DSP Xover project (part 2)

[chaparK]

Originally Posted by dahlberg

Ok, I'm reading up on spdif versus I2S elsewhere so lets drop that for now

Basically, SPDIF is plug and play meanwhile I2S is not.

SPDIF (Sony Philips Digital Interface) is a single signal that carries audio data and some metadata, with the clock embedded in the signal using biphase mark coding. This coding strategy allows extracting the clock and the data separately from the stream.

On the other hand, I2S (Inter IC Sound) is a protocol for conveying audio data between chips. I don't think it was ever intended for use by the final user, but only for electronic engineers designing the board. It consists mostly in 3 signals: the data, the bit clock that's useful for sampling the latter data stream, and the Left/Right clock useful for deciding if the bits being sampled belong to the left of the right channel.

On the SPDIF side, all the communication aspects have been normalized: the signal amplitude, the line impedance, and there's theoretically enough metadata in order to properly decode the data stream.

On the other hand for I2S, it's all up to the designer. Voltage levels are not normalized (it can be 3.3V, 5V or whatever, TTL or CMOS). Then the receiver must know how the bits are aligned in the stream, how many clocks per frame (referred to fs clock) etc. This makes that if you plan to transfer audio with I2S, you must know exactly what the transmitter is able to spit out, then setup the receiver accordingly (and sometimes insert logic level translation between the receiver and the transmitter).

Nice to hear that the programming is coming along, are you expecting us to
participate in some way ? Maybe ideas for neat functions ? For instance, I
could go for a variable slope function for the shelving filters instead of the
usual fixed 6 or 12db's. From 3 to 12db maybe.

Yes there's a lot of stuff going on lately. Mostly programming, but I'm also on the way to finish hardware debugging. Now regarding suggestions for more features, I must say I already have a huge list of processing routines that I need to implement and I'm not going to add anything on it before the first release in October - otherwise it's going to push back the initial release. After the first release I'll be more than happy to take good note of every one's needs.

[dahlberg]

Ok, I got my questions answered Will there be any pre-presentation of hard and software before the actual release ?

[chaparK]

Originally Posted by dahlberg

Will there be any pre-presentation of hard and software before the actual release ?

I'll do my best to make information available as the various components (hardware, firmwares and software) are getting close enough to their final form for the release.

This week I've set up the digital input and the sample rate converter. It's all going smoothly and the project is on track.

One more feature I haven't mentioned so far: There's also onboard an isolated command for external relays intended for turning on and off your amps.

[alugner]

To me this project looks very sane. I was considering a Behringer, but they seem not really suited for domestic use. One benefit of theirs is the possibillity to use a microphone for automatic response correction. On the other hand they are not DIY, which is half of the fun.

[dahlberg]

Lets say I'm going for the digital solution, analog + digital + I2s input / spdif out.
Is there still need for the +/-12v supply then ?

[dahlberg]

About the 5v supply. How much current will be sufficient ?

[chaparK]

Originally Posted by dahlberg

Lets say I'm going for the digital solution, analog + digital + I2s input / spdif out.
Is there still need for the +/-12v supply then ?

Ok. The 5V supply is only used to power digital sections. Some chips use this 5VD as supplied, others require 3.3V and/or 1.2V. The latter are derived from 5VD with onboard regulators.

There's a separate 5VA (analogue). It's derived from the +12V supply. That's why you must always provide +/-12V.

If you plan to use an analogue volume chip, CS3318 needs +/- 8 to 9V and CS3308 needs +/- 5V. These 2 supplies are again derived from +/-12V with onboard regulators.

Originally Posted by dahlberg

About the 5v supply. How much current will be sufficient ?

1A is safe. Power lines are also available on the expansion ports so you can draw current here for your devices attached.

[chaparK]

Hi gents!

I have now approximate pricing information for the DSP board including software. To be confirmed!

- between USD 260 and USD 290 for the board without analogue volume.
- between USD 280 and USD 330 for the board with analogue volume (CS3318).

Shipping comes on top in all cases. For UE buyers, add 15% VAT.

I'll order a production run soon so that I can start delivering in October if there's no major shortage of chips.

I need to have a feel of what proportion of boards should get the analogue volume chip mounted on it, so I'd like to ask you whether you would prefer a board with the CS3318, or without that chip in order to save about USD 40. (If there's no analogue volume chip, the DACs are in charge of the volume control in digital domain - so there's still volume control, no worries).

This is not an order request or whatever, it's just for me to have a feel of how many CS3318 I should buy. So unless you don't need a DSP board at all, don't be shy to give your input. It's a kind of poll - I'm not going to contact anyone who's taking part.

My initial guess is fifty-fifty.

[alugner]

All right, I enlist for a board with the CS3318. I'm quite new to posting here but I've followed this thread with interest. Exciting!

[dahlberg]

I'll take a complete board Have you decided on what op-amps to use ?
If I'm using opamps at all I kind of like the "LT 1361".