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Old 14th December 2012, 01:32 AM   #3401
qusp is offline qusp  Australia
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Quote:
I considered that...
knowing you i'm sure you did... but I wanted to know what made you decide against it, since i'm aware of a couple of projects you've got going that would seem to fit quite well with just starting from scratch and then using something like allocator, or leverage the Sandybridge chipset (Intel i3, i5, i7 etc) you probably have somewhere already for something like this

I just happen to think that software or DSP accelerated software is much more powerful these days than the aging DCX. the case.... well we both have a problem there so i'm not saying anything

for tying into the sharc, maybe you could use a low ohm (20-47ohms) or perhaps even zero ohm SMD resistor network soldered right on the edge of a PCB which has your interfacing stuff on and then use solderpaste and hot air to mount that vertically. thats about the neatest way I can think of. of course it would need to be supported.

Last edited by qusp; 14th December 2012 at 01:38 AM.
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Old 14th December 2012, 02:09 AM   #3402
opc is offline opc  Canada
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While we're on the topic of mediocre performance, I've attached all my "baseline" measurements below. This is a bone-stock DCX2496 measured on an APx585.

Pretty much everything is buried in there somewhere. I didn't do THD vs. Frequency but I'll run those a little later before I modify anything.

I'm going to start by tearing out the entire SMPS module and replacing it with a fully linear supply using a separate PCB mount Amveco toroid for the digital and analog sections. I'll be using TI's TPS7A4700/3301 ultra low noise regulators pretty much everywhere. I'll make a pair of little break-off PCB's to replace the two on-board linear 5VA regs, and replace the 3.3VA reg with the same sort of thing but soldering that might be a little more tricky since it's derived from an SMD transistor.

I expect the above to clean up the noise floor by a large margin, along with moving the AES/EBU input away from the analog signals and direct wiring it to the isolation transformer.

I'll report back with progress.

Cheers,
Owen
Attached Images
File Type: png FFT Spectrum Monitor - midrange.png (131.0 KB, 306 views)
File Type: png FFT Spectrum Monitor - no XO.png (170.6 KB, 299 views)
File Type: png FFT Spectrum Monitor - tweeter.png (127.7 KB, 296 views)
File Type: png FFT Spectrum Monitor - woofer.png (131.6 KB, 288 views)
File Type: png FFT Spectrum Monitor - zoom in no xo.png (239.2 KB, 287 views)
File Type: png FFT Spectrum Monitor digital input - idle.png (141.4 KB, 43 views)
File Type: png FR - 6 channels 200Hz 1500Hz (zoom).png (147.2 KB, 39 views)
File Type: png FR - 6 channels 200Hz 1500Hz.png (257.7 KB, 45 views)
File Type: png FR - 6 channels no XO.png (165.9 KB, 46 views)
File Type: png Signal to Noise Ratio (2VRMS).png (55.4 KB, 52 views)
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Old 14th December 2012, 02:10 AM   #3403
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It may be that something like the soon to be released miniSharc from minidsp might do what you're after Owen ... miniDSP - December 2012 Newsletter | miniDSP
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Old 14th December 2012, 02:15 AM   #3404
opc is offline opc  Canada
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Originally Posted by hochopeper View Post
It may be that something like the soon to be released miniSharc from minidsp might do what you're after Owen ... miniDSP - December 2012 Newsletter | miniDSP
Wow! That's pretty much exactly what I would like to start with. It looks like someone already did all the work that I have no idea how to do

hmm... definitely something to think about. I'll wait for it to release and see how the SW interface looks.

Thanks for the link!

and... a few more measurements as I hit the limit on the last post.
Attached Images
File Type: png Signal to Noise Ratio (9.1VRMS).png (53.9 KB, 57 views)
File Type: png THD+N Ratio - 2VRMS.png (50.2 KB, 49 views)
File Type: png THD+N Ratio - 9.1VRMS.png (50.5 KB, 42 views)
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Old 14th December 2012, 03:00 AM   #3405
qusp is offline qusp  Australia
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opc, i'm not sure ordinary quite covers it....

hochopeper thanks also for the link, looks like they finally removed enough stuff I dont want lol. the last version still had just a bit too much I didnt need and not enough power. I do wish they didnt force 96x sampling for everything...
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Old 14th December 2012, 05:33 AM   #3406
oettle is offline oettle  Germany
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Might be these measurements are helpful for you:
Ergo Audio :: Stock vs. modded
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Old 14th December 2012, 06:59 AM   #3407
qusp is offline qusp  Australia
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unfortunately IMO they reinforce my point more than anything....

opc with his renowned analogue design chops and with the DSP and software side taken care of for him, if he can be arsed, stands to end up with a significantly better unit by going his own way.

afaik hes working with the ESS ES9102 ADC as well

nice job on the mods though! they really are pretty well thought out and well executed.
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Old 14th December 2012, 07:20 AM   #3408
tomtom is offline tomtom  Slovakia
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Originally Posted by opc View Post
I might try it with my Amanero USB-I2S board this evening on the input side... that would allow a nice USB connection directly on the back of the DCX-2496 for digital input, which runs directly into the SHARC. No need for on-board ASRC, clocks, etc...
Please let as know! Im very interested. Actually im quite surprise that people who are making new digital input - didn't solved one very important thing. To get rid of ASRC. This is possible only via asynchronous USB or via slaving source to DCX dac clock /in fact not that difficult with sound card as Esi juli that can be slaved/ Im all for USB input to DCX! Maybe we can ask Amanero to write special version drivers with only 24/96 Khz enabled just to be on safe side. /in win7 you can force system to resample everything to desired FS/ Maybe this is worth of new thread.
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Old 14th December 2012, 12:15 PM   #3409
opc is offline opc  Canada
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Originally Posted by oettle View Post
Might be these measurements are helpful for you:
Ergo Audio :: Stock vs. modded
Holy Jitter Batman!

That last measurement is unbelievable... Perhaps that helps explain why the stock unit gets on my nerves so badly.

I'll repeat a jitter test on mine as well before making any changes.

This is part of the reason I'm worried about IC19. If it's responsible for that level of jitter, then I get the feeling it's easier to just start from scratch with something like the miniDSP SHARC.

oettle:

What exact changes would you say were responsible for the reduction in jitter? You have improved it by a large margin, but I would still say that it could use further improvement.

From your listening, was the jitter reduction a significant improvement sound-wise? I'm not of the mind that every ps of jitter is audible, but when jitter artefacts clearly extend up into the audible range as they appear to in your last measurement, I would expect them to be audible.

Also, it appears from our measurements that the old PS was quieter than the new PS. Our stock measurements vary by quite a bit.

Cheers,
Owen
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Old 14th December 2012, 12:30 PM   #3410
tomtom is offline tomtom  Slovakia
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This is part of the reason I'm worried about IC19. Owen
you dont need to worry, In any reasonable mod you feed clock from crystal DIRECT to DAC so you bypass anything between. Of course the same clock is feed to DSP too.

Last edited by tomtom; 14th December 2012 at 12:33 PM.
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