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MDAC First Listen (Part 00101001)

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Sorry for interrupting the regularly scheduled program but as a relatively late backer, can I ask a few small questions?

1) What is this USB Detox Development option? Is it part of the MDAC2 or something totally different?

Its a standalone unit that can work with any DAC, but with its Clock-Lock interface is designed for optimal performance with the MDAC / FDAC.

2) Is the MDAC2 mainboard still going to be shipped by itself and the case and HQ PSU developed at a later stage?

I'm still waiting on confirmed pricing, but I'm very VERY strongly leaning towards shipping a complete unit with FWC and HQ PSU. In fact since my return from HK I've been reworking the Analogue PCB in this direction.

3) Where exactly is John at the moment? Is he developed globehopping powers so he can be in multiple places?

I'm back in Czech Rep. until I'm next in HK early October hopefully to approve the VFET / FDAC chassis, start the production cycle for the FDAC analogue PCB & Detox and visit the HKTDC electronics show.

4) Has the company still got my details so I can be informed when it's payment time?

Yes Renata has everyone's details - Renata will confirm your payment statues as we still have not officially requested the MDAC L2 development instalment.
 
From here:
"Rise and fall time measurements for USB compliance
Mandate: Required
Effective Date: August, 2007
There has always been a problem accurately measuring rise and fall times, especially on high speed devices. The measurement of interest is the edge rate, or slew rate, during the state change time. To help improve accuracy of the measurement, the USB-IF is standardizing on one test fixture for high-speed signal quality.

Aside from the fixturing and probes used to take the measurements, major contributors to the inaccuracies in these measurements are the shape of the edge, noise on the signal and the method of calculating the 10% and 90% points as defined in Sections 7.1.2.1 and 7.1.2.2 of the USB 2.0 Specification.

A waveform with slow corners (see sample eye diagram below) will result in a measured rise time that is slower than the actual edge rate would indicate. Also a small change in the position of the 10% and 90% points due to noise on the signal, etc., can cause a relatively large change in the measured rise time."

USB 2.0 HS defines the fastest edge rate crossing speed as 100ps with a warning given for 300ps so any edge rates faster than 100ps will fail but it doesn't mention the slowest edge rate but the maximum interpacket delay times give an idea of this "So the maximum interpacket delay of a host's response to a device is <= 264 bit times + 60ns, which equates to 610ns or 292 bit times."
Thanks for this. I'm tempted to write to HFN and ask PM to show his workings. Chances of that letter being published?
 
Adam, isn't he just describing it away with that slower/ faster corners bollocks. Reducing noise gives faster corners, faster corners give a faster edge rise time that is cloiser to expectations based on the slope alone.

Seems to me like he's admitting its just a measurement frig.
 
I am sorry for my questions regards this Detox think. But I did not see the advantages. .....
What is the advantages to reclock the data within the transport to the fdac? The fdac will do the job anyway. ...
Having in mind that the Detox offers no galvanic isolation.
And use anyone one of these Detox at the beginning and end of a USB cable?
Thank

Regards
F.s.
 
+1.

If JohnW says an increase in SQ for the MDAC is/maybe possible with this proposed USB-Hub device with its own Linear PSU...I'll take such a unit....worth a punt I guess, if it's below the £100 mark?

A single box if possible please.....I don't like too many gubbins!

Also since this is expected to help iron out quality control issues for the FDAC......And it gives me something to play with while I wait for the FDAC...I'm in....:D

I think John said about £130, and so far as I remember it is expected to have a separate LPS. I agree about having too many boxes, but keeping the PS well away seems a good idea.
Edit- I left this thread for a day, and I was about 5 pages behind! This note is a bit superfluous now. For the record, I have paid up also.
 
Adam, isn't he just describing it away with that slower/ faster corners bollocks. Reducing noise gives faster corners, faster corners give a faster edge rise time that is cloiser to expectations based on the slope alone.

Seems to me like he's admitting its just a measurement frig.
Oh yes it could well be. I get that. Have you seen the HFN article though Simon? the frankly the two eye diagrams look so similar that I still can't see it.
 
Oh yes it could well be. I get that. Have you seen the HFN article though Simon? the frankly the two eye diagrams look so similar that I still can't see it.

Is the article only in print or can you post the eye diagrams- what is the x-axis (time) scale?
 
Adam the eye patterns could be all but identical just varying at the edges but with almost identical uncertainty elsewhere and still hit that reduction %.
 
Assuming sonic differences are down to RF getting into the DAC then eye pattern analysis will only be a side issue. We need Detox with associated tests. I'd ignore the HFN article.
 
And use anyone one of these Detox at the beginning and end of a USB cable?

F.s.

I am currently using a Jitterbug on one end and a Regen on the other. The fact that both have a positive effect suggests that John's 3-stage solution will be better still - and that one will be sufficient.

Mine was almost certainly an extreme case - in hindsight a windows laptop plus MDAC/Meridian amp/Focal Utopia speakers was a seriously bad idea and it's taken a while to overcome the noise problem. Now that I have, it's great, and I appreciate how much detail was hidden in the noise floor.

We know computers are inherently noisy and that USB wasn't designed with music in mind: what's harder to grasp is that noise that you can't actually identify as such (it's not obvious, like tape hiss, for example) can nevertheless affect the sound. The effect of cutting it right down is akin to seeing HDTV for the first time.
 
If using the USB detox, will we still need USB 2 hubs to get the best out of the Squeezebox solution with the MDAC1?
 
I am currently using a Jitterbug on one end and a Regen on the other. The fact that both have a positive effect suggests that John's 3-stage solution will be better still - and that one will be sufficient.

Mine was almost certainly an extreme case - in hindsight a windows laptop plus MDAC/Meridian amp/Focal Utopia speakers was a seriously bad idea and it's taken a while to overcome the noise problem. Now that I have, it's great, and I appreciate how much detail was hidden in the noise floor.

We know computers are inherently noisy and that USB wasn't designed with music in mind: what's harder to grasp is that noise that you can't actually identify as such (it's not obvious, like tape hiss, for example) can nevertheless affect the sound. The effect of cutting it right down is akin to seeing HDTV for the first time.

Yes, well stated & a point that was being made on this & other forums for some time now. We may find, when some measurements emerge, that the spectrum of this noise is the defining issue? As JohnW already said "LF Jitter really impacts the sound stage"
 
I am currently using a Jitterbug on one end and a Regen on the other. The fact that both have a positive effect suggests that John's 3-stage solution will be better still - and that one will be sufficient.

Mine was almost certainly an extreme case - in hindsight a windows laptop plus MDAC/Meridian amp/Focal Utopia speakers was a seriously bad idea and it's taken a while to overcome the noise problem. Now that I have, it's great, and I appreciate how much detail was hidden in the noise floor.

We know computers are inherently noisy and that USB wasn't designed with music in mind: what's harder to grasp is that noise that you can't actually identify as such (it's not obvious, like tape hiss, for example) can nevertheless affect the sound. The effect of cutting it right down is akin to seeing HDTV for the first time.

I have exactly the same impression using a Green Regen into a Supra cable into an Amber Regen. The cascading certainly makes a difference, so John's triple cascade should be brilliant.

I don't know that your laptop is an extreme case- I have a dedicated Mini with all the tweaks I can manage (LPS, no wireless, Uptone Audio MMK fan power, SSD but run from SD card and RAMDisk for music, Audirvana2, stripped-out OS) and the Regens still make a big difference.
 
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