we've done experiments with intona and regen were usb isolation has proven to be far more effective than i2s isolation
which seems to suggest that most of the damage has occurred in the usb to i2s conversion by a sloppy usb signal
which doesn't seem to be fully cured by "audiophile" usb cards
Johns prototype isohub was pretty much a hit at the meet up here a few weeks ago
i think these type devices will be a must for usb dacs
There seem to be two issues that need addressing in USB signalling - common mode noise & signal quality
Common mode noise seems to be a much more common issue than previously credited when connecting USB devices to computers.
Removing this CM noise requires some sort of isolation that works prior to the USB receiver chip. In my experience isolation after the USB receiver is only partially effective. Isolation prior to USB receiver usually entails an isolator that works at USB high speed (480Mbps)
Any USB isolation I have experienced is also improved by having something that regenerates the USB signal with a certain quality & located close to the final USB receiver
If you had landed from Mars and were wondering about Computer Audio, would you immediately think that USB transmission from PC to DAC is just the ticket? I doubt it. So everything that the audiophile world are suggesting to improve the USB signal is surely a band-aid to make the best of an inadequate transmission solution? A bit harsh I accept and I agree that USB can sound pretty damn good. but .......
My understanding of Ethernet transmission is that it is good at common mode noise suppression and galvanically isolates the two ends of the chain. Surely that is a good basis to work on and better conceptually than USB?
Again apologies for interrupting this thread off topic. Won't do it again.
Maplin XM21X 12V float charging A123 26650 LiFePO4 battery/Maxwell Supercap PSU for Mitac PD10-BI J1900 Bay Trail, WTFPlay, Hiface Evo, Bow Technologies 1704 NOS DAC, StereoKnight TVC, Quad II monoblocks, ZU Audio Druid Mk4/Method Sub
nige2000 wrote:Yes would recommend doin the vref
Easiest step is three cells two for 3.3 and one for -3.3
Remove vref regs and 1.2v switch mode reg and replace with an ldo powered direct from cell
The other mods are much work
computer audio is deeply flawed
theres just far too much to fix
but it can be done with much expense on time and money
with various power supplies, clocks, usb cards isolators reclockers
Which is why I think using the ethernet streaming with the Oppo is interesting. I don't need to think about PC playback software and how they may impact the sound or
usb or any of that. I just select the music drive to be shared in Properties and let the Oppo UI take care of the rest. I would think this minimizes how much you need to mess
with PC optimizations. With the exception of the hard drive power. I plan on making a power supply for that. Should be simple.
To be vaguely back on topic - one of the lessons I've learned is that retail DACs are a package of hidden compromises, I can't imagine not sticking with diy from here on out...
wouldnt be at all surprised if other parts of the oppo would benefit from better power
think a lot of dacs are made by engineers with simulations and budgets
sd card player, modded soekris dac, class a lifepo4 amp or gb class a/b amp, diy open baffle speakers based on project audio mundorf trio 10's
So on the scale of Soekris mods where does supplying external power to the shift registers rank? And is a hot air gun recommended for removing the components?
I'm not going to comment on the shift reg power as I haven't done that to mine yet... but I would not use a heat gun to remove components on the DAMs around the shift regs. Too many nearby parts that could be unexpectedly be affected. I have had good results with 2 fine-tip soldering irons on mine and other boards like this.
The only exception to that is for removing the output stages. There I masked the surrounding areas with Kapton tape and used a fine-nozzle heat gun. That is what I'll use when I remove the switching regulator and the 3.3v regulator.
You could use a special type of solder mix which stays liquid for a much longer time than normal solder & allows multi-legged ICs to be lifted off their solder pads without much difficulty - essential for removing parts that are surrounded by other small part.
wushuliu wrote:So on the scale of Soekris mods where does supplying external power to the shift registers rank? And is a hot air gun recommended for removing the components?
would be first on the list of mods
hot air is great for getting the output buffer chips off, as two of them is heat sinked
actually maybe if the 5v regs are removed they can stay on to little or no detriment
but ive used the low temp solder either its great
a blob of ord leaded solder and tweezers would pull the 4v regs off no probs either
only thing with hot air is that need to be careful not to blow other parts off
which is unlikely except for the little resistors
sd card player, modded soekris dac, class a lifepo4 amp or gb class a/b amp, diy open baffle speakers based on project audio mundorf trio 10's
I made a very small nozzle to use with my garden variety MAKITA hot air gun and lots of KAPTON tape. Used a piece of copper foil - the stuff they make foil crossover coils with, to make my nozzle.
I used a soldering iron to clean up the pads and parts that did not quite blow off.
Be prepared to move the board around to get the best angle. Don't get in a hurry or get lazy.
Study the board and plan your removal process.
In my case it was simple since all I left on the shift register side of the board were the shift registers and the resistors.
Components on the left side of the board were removed with the soldering iron. For the large electrolytics I broke off the tops to get better access to the pads. All are removed.
I also used the heat gun to remove the +- 5 volts supplies.
i know development on this thread has mostly died (maybe all threads/forums) but i stumbled across some of these i got a while back to provide a differential clock signal for the dam
for those of us that think the stock adjustable clock is probably not a great idea
it should also allow for dual clk config with clk sel
i put one on a adapter board and it certainly does what it says on the tin looking at the scope
it seems to output two identical differential outputs
assuming i can use one for the fpga and the other + or - clk out for the 574 flipflop on inputs for pre-alignment
i will test it tomorrow
must be said the quality of these potato parts although expensive are top notch
this poor bugger survived a short (lifepo4 style) as did one of the 7474 chips in the past
sure beats the magic smoke!
nige2000 wrote:i know development on this thread has mostly died (maybe all threads/forums) but i stumbled across some of these i got a while back to provide a differential clock signal for the dam
for those of us that think the stock adjustable clock is probably not a great idea
it should also allow for dual clk config with clk sel
i put one on a adapter board and it certainly does what it says on the tin looking at the scope
it seems to output two identical differential outputs
assuming i can use one for the fpga and the other + or - clk out for the 574 flipflop on inputs for pre-alignment
i will test it tomorrow
must be said the quality of these potato parts although expensive are top notch
this poor bugger survived a short (lifepo4 style) as did one of the 7474 chips in the past
sure beats the magic smoke!
Damn them Ndk clocks
Ping it fly's from the tweezers
lost another one to the floor
Stole one of a USB to i2s and back in business
I've used a 22mhz clock as I had it working previous but on this configuration it looses lock intermittently
It is supposed to be 44/45 clks so I'll have to see if I've any of them
Sounds good despite
sd card player, modded soekris dac, class a lifepo4 amp or gb class a/b amp, diy open baffle speakers based on project audio mundorf trio 10's