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#315002 - 07/16/10 01:40 AM Re: PCB Fabrication [Re: ClubNeon]
CV Offline
Founder, Axiom Upgrade Club
shareholder in the making

Registered: 07/20/06
Posts: 11235
Loc: Richland, WA, USA
I would definitely try one of those. After I have the money. Which would be after the Axiom 30th year anniversary celebration.

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#315144 - 07/17/10 01:08 AM Re: PCB Fabrication [Re: CV]
CV Offline
Founder, Axiom Upgrade Club
shareholder in the making

Registered: 07/20/06
Posts: 11235
Loc: Richland, WA, USA
And now after making sure the basement finally gets done and I have Hesta Prynn DJ my Basement Grand Opening.

I look forward to hearing more about this project.

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#315151 - 07/17/10 03:30 AM Re: PCB Fabrication [Re: CV]
ClubNeon Offline
connoisseur

Registered: 02/06/09
Posts: 3448
Loc: Western Maryland, USA
I realized I said "receiver" in my last post, but this is obviously a pre-amp/processor, with the XLR outs, and no internal power amps.

Speaking of power amps, that was a previous project which I never finished, because the PCM to PWM controlled amp chips I wanted to base it around materialized too late, and then with much lower specs than promised. But anyway, I was used to the power supply design for large devices. Where every Watt counts, and heat is can become a serious problem.

I started looking at power supply designs for the digital and analog stages in this device today. Even something as inefficient (but with very clean output) as a shunt regulated PS is feasible.

I'm narrowing down options now. But it looks like for the digital stage, I'll be using a transformer which can output 9 Volts from 115/230 AC, and then regulating that down to 5 Volts into the digital board. From there I'll be using very fine regulators to get the 3.3 and 1.2 Volt feeds where needed. The analog devices (basically just the DAC output, and opamps feeding the XLR jacks), will need a bipolar (+/-) PS ending up with just under 4 Volts. That has to be the absolutely cleanest power.

The system will be comprised of several boards. The DAC board I've talked about. Also the HDMI input board, which will connect to the motherboard, or DSP board mounted on the bottom of the chassis. The DSP board will connect over to the UI board which will provided the front panel controls. The DSP also outputs to the aforementioned DAC. The PS boards and transformers will be to the left and right of the DSP board (near the air vents in the sides of the case).

The DAC board will have 2 rows of 8 XLR jacks. I'm using vertical mount models, which would normally be facing up off the board. But instead the board will be vertical, parallel with the rear of the case. The XLR jacks themselves will be fastened to the back panel, so the solder joins will not be stressed on plugging or unplugging the cords.

The HDMI board will be above the DAC board. There'll be 5 HDMI ports, and 1 output. Similarly to how the XLR jacks were the mounting point of the DAC board, the HDMI jacks will be screwed to the back panel.

So I have basic ideas about the HDMI board, and only rough guess how the DSP board will go. The UI is still up in the air. Won't need too much, volume knob, menu/arrow/enter keys, input selector, and a display. I've not decided about an on screen display yet. That depends on how hard it is to encode into an HDMI compatible interface and format.
_________________________
Pioneer VSX-1018AH-K, PDP-5020FD, DV-79AVi
Axiom M22s, VP150, QS8s
Sony PS3, surround backs
-Chris

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#315152 - 07/17/10 03:52 AM Re: PCB Fabrication [Re: ClubNeon]
CV Offline
Founder, Axiom Upgrade Club
shareholder in the making

Registered: 07/20/06
Posts: 11235
Loc: Richland, WA, USA
Yeah, I'm interested in this, but I'm also wondering how much I'd miss the other features in a pre-pro that aren't part of this design. But even if I don't use it as my actual main pre-pro, I'm still interested in getting one to compare and see how it works.

I'm still not sure on the assigning of the channel outputs, so maybe you could go into more detail on that. Also, how will calibration work? I'm assuming some basic adjustments will be included, right?

Also, I'm thinking for my personal uses I'd be more comfortable with 6 or 7 HDMI inputs, but 5 would work for now.

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#315159 - 07/17/10 05:28 AM Re: PCB Fabrication [Re: CV]
ClubNeon Offline
connoisseur

Registered: 02/06/09
Posts: 3448
Loc: Western Maryland, USA
5 HDMI ins/1 out, is the biggest chip I can get right now. But it isn't even as flexible as the 4-in chip. I've not done much looking at the HDMI board yet. But I am considering the 4-in chip paired with a separate 1-out chip. But what I could do is use two 4-ins together, for 8 total.

I'm building this as a platform (actually, the way I've designed the DAC board, I could easily substitute in a cheaper un-balanced RCA, based design with 8 stereo DACs, or even two 8-channel DACs). I'm not ruling out features, just not going to bother licensing them at first. But the DSP chips I'll be using have enough power to decode Dolby/DTS lossless up to 96 kHz (at least), and run either Audyssey or Trinnov processing. I'm still looking at how to get a mic hooked up. But that's an analog in, and makes things more difficult. I could also possibly support HDMI Audio Return Channel, it's in the chips, just needs to be assigned to an input (but it could possibly have AC3 audio, which needs a license).

It'll definitely have distance delay compensation. There's 256 kB of ring buffer space per DSP. That's allows up 42.667 ms of delay for 8 channels (each DSP will be handling 8 channels). Multiply 42.667 ms by the speed of sound, and that allows for speakers to be up to maximum difference of 47.6 feet.

Individual channels trims, adjustable in 0.5 dB steps. The master volume can also use 0.5 dB steps. The neat thing is, it's even smoother than that. When you go up or down a half dB, the volume ramps in 32, 1/64th of a dB steps. Even cooler, that's not even linear, it uses a logarithmic acceleration curve to reach the requested volume. It (un)mutes the same way.

