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Old 14th December 2012, 01:00 PM   #3411
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Quote:
Originally Posted by opc View Post
Does anyone have any information on exactly what IC19 does? It's a Quick Logic QL3004 but I can't seem to find any data on it.

It looks like either a level translator or some sort of re-clocking or switch interface.
QL3004 is a strange FPGA device (unless all FPGA's share the same I/O level flexibility). It's datasheet tells:

Advanced I/O Capabilities
ē Interfaces with both 3.3 V and 5.0 V devices
ē PCI compliant with 3.3 V and 5.0 V buses
for -1/-2/-3/-4 speed grades

It's got actually two supply inputs: Vcc which is Supply Voltage, min=3.0V, max=3.6V. So this is also 3.3V (nom) device. However, it's got another supply called Vccio meaning "I/O input tolerance voltage" which can vary from 3.0 to 5.25V in "commercial grade" devices. So it has some special logic I/O ports which might be programmable for different I/O voltages or just have such parameters for Vih, Vil, Voh (whatever are applicable) that the different I/O levels just work with the device with the set Vccio.
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Old 14th December 2012, 01:01 PM   #3412
qusp is offline qusp  Australia
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so its a level shifter?

oettle: ahh I didnt read all the way down, yeah thats quite some jitter party haha

Last edited by qusp; 14th December 2012 at 01:06 PM.
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Old 14th December 2012, 03:13 PM   #3413
oettle is offline oettle  Germany
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Originally Posted by opc View Post
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.
Here the list of mods again. The red ones are the more important ones.

qusp: I lived for about a year in Sydney. Very friendly and helpful people there. Small little world, isn't it.
I made the experience that understanding of basics isn't a disadvantage.
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Old 14th December 2012, 03:30 PM   #3414
qusp is offline qusp  Australia
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by level shifter, maybe i've used some incorrect terminology, logic circuitry is not my thing, I mean shifting voltage compliance for the i2s to allow communication between 3v3 based and 5v based chips.

as for the rest....what? haha i'm at a loss to pull the basics from the pile of condescension. the DCX is a trainwreck before and after the mods compared to what can be done IMO, you made some improvement, which you should be congratulated for, so I did. more in the jitter than the rest, but 3db improvement overall is still significantly less than 16bit performance, no need for subtlety there.

i'm sure it can still be used as part of a good system, but no way would I expend the effort some are going to with the options that are currently available

first time i've ever heard the people of Sydney called friendly =) (Aussie in joke)

anyway i'll leave you guys to turn water into wine, godspeed!

Last edited by qusp; 14th December 2012 at 03:53 PM.
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Old 14th December 2012, 03:55 PM   #3415
oettle is offline oettle  Germany
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I'm using 3 of these trainwrecks and Iím pretty happy with them. To my experience there is nothing wrong with the DSP, the ADC and DACs. The rest can be modded. So you end up with a price which is about twice the original price of the DCX which is still very cheap. There are much more expensive solutions out there which are not necessarily better.
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Old 15th December 2012, 04:09 PM   #3416
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I picked up some cheap ebay dac kits (one built, one truly a kit) and they are setup with the behringer now in some really deluxe mounting

for diy guys, having spdif out really is a fun thing to have. I can try these dacs for a bit, hack on them, maybe try something else later if I want.

(these are dual-mono wm8741 with wm8805 receivers, all underneath the white boards).

I will do a measurement of these, later on, but sonically they blow the onboard analog-out system (including its stock psu) away.

the dual mono config of these ebay dacs is also kind of a fun detail, to me. each dac chip now handles its own speaker. left/tweeter gets its wm8741 chip, right/tweeter gets its own. no one has to share

the wolfson chips have a 2db cut feature so you can't overdrive them when 'near 0db' levels come in (which happens hourly on many internet radio stations that I listen to). I don't miss 2db, but I do hate harsh clipping (a lot of cheaper modern dac chips do NOT handle gibbs issues well).

its also really nice that I no longer have to deal with the ultra hot 22db signals that come from the behringer analog-outs. those were really too strong for the cirrus vol control chip I use and I hated having to atten so much just to interface with them.
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Old 15th December 2012, 06:59 PM   #3417
oettle is offline oettle  Germany
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Added the Jahonen mod to the list of know mods.
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Old 15th December 2012, 08:26 PM   #3418
oettle is offline oettle  Germany
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Well done liuxworks. Congratulations!

I think your solution is a good approach to replace long analog cabling between DACs and power amps. Also the onboard clock oscillator might have a bit better jitter values than the poor DCX crystal circuitry.
For short cabling it is worth to think about passive analog outputs or Janís active outputs and about a low jitter clock instead.

Keep on modding - itís fun!
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Old 15th December 2012, 08:49 PM   #3419
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but with the 'dac-sink' (half dac, half heatsink, lol!) sitting on the floor, I've swapped long dcx analog cables for long dac analog cables. heh.

I still think the cirrus transmitters would be easier to use since they don't need any local crystals. otoh, if removing the tanks from the wolfson still lets it work, then it would be an even draw between them.

the 8420 will have to be looked at next, I guess. everyone complains about it, so perhaps it does have to go
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Old 15th December 2012, 09:06 PM   #3420
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Thinking about the total power dissipation isn't such a bad idea.
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