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Tweaking an ESI Juli@ XTe card
Tweaking an ESI Juli@ XTe card
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Old 11th March 2015, 06:45 PM   #21
nige2000 is offline nige2000  Ireland
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L C Audio Technology / General Instructions

reference
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Old 11th March 2015, 08:39 PM   #22
SGK is offline SGK
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Hmm good question. I did not fit the clock. I have sent a note to FA.
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Old 12th March 2015, 01:46 PM   #23
SGK is offline SGK
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I raised this with the guys at FA. They responded:

Quote:
The ground return goes back to the psu. You always want to take noise away. The clock should not be grounded at the signal end. It is bad practice to connect the ground up at the clock end. What you should do is use a coax for the signal with the ground connected at the clock but not at the destination end.
I'm still trying to understand this. (I sent them the link provided by Nige2000.)
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Old 12th March 2015, 02:18 PM   #24
Greg Stewart is online now Greg Stewart  United States
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Tweaking an