Great PC Tweak - A Bert "Must Have"

[PeterSt]

because it implies 250ps of jitter

At ordering the components I just saw that it is 100ps. Still bad but better.

[CoenP]

In the mean time, right at this moment we're applying the 24.xxx audio oscillators on USB ... See if Nick's failure on this happens here too ...

Peter

If you want it to work with an VCXO if it doesn't I think you will have to make the voltage slightly adjustable to stay within the USB chips timing tolerances...

regards, Coen

[CoenP]

I originally wondered about the Molex on the pcie card. I think this has to do with cost savings to provide for a powerfull USB3 spec 5V line (X2).

On second thought this introduces an undesirable architecture.
Now the PCIe will only provide for 3.3V, 12V and Ground. Connecting the molex a second 12V and Ground path are introduced only to harvest the 5V. Not good.

So ideally the molex is not connected. So can the card do without the 5V? The NOS1 can. We can use a separate molex adapter to feed the xtal with a "star" 5V since it is galvanically isolated. I am not shure of the latter however since three wires of the xfirmer are terminated on the clockboard.

Anyway i makes sense that the effect of the card is psi and motherboard dependent and that the mod could and should be modded!

Regards, Coen

[Nick]

In the mean time, right at this moment we're applying the 24.xxx audio oscillators on USB ... See if Nick's failure on this happens here too ...

Peter

If you want it to work with an VCXO if it doesn't I think you will have to make the voltage slightly adjustable to stay within the USB chips timing tolerances...

regards, Coen

Coen hi,

Peter is working with the audio clocks used in the NOS, they are fixed frequency and the specs are exceptional but unfortunatly they are not available in 24.000mhz. The closest frequency available is 24.5mhz, when I tried these out I could get the PC USB card to work with the 24.5mhz oscillator but not the NOS interface end at this frequency.

It would be great if they can be made to work though.

Cheers,
Nick.

[PeterSt]

Connecting the molex a second 12V and Ground path are introduced only to harvest the 5V. Not good.

Coen, exactly my thinking. And I am almost sure it will work without the Molex connection. Will try tomorrow ...

Peter

[Nick]

Connecting the molex a second 12V and Ground path are introduced only to harvest the 5V. Not good.

Coen, exactly my thinking. And I am almost sure it will work without the Molex connection. Will try tomorrow ...

Peter

Guys,

Best sound here is from powering both the USB chipset and the 5v aux usb supply from the PCIe 3.3v bus rail.

I think it is possible that only having one common power rail noise spectrum on the 3.3 volt supply to each of these systems helps prevent the NOS USB d+ d- lines, and the data transmitted from the PCIe bus the USB chipset from seeing diferential noise from separate supplies. The 3.3v power from the pcie bus rail may not be the ideal but at least there is a common noise spectrum experienced by bus components the USB chipset and in the 5v aux usb supply.

The USB card clock performs best for sound quality here with a high quality low noise separate supply but only if the clock and its power supply are decoupled from the USB card by a transformer. Leave out the transformer and prepare to listen to jitter 

In summary USB card power and 5v aux USB power from the PCIe bus and USB clock power as clean as possible but transformer decoupled clock.

Hope this is useful.

Best,

Nick.

[CoenP]

Hi Nick,

You're well Ahead of us but we're catching up!

As far as I can see now the ppa transformer does NOT galvanically isolate the clock. Two red wires are attatched to the clock output ports where one is connected to the ground. Peeking between the clock and usb board i can see that the former is connected to a (one) film capacitor which in its turn is connected to one of the old xtal pcb islands. The other island seems not connected. There is a black wire from the xfomer to the clockboard ground. This is either a screen or shield or the second leg of the x- former output. I think the latter so no isolation... Why then use an x-former? Bandwidth limitation? Voltage adaption?

I'll take off the clock board tonight and see whats really below it.

Regards, Coen

[PeterSt]

Hey Coen,

Maybe it could be nice (well for me) if you can more clearly talk about what you see. For example, your "the former" seems to refer to two (!) read wires while I think you mean one of them, which now makes not much sense (to me).
Also, you might put some attention to
"i can see that the former is connected to a (one) film capacitor which in its turn is connected to one of the old xtal pcb islands."
which to me seems wrong in the first place. Not sure, but I'd say that this "former" needs to be connected to the old xtal island which from there goes to ground through the cap. Or ?

