Hey Peter - First of all this is a totally brilliant Forum we are all honest and objective (as far as mere humans can be) and there is none of the stupidity of other Fora. For three people (and more!!) in three different locations with different systems and room acoustics (and different ears) to come up with stuff that is even close to objective does not happen anywhere else on the WonderWeb.

Nick and I (the "choir boys") are holding back on that visit to the "Altar" only because you put us off (as I perceived it) pending outcome of your "ubiquitous" clock experiment. No problems let me/us know - I wait here like a "coiled spring" ready to come over (even knowing that it will cost me that Scotch ha ha).

Meanwhile - my wife has insisted that I demonstrate the difference between Dexa and none Dexa - now that really will be interesting!! also she has shown particular interest in my "heavenly trimmer". MMmmm.

Cheers

Paul

I have Dexa clocked 2 pcie cards with NEC D720201 (only because I had them lying around) and D720202 chips respectively and very different board implementations - I cannot hear any differences - certainly nothing significant compared with the other things that are going on in my system at the moment - not sure if that means anything at all (I have not checked data sheets at all) but I share it for what its worth!!

Oh and both cards were powered from the backplane - ie the molex was not plugged in.

Paul

Peter - Wow not sure I follow all of that will have to re read a few times. For sure I do not recognise all you mention in terms of SQ but just a couple of quick notes about the sound quality I get with Dexa's

1  With Dexa's I do NOT get more bass as such. I DO get more speed and "snap" even at low volumes it is noticeable. In some situations with Dexa's it even sounds as though there is less bass but it is because (I think) it is cleaner and more controlled.

2 With stock NOS1 if I stand up and walk around the room I can hear bloated (arrghh horrible) bass in certain areas (my thin odd shaped room is probably more like an organ pipe ha ha) but with Dexa's if I stand up and walk around sure the bass emphasis is still there but it sounds soooo much better quality.

3  I definitely do NOT listen at lower volume with the Dexa's I do not perceive any difference in volume. In this respect I do NOT concur with Nick. There was a hardness to the sound to begin with but that disappeared with a week running in of the Dexa's.

4  Compared with Dexa's the standard NOS1 has a slight digital "glare" or "haze" - the Paul Pang card in place of the pcie sounds warm analogue but does not seem to do achieve anything like the Dexa'd pcie card achieves which simply seems to remove nasties.

What I hear now is that the Dexa's easily set the bench mark qualitatively - absolutely no question to my ears (even just considering removal of "nasties"). Then there is Paul Pang and stock NOS1 - now have heard the bench mark the difference between Pang and stock pcie card is more a question of flavour.

There is a big caveat though - my NOS1 has some other mods to do with distributing capacitance on the USB board and changes in types of capacitors elsewhere (I know very naughty !!! - and I know it needs its noise profile re-calibrating Peter) - I will soon be installing Dexa's in the stock NOS1 so watch this space.

Cheers

Paul

OK using Mani's standard NOS1 I have been listening with it connected to a mobo USB2 port. Both USB2 & 3 on the mobo switched on. I guess there is no need to describe what I hear because most NOS1 users out there should be familiar with the SQ.

Next I switched over to the Paul Pang card - there is a clear difference in sound quality. The sound becomes "fuller" less thin definitely a more "analogue" sound. Perhaps "Lush" would be a way to describe it and at first listening I would have said that it was tonally better - but now having heard the Dexa USB I am not so sure maybe it just sounds "fuller".

However, with the benefit of now having listened to the Dexa clocked USB link it is clear that the Paul Pang card does not improve on the clarity of the sound. But it certainly changes it.

Hope that helps

Paul

Mmmm  as it happens I have one of Mani's NOS1's here (totally standard no mods) so I can compare it with my modified NOS1 with Dexa's. I can try any combination (1 Dexa, 2 Dexa's, std NOS1, modified NOS1 etc) except I do not have a standard Pcie USB3 card - both mine have been hacked so they no longer have crystals in them one of them is being clocked by a Dexa.

So for various reasons the only tests I can do are against mobo USB2/3 which I can turn on.

Is that any use to you Peter?

The only other thing is I have to re tune my ears because I have been listening to a number of combinations and I am starting to show the first signs of madness (OK maybe not for the first time.......)

Oh and of course I have a Paul Pang card in and working...

Cheers

Paul

Just a point about the "heavenly trimmer" the point where the sound has a slightly hard edge to it is where the Dexa cards trimmers were factory set. I would have to assume that the Dexa's are set very close to 24Mhz in testing simply because they can be!! So maybe the slightly hard edge comes when the two Dexa's are very close in frequency.

Nick is that what you found?

Wish I could measure it - Nick presumably you could see the two clocks on your funky scope?

Paul

Hi Coen - This is my second pcie card both have exhibited the same problem. What I will do is try Nick's he was expressing an interest in coming down here soonish. Nick does not have this problem.

P

Hey Nick - I did exactly the same and just moved slightly away from the point where the sound had a slight edge.

I was expecting that maybe the ps would need some running in (and maybe it does) but the sound is really smooth and just effortlessly glides through difficult pieces. String quartets are sounding wonderful.

P

I can confirm my PC does not recognise the pcie card when there is no clock in it (when the crystal is removed) or when the Dexa signal is not switched on.

I have another problem and that is when I reboot my PC with the pcie card clocked by the Dexa (and the Dexa switched on) the Bios does not fire up correctly - I always have to reset the Bios just as the reboot starts and then select default Bios values - then and only then will the PC boot. The output of the Dexa clock to the pcie card is completely isolated as it comes out of an isolating pulse transformer. I have replaced the BIOS battery on the mobo earthed the Dexa card to the PC but none of this makes any difference. Also I powered the pcie card from a molex supply from the ATX but again made no difference.

If I remove the card I can get the PC to boot properly.

Any ideas Gents would be appreciated.

Cheers

Paul

Anthony - thanks for the clarification the one that I did get the back of my finger on was quiet warm hence the erroneous assumption.

P

Ha ha the replacement power supply for my Dexa arrived today. What a relief to get two Dexa's back into service. Oh my the sound quality is just stunning with 2 Dexa's. The fantastic bass is back and just as fantastic everything else.

Anyway now that I have two Dexa's again I have been playing with the "heavenly trimmer". And this time the effect on sound quality is unmistakable. From the as delivered setting a quarter turn one way makes the sound softer. A quarter turn in the other direction again seems to make the sound softer but also a refined sound. After just a short time it is not possible to say which sounds correct or even the best - it does not sound clear cut.

Paul

Maybe Paul Pang is using regulators to derive 3.3v from the 5v rail hence the chunky heat sinks - dc-dc converters could be expected to significantly more noisy.

P

Hey Peter - I am not sure if this helps but it might. The Paul Pang pcie USB3 card is a standard NEC based pcie card with a piggy back board (added by Paul Pang) that has the low jitter clock on it. On both the main board and the piggy back board there are regulators that get warm each with a lump of Al glued to them - certainly added by Paul Pang. The card has to have a Molex ps  or it will not work and it only uses the 5V supply on the MOLEX - mine only has the 5V connected so I know it does not need 12V.

That might indicate that the standard pcie card does not need 12V - maybe!!.

Paul

So with Dexa in NOS1 and Pang pcie at the PC I adjusted the "heavenly trimmer" as far as I could but I can't honestly say I can hear any difference - just now it is hard to tell if it is having any effect at all.

Maybe the Pang card clock is not close enough to the Dexa clock in frequency.

Paul

Hi Alain - NOS1 is "asynchronous" but the way the data is transferred is maybe not strictly that. I think (and I am sure Peter will correct me if I am wrong) that when NOS1 is ready (i.e. its receiving buffer is running low) it requests a block of data to fill it ("bulk data transfer"). So Nos1 is the Master and the PC is the slave. That is why on the face of it, it is hard to understand how jitter in the USB link can be a problem because (I think) the data is transferred with timing information and so should be immune to the effects of jitter. I am sure that is why Peter thinks this is all about noise.

Another possible way of transmitting over USB is Isochronous which means that the data is transmitted equally spaced - but I am pretty sure that is not the way NOS1 works and I am also sure Peter will very soon correct me if I am wrong.

Cheers Paul