standard butterworth and other types would be supported.

I am not sure that a DSP is really needed for the calculations. I would rather use a couple of high speed microcontrollers or even a low end X86 type chip (built in FPU).

Could people list a few high level specs that they would like to be included...

In general, I was anticipating:

SPDIF or I2S inputs
Analog Inputs: 24/96 ADC
six or eight channels 24/96 DAC (3 or 4 way)
Digital output?
Volume control via PGA43XX or PGA23XX in analog domain

Etc...

Dale

[jleaman]

Great idea. Got any sujestons and planns..

j'

[jwb]

You'll be a lot happier with a SHARC than with some x86 CPU. The performance per unit heat produced will be much much higher, and the pin count will be lower.

I've been playing with digital x-overs in software, and I'd like to see phase, slope, 3dB frequency, and passband attenuation all controlled in software.

I guess it really depends on how far toward the high end you want to go. Each channel could have digital outputs, single-ended and balanced analog outputs, etc. The main concern quickly becomes having enough room for all the connectors

[pinkmouse]

Great idea Dale

Ok, my suggestions-

Good to have

2 ins, and 3+ sub, or 4 +sub outs.

Option of balanced or unbalanced inputs and outputs

Programable/controlable via Usb and a Unix program, as users of both Macs and Pcs can get Linux/Unix running on their machines.

Adjustable delay for time alignment of drivers.

If possible

Linkwitz transform or other EQ on the sub or bass outputs

Maybe two or three bands of adjustable eq for room correction

Volume controls optional for those that don't need them.

[roddyama]

Hi Dale,

Now you’re talkin’! I’ll think about this some more, but here are my first thoughts.

Digital time delay per channel
An extra channel per channel for notch filters, or baffle step comp., or FR tailoring.
Channel by-pass
Level per channel
System configuration memory and/or programmable pre-sets

Rodd Yamashita

[slowmotion]

Hi Dale ,

I would be interested too

8 analog outputs would be nice

cheers

[pinkmouse]

Rodd

Channel mutes perhaps, channel bypass could lead to blown tweeters

I think level per channel might be easier to handle in the analogue domain rather than digital, to save processing power, but hey, what do I know

At least two presets is definitely a good idea, then you could have one for music and one for HT for instance.

More general thoughts-

A pink noise generator for system setup would be handy...

[roddyama]

Originally posted by pinkmouse
Rodd

Channel mutes perhaps, channel bypass could lead to blown tweeters

Hi Al,

Yeah, I guess I could wire straight through channels externally. I thought about that because my Heathkit xover has a by-pass, but it is for the bass range only, so in general, you're probably right.

Rodd Yamashita

[jleaman]

Is this going to be balanced or non-balanced.
Will it be adjustable.?


will there be one main in and 4 or so out's..

My idea.

Main in
Sub out
hi out
mid out
low out

All adjustable..
Desplay ? yes no.?

[pinkmouse]

Another quick thought, a fixed high Q high pass filter at say 10Hz, for those of us that still use vinyl would be nice