This is all not crucial of course, and it seems that I try to help you which I don't think is necessary at all. However, I am always eager to find messed up things (designs) and this seems to be one.

Btw and might that help, an active osciallator (not voltage controlled assumed) has "inputs" for voltage and ground, and for output the one clock wire;
Running the output through a transformer might not be the best idea for the signal itself (I keep on saying that any analog device is too slow for this) but may imply groundloops again (somewhere at the other side). But the supplies (gnd and V) can sure go through the transformerS.
For real isolation it needs three transformers, but I'd still wonder what happens with the still not-isolated ground at the other side.
We (or I) can also say : this never can work unless far (!) more complicated schemes are applied, and they won't lend themselves to apply on existing designs. That's what I think of it.
Mr. Pang (I think is his name) may have found himself for the same half-decisions. Any good for the better ? I again don't think so because the result will be out of (veryfiable) control ?

Peter

[PeterSt]

when I tried these out I could get the PC USB card to work with the 24.5mhz oscillator but not the NOS interface end at this frequency.

Hey Nick,

I can't even get that to work (with the 24.5);
Questions :
Did you power the card through the Molex for this ?
Did you install the (Nec) driver or anything else for this ?

The card with the original oscillator works here with neither. So I wonder whether it needs more with the notice I can't easily pull a Molex supply from the PC (read : not all that easy to briefly try whether this helps).

Thanks,
Peter

[Nick]

when I tried these out I could get the PC USB card to work with the 24.5mhz oscillator but not the NOS interface end at this frequency.

Hey Nick,

I can't even get that to work (with the 24.5);
Questions :
Did you power the card through the Molex for this ?
Did you install the (Nec) driver or anything else for this ?

The card with the original oscillator works here with neither. So I wonder whether it needs more with the notice I can't easily pull a Molex supply from the PC (read : not all that easy to briefly try whether this helps).

Thanks,
Peter

Peter hi,

The USB 3 card that worked with the 24.5Mhz clock has an NEC chipset (2 port) using the standard windows 8 driver.

I removed the standard 24mhz crystal and its resonant caps and connected the 24.5Mhz "audio" clock. The test clock was powered by Battery and between its output and the NEC USB cards clock inputs its was decoupled through a signal transformer. The USB card was plugged into the PCIe bus for power so just standard PCIe power no use of Molex etc.

It may be the type of test you are trying, I did not do extensive testing on the card with the 24.5Mhz clock. It showed up on device manager and I could read an attached USB stick drive without problem in Explorer but it would not manage connect with the NOS.

Hope this helps.

Best regards,

Nick.

[Nick]

The card with the original oscillator works here with neither.

Sorry missed this. You have me there..

This is strange surely that should work. I know you mentioned it is hard but maybe if you can just power the card from the PCIe bus and debug from there with the standard clock in place.

Could it be  windows 8.1 driver problem by coincidence ?

Regards,

Nick.

[PeterSt]

Yea, I knew that would go wrong with my English ...

"Works with neither" was meant to be read as : Just works with the normal MS driver and without the additional Molex supply.

Ok, thanks. But probably we tweaked the 3.3V supply wrongly; this was some digging in datasheets and where to get the 3.3V from, because it is quite tough to measure while it runs in a PC case ...
(yes, a battery would have been more easy, but I didn't want to do that)

Cheers,
Peter

[AlainGr]

I was wondering... When you mention that the molex is not necessary, how to let XXHE know that the connection is established with the NOS1 ?

Alain

[PeterSt]

Alain, because it's (3.3V) just fed through PCI(e). Well, I didn't examine whether it is really 3.3V in my case (can be 5V ?) but the NOS1 doesn't need any supply through USB, so ...

Peter

[AlainGr]

I know this, but I did the test this week-end (I left the molex disconnected)... XXHE brings an error message saying that there is no sound card... And there isn't any to select... As soon as I connect the Molex, all is back to normal...

?

Alain