Also multi-tap FIR filters for crossovers. That allows for phase aligned, highly customizable settings. I'll be doing the crossover work in the main CPU, and handing the resulting channels to the two DSP chips. Well, that's my initial plan. Still need to figure out what chips, and how many.

That brings me to your first question. HDMI carries at most 8 channels of PCM audio. Most of the time these are configured as 7.1, but the .1 isn't true, it's a full frequency range channel. That doesn't matter for this discussion. Just know the player is decoding what ever is on the disc to PCM and outputting how ever many channels result.

Those channels hit the first chip. This is where I'd be running Dolby's, DTS's, Audyssey, Trinnov or my custom processing to create additional channels from the existing. It can look at everything about those raw channels, and manipulate them in different ways. Say your disc has a 5.1 track, but you've got a 7.3 setup. So the processor looks at the surround channel, and creates rears from that. Then it moves onto the bass processing. You have two subs in the front of the room and one in the rear. You want all the subs to get the LFE channel from the disc, so it's mixed into all three, but you want stereo bass for the front of the room, so the crossover of the center is mixed into both front subs, but only the crossover of the left main goes into the left sub, and right to the right. The bass signal from all 4 surround channels is taken into the rear sub.

That gives you a total of 10 output channels. The first DSP handles channels 1 to 8, the second 9 to 16. These might be assigned as:
1. Left
2. Right
3. Center
4. Left Surround
5. Right Surround
6. Left Rear
7. Right Rear
8. Left-Front Sub
9. Right-Front Sub
10. Rear-Sub
But there's nothing fixed about those assignments. You can plug into any jack and send that signal to any speaker. (The Trinnov code actually has discovery routines to try to figure out where the speakers are in the room, and auto-route the channels.)

The order of processing in the first CPU is:
Channel creation (from existing signals, dematrixing, or sinks which will receive crossover information or mixes).
Crossover processing, remove the low-cut info, and prepare it for mixing.
Mixing, combine signals from other locations into the final assignments.
Send the channels to their proper DSPs.

The DSPs don't seem to do much right now. They're just handling the delay alignment. But they'll also run any room correction processing, EQing, standing wave attenuation, etc.
_________________________
Pioneer VSX-1018AH-K, PDP-5020FD, DV-79AVi
Axiom M22s, VP150, QS8s
Sony PS3, surround backs
-Chris

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#315160 - 07/17/10 05:35 AM Re: PCB Fabrication [Re: ClubNeon]
CV Offline
Founder, Axiom Upgrade Club
shareholder in the making

Registered: 07/20/06
Posts: 11235
Loc: Richland, WA, USA
Great stuff, Chris. This could be your calling.

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#315184 - 07/17/10 02:05 PM Re: PCB Fabrication [Re: CV]
ClubNeon Offline
connoisseur

Registered: 02/06/09
Posts: 3448
Loc: Western Maryland, USA
This is not far from what I already do at my job. It's selecting hardware and software, combining them together in such a way that it solves the problem at hand. The pieces are a little smaller, but they still have well defined ways of interacting. That is what surprised me. How well defined the functions and sample implementations of these really complex chips are these days.
_________________________
Pioneer VSX-1018AH-K, PDP-5020FD, DV-79AVi
Axiom M22s, VP150, QS8s
Sony PS3, surround backs
-Chris

Top
#315199 - 07/17/10 02:54 PM Re: PCB Fabrication [Re: ClubNeon]
CV Offline
Founder, Axiom Upgrade Club
shareholder in the making

Registered: 07/20/06
Posts: 11235
Loc: Richland, WA, USA
As far as licensing goes, how hard and expensive would it be to implement something like DLNA? Will this platform allow for firmware updates?

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#315203 - 07/17/10 03:24 PM Re: PCB Fabrication [Re: CV]
ClubNeon Offline
connoisseur

Registered: 02/06/09
Posts: 3448
Loc: Western Maryland, USA
Firmware upgrades, absolutely. They're essential to any modern piece of equipment. The main CPU has both USB and Ethernet interfaces.

As for DLNA, I don't know where I'd do the A/V decoding. The CPUs in the platform are pretty much accounted for, I'd have to add another chip just to handle that. Plus, it feels like something better accomplished by a device designed for the task.

Don't worry about the lack of HDMI inputs. This pre/pro will allow multiple preset states. So it won't assume there's only one possible device behind each port. I had initially planned to only have one input, and require the use of an external switch. But every HDMI input chip already has a hub built into it these days. Still the idea stands, that it'll be easy to switch all available input configuration settings with the push of one button.
_________________________
Pioneer VSX-1018AH-K, PDP-5020FD, DV-79AVi
Axiom M22s, VP150, QS8s
Sony PS3, surround backs
-Chris

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#315207 - 07/17/10 03:32 PM Re: PCB Fabrication [Re: ClubNeon]
CV Offline
Founder, Axiom Upgrade Club
shareholder in the making

Registered: 07/20/06
Posts: 11235
Loc: Richland, WA, USA
Originally Posted By: ClubNeon
Firmware upgrades, absolutely. They're essential to any modern piece of equipment. The main CPU has both USB and Ethernet interfaces.


Very cool.

Originally Posted By: ClubNeon
As for DLNA, I don't know where I'd do the A/V decoding. The CPUs in the platform are pretty much accounted for, I'd have to add another chip just to handle that. Plus, it feels like something better accomplished by a device designed for the task.


I thought about it after I asked it and came to the same conclusion. I figured it wouldn't be something you'd care to concern yourself when anyone could just get a player of some kind that already has it. Still, some of your ambitions regarding this project have surprised me.

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