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At last... (Audiolab) - part VII

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JohnW said:
I love it – OH Tim, sorry to tell you, that Squeezebox Touch you sent me to CZ sadly got lost in the post… ;)
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Ha ha, nice try!

I think my last post crossed with yours, I've only just read your detailed reply about the MDAC jitter attenuation. Enough said i think.

I should be picking up the MDAC from Bartletts when they get the first batch in, so Ill give the SB3 a bash and see what happens. Sounds promising though :)

And glad to hear the poor spdif sound probably wasn't just in my imagination!!
 
Hi John

It works on the young dac (i.e. music plays fine), it just doesn't make any sonic difference on the Young Dac. SQ warned me it might not.

They Young (as I understand) terminates the power through the USB input.
 
Neil Gilbert said:
Anyone? I guess you are all stereo only.

I plan to use this between a squeezebox Touch and the Tag
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If you want to use the MDAC as a pre then you would have to use a digital coax output from the TAG and this has to be stereo pcm out I believe the TAG is spdif. This is not avail if you have the ac3 rf interface fitted. I'm not sure if the stereo output would be active with none stereo sources. I'm also not sure how easy/dynamic it is to switch the input source for the digital coax output.

Then you would have to route your L/R analogue outputs directly from the MDAC to power amp and not from the AV32R.

I don't think you'll be lucky enough that the digital coax on the AV32R will output stereo only for multi channel sources. I'm not sure how you would manage the volume when the main left right channels are controlled from the MDAC and the remaining C, SR , SL are via AV32R. Its just to messy, I'd wait for the bypass for your AV sources. Plug your stereo sources directly into the MDAC and find a suitable input on the AV32R using fixed output from MDAC. Unfortunately you are already using the analogue bypass inputs on the TAG, which is what I will be doing until the bypass unit is released.
 
As long as you don't request a sample rate that the USb isolator can't pass the Young doesn't care if it's in line or not. The 5v line into the Young from the USb is simply used to indicate signal is present, once done its dumped via relay to ground, the signal lines go through two small transformers and are additionally chip decoupled as well prior to hitting the Xlinik. It's a good design, the digital section is as good as anything, the PSU side using switching regs, less so.
 
bottleneck said:
Hi John

It works on the young dac (i.e. music plays fine), it just doesn't make any sonic difference on the Young Dac. SQ warned me it might not.

They Young (as I understand) terminates the power through the USB input.
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Are you not using it for other sources perhaps a PC ? I noticed it's in the classifieds. Shame as I've just received mine a couple of days ago. My main use will be removing all the nasties from PC source. Experimenting to see how good it sounds from a standard laptop, for Spotify and hi-res downloads 24/96
 
I think the positive benefits (or otherwise) of a usb isolator are highly (possibly entirely) dependent on the characteristics of the connected usb device.

Don't know what either of you have had upstream but I'd guess it'd make a difference with a 'bog standard' pc - something electrically noisy.

Do either of you have any form of mains conditioning, filtering or suppression on your hifi?
These would all diminish any potential effects of usb isolators.

(btw, not doubting that the good inherent design of usb input isn't the prime reason for minimal/no effect)
(btw 2, I don't believe switching regulators are necessarily inherently bad, but certainly have to be well implemented to be good)
 
JohnW said:
Apart from the Jitter results, this Squeezebox Touch is Brilliant – why would anyone spend more on a streamer??? – I really so no reason for us to do our own!, the Touch is so cheap – nice UI etc…

I love it – OH Tim, sorry to tell you, that Squeezebox Touch you sent me to CZ sadly got lost in the post… ;)
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Haha. If you have an iPad to hand try downloading the Squeezepad app to remote control it John - a great package.
If only the good John Swenson and co could solve the USB output issue so we could avoid all that jitter when feeding a CDQ...
Or is there a way you could ally the Squeezebox Server software to your streamer?! Then we'd have all those tricks and convenience, a lovely remote interface through iPad, PC or mobile, AND top quality sound.
Best, Duncan
 
dlcastles said:
Haha. If you have an iPad to hand try downloading the Squeezepad app to remote control it John - a great package.
If only the good John Swenson and co could solve the USB output issue so we could avoid all that jitter when feeding a CDQ...
Or is there a way you could ally the Squeezebox Server software to your streamer?! Then we'd have all those tricks and convenience, a lovely remote interface through iPad, PC or mobile, AND top quality sound.
Best, Duncan
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Now that I would be interested in ... on the other hand I might just buy an MDAC, or wait for the QMDAC (if that is what it's called) instead.

I heard the CDQ being demoed by John W about a year ago, just before the start of this thread.

It is a top quality product and I have been biding my time.

There are always going to be new features coming down the line, because innovation seems to be at the heart of these units.

Jack
 
Trying to understand why the MDac allegedly can be immune to jitter thru its multiple jitter reduction stages (primary pll, secondary (digital dual dynamics? pll), ESS asrc), but the same can not be said for the raw power supply ?

Here the External raw power supply properties propagate thru several cascaded isolation buffers like RC filters, 26 internal regulated supply rails with 10 ultra low noise, low impedance discrete regulators.
Still, an “upgraded” raw supply will be audible…

I’m really trying to understand how this external power supply could still matter, depsite all the local isolation and filtering inside the MDac ?
 
JohnW said:
Hi Tim,

After doing so more measurements on the SBT I'm not sure if Clock-Locking worth the effort and here's why:-

The SPDIF output Jitter of the SBT streaming 44.1 kHz via Coax:-

Around 1nS RMS (Really Noisy Measurement)
Around 17nS Peak (Really Noisy Measurement)

But after the first 2 stages of Jitter Attenuation by the MDAC (Measured at the MDAC's Re-clocked Digital output):-

10pS RMS (Noise Floor of my Rohde & Schwarz UPD here in CZ)

80pS Peak (Noise Floor of my Rohde & Schwarz UPD here in CZ)

The MDAC's Jitter Attenuation circuits have reduced the SBT's Jitter to a point that I wonder if it’s worth going to any more effort. I'd expect MDAC's Jitter results are better, as it would appear that I'm just measuring the UPD's Noise floor.

Don't forget that after the first two stages of MDAC's Jitter Attenuation - comes the final stage of Jitter attenuation, the ESS's ASRC (The MDAC has 3 cascaded Stages of Jitter Attenuation)...

We need to get you an MDAC, so you can see if you’re happy with the MDAC / SBT combo.

The MDAC's reclocked Jitter levels are so low, that I had to confirm the R&S UPD was indeed locking to the MDAC's Digital output.

I hope I’ve not made an error in measurement – I have nothing to double check the measurement results against.

I did measure a CD player to confirm the UPD’s not had a mental breakdown or something, and results looked as expected, so I really do think the UPD’s ok…

John

P.s. the "Rohde & Schwarz UPD" is a Digital / Analogue measurement Analyser
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Would also be fascinating to find out what implementing some of these tricks does the Touch's jitter...
http://soundcheck-audio.blogspot.com/2011/11/touch-toolbox-30.html
 
ChrisPa said:
Do either of you have any form of mains conditioning, filtering or suppression on your hifi?
These would all diminish any potential effects of usb isolators.

(btw, not doubting that the good inherent design of usb input isn't the prime reason for minimal/no effect)
(btw 2, I don't believe switching regulators are necessarily inherently bad, but certainly have to be well implemented to be good)
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No mains coniditioning or filtering in my system.

Is it not the noise produced from the internals of a PC which finds its way down the 5v USB port we are trying to supress. I guess if the mains in is noisy to begin with and no effort is made internally in the PC to filter it, then its the cr*p in cr*p out scenario. This area is not clear to me at all. The idea of a badly isolated device injecting RF into a system. Are we talking specifically hifi here or anything which is on the same ring mains ?.
 
@Rboer,
You are right, any properly designed DAC shouldn't be affected by a better PSU, that why many pro audio equipement usually use standard walmart and any suggestion that they could be improved with a better PSU is usually met with disdain by their engineers.
John W admitted he didn't measure anything concrete and he just "believes" it would improve the sound. Sadly being a talented designer or a Nobel prize doesn't make you immune to placebo.
 
Seranil and rbroer

You are shilling.

And you are from/represent/are fanbois of another company with a flea in it's ear.

I claim my five quid. (each)

:rolleyes:
 
JohnW said:
The MDAC's Jitter Attenuation circuits have reduced the SBT's Jitter to a point that I wonder if it’s worth going to any more effort. I'd expect MDAC's Jitter results are better, as it would appear that I'm just measuring the UPD's Noise floor.
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Hi John, Been having a think.
Would it be a lot of work for you to throw together a clock input on my SBT regardless? Doesn't have to be anything elegant as long as it works, and I'm certainly not in any hurry for it. (note my cheeky use of "throw together" which makes everything sound easy even when it is extremely difficult :D)

I realise this is 100% hifi paranoia, and your measurments really do speak for themselves, but due to my own psychologcal flaws as opposed to any technical ones I think I'd struggle to accept the jitter-attenuated solution until I'd compared it to the clock-locked equivilant. This probably comes from my DaCapo owning days where removing the clock-lock would make such a real and obvious difference. Hard to shake it off!

At the moment I don't have anything with a clock input for comparison, and I guess even if I did, a clocked v unclocked SBT would make for a much fairer test. Honestly though, if it would tie you up for too long (i.e. more than the time it would take to eat a couple of pot noodles) then please tell me to eff off, you've already been a great help.


Cheers,
Tim

edit: did you see how I shifted the blame for my obsession onto you by mentioning the Dacapo?
 
. You are shilling.

And you are from/represent/are fanboisof another company with a flea in it's ear.

I claim my five quid. (each)
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Agreed. This is why anonymous posting is sometimes a problem.

Admin: can you do an IP check please?
 
Why all the paranoia? In my case you are abloslutely wrong. I am just an objectivist that get annoyed at all the non-sense and "Hi-Fi" wizardry found on audio forum.
When you are done with your IP check I will send you my Paypal address so you can send my fiver ;)
 
Mr Toy,

You really need to seek professional help...

To get this... uptight on an internet forum cannot be healthy.
 
Oh dear this thread has become infected with misdirected* wannabe consumer savioury.

*JohnW being a such a nice chap.

I think Baz might have twigged what c - b - t stands for....

Especially that it wasn't actually me who suggested that there were shills abound...
 
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