Firestone BRAVO 24/96 USB transport w/o drivers + reclocker? - Page 28

BTW, I've received yet another USB isolation dongle today: http://www.olimex.com/dev/usb-iso.html

I think I've tried pretty much all the USB Isolation ADuM-based dongles available on the market now...seriously

The quality of the inbound USB signal is so important that I'm amazed by how primordial it actually is. This dongle might very well be the best sounding I've tried so far...need to run more tests.

Audio is a nasty hobby, because there's always something better sounding out there...hunt for it and buy it

Each upgrade renders the previous one laughable, of course. BTW, I was told that ADuM5000 is very nice but it has a very poor efficiency(28%) so it can get really hot, and it's an EMF feast as well. It seems rather clear that -as usual- a chip on its own is meaningless outside a proper circuit.

This dongle has a B connector on the computer side, gonna start looking for a snakey 4ft cable now.

did you get your aMG dongle yet? running it off what device?

The OLIMEX dongle also has power isolation...actually ADuM4160 took the market by storm because it's a cheap solution to USB data lines isolation, but what I was told about 5000 is "The ADuM5000 offers 5V Isolation in a small IC package, which is state of the art.  The tradeoff is that in order to isolate in such a small package, they require it to run at 180MHz, which is extremely high for a dc/dc and hence the noise and efficiency issues." Plus the 5000 datasheet talks about 75mV ripple, surely you can do much better than that if you don't require a small IC. As usual, the surrounding circuit matters more than the chips themselves...I've also only run my tests on the Tenor chip, they might differ on other chips...but I've got no use for 16/48 USB and the main affordable async transports either aren't compatible at all(Hiface) or have buggy drivers(Musiland).

ahhh, yeah the SQ has really gotten noticeably clearer w/ that new dongle...when will that stop.

this CD sounds like heaven: http://www.discogs.com/Autechre-Tri-Repetae/release/47276

Listening to those masterpiece albums that you've heard hundred times on a fully filtered Bravo is really an experience in its own right. Tri Repetae is the pinnacle of Autechre's sound in many ppl's opinions...hard to deny.

Autechre's sound really does benefit from a razor sharp and uber-tight transport

I will soon try a linear regulated 24VDC 1A PSU based on LM317T, eager to hear whether that'll make a diff. over the 0.5A Supplier PSU. The TREAD is also based on LM317T apparently.

Well, the only thing I know is that all the USB Isolation dongles I tried sounded different...not sure about the root reasons: PSU quality/filtering/ripple, EMF pollution(5000 being quite nasty on that point), USB signal purity/jitter, jitter eye diagrams.

Several manufacturers have told me that those chips are harder than it seems to properly implement, and all those figures in the datasheets were measured off an ADI board...so they will be much higher off a less researched design.

At some point, I did try a 4160-only dongle that made the sound worse...way worse. It was using this power isolation chip(150mV ripple): http://www.xppower.com/pdfs/SF_IL.pdf

My Corsair PSU was measured at <10mV ripple on its 5V rail...150mV is really off the charts

4160 on its own is not the warrant of anything for us...surely you will get data lines isolation, but feed it dirty power off a poor design and it will not sound "good". Prolly fine for industrial use, though...which is the primary intent of all those dongles.

PS: BTW, that's the power isolator used in the OLIMEX dongle: http://doc.chipfind.ru/pdf/itt/am1d0505s.pdf

"low ripple and noise" :)

Yeah, there are many schools in the DAC world: NOS, R2R, ASRC...the Sabre's have a built-in 192kHz ASRC that's here to lower jitter, but they're also said to sound "cold" and "clinical". Some of the most expensive Sabre based DAC's disable its internal ASRC.

The DacMagic is also said to sound awesome due to this very ASRC by its manufacturer, but many ppl claim it to sound no better than a $99 uDAC

The R2R ppl like to whine about the supposedly high noise of the D/S chips, but AKM said in their press release that even the 3 generations old AK4396 was able to reach the noise level of the R2R chips:

"This DAC is a large departure from other delta-sigma DACs designed by us and others like BurrBrown, Analog Devices and Cirrus Logic. The AK4396 is an entirely new modulator, pioneered and patented by AKM. It achieves something unique. In the past, many of the old Phillips and BurrBrown parts were R-2R* based products. These older products were looked upon as some of the best. One of the reasons was high frequency noise. In older R-2R parts, HF noise was not present. In all delta-sigma parts prior to the AK4396, everyone has fought HF noise caused from the delta-sigma modulator with the insertion of large filters and other parts to attempt to solve a problem created by the delta-sigma design. The AK4396 today effectively does not suffer any modulator-induced HF noise and is over 60dB better than the nearest Cirrus and BB devices. All of this HF noise can cause many audible artifacts downstream. That is the 'miracle' we believe is making the difference today. This part gives you the performance and linearity of a delta-sigma device with the noise performance of an R-2R part, something that was never previously available"

...as usual, ppl will never agree on those matters.

As far as I'm concerned, I really don't want my audio to go through a mandatory 192kHz upsampling.
 

Originally Posted by rehabitat 

Some new-ish impressions of the Bravo - http://www.stereo.net.au/forums/showthread.php/24469-Bad-transport-jitter-correction-good-transport?p=461048&viewfull=1#post461048

What's a PDX? The Bravo benefits greatly from a linear regulated PSU, and just as much from a USB Isolator. Surely, I wouldn't be so happy w/ it w/o USB Isolation and still using the cheapo SMPS wall wart.

When I first got the Bravo, I was too lazy to reconfigure the whole computer so I simply fit a Dayton glass toslink cable on its input and output a short coax to my Firestone Spitfire DAC = major improvement! The sound wasn't flabby anymore, and much tighter.

But it mostly boiled down to polishing a turd IMHO...the sound was clearly better, thanks to the great sounding WM8804 50ps reclocker, but going USB made up for another major step ahead. Toslink distorts the light signal, and POF is even worse than glass toslink...the light sources being crappy LED's. But yeah, the Bravo is a very good product IMHO...and it scales amazingly well w/ any improvement, whatever PSU/USB signal purity/cables length. I'm quite confident that this unit is not the bottleneck in my current set up, as any improvement done upstream or downstream always pays in cash. I'm eager to try that 24V LM317T based PSU

I sort of agree w/ the "Bad transport + jitter correction = good transport" statement in that thread, the Tenor chip is nice and all but I'm quite sure that I wouldn't like it so much w/o the WM8804 reclocking in the Bravo. When I hear what it does on a toslink>coax reclocking, I can more or less imagine how bad the Tenor chip would sound on its own. Surely, the Tenor chip in the Burson HA-160D doesn't sound as good as it does in the Bravo. Discrete reclocking is a god send, and that explains why several DAC manufacturers put WM8804 right before the DAC chip.

You can also read "Jitter is one thing, electro magnetic interference is another" in the first page of this thread, couln't agree more...isolation is the motto.

hard to answer...the coax input is highly dependent on the inbound transport.

from what I've gathered during my tests, the best results to be had from a computer source are by using the USB input(properly isolated) together w/ a short coax to your DAC....then you get the full benefit of the unit and truly unleash the WM8804 potential.

now to find myself a 4ft audiophool A/B USB cable on ebay

well, it's a dirty job but someone's gotta do it

The wireworld's are too pricey on ebay...OTOH, I can get this for pretty cheap locally: http://www.lacie.com/us/products/product.htm?pid=11179

but there's no audiophool talk like "triple shielded twisted pairs w/ hydrogenic dielectric shamanic insulation" blabla, so it might just be wasted money...plus the colors are ugly as sin. OTOH, if the wires don't touch each other, these might sound very good

I'm comparing the aMG and OLIMEX dongles again(I already A/B'ed them half a dozen times yesterday), the sound is sweeter w/ the aMG and much clearer w/ the OLIMEX. It's like a veil being lifted, the vocals are even less sibilating...so much for opamp rolling when an isolator makes a more drastic change, duh. The OLIMEX is so clear sounding that it's pretty hard to believe, and I'm still not used to it to be perfectly honest. It's the same difference as between DirectSound resampling(on XP) against ASIO to give a rough idea, some sort of additional nasty sounding THD distortion. That Autechre album I just mentioned above sounds pretty darn amazing now 

I know the Bravo is self-powered but it might very well be that the Tenor chip itself actually feeds the USB cable power...that would explain a thing or two, and the OLIMEX has a 12V external PSU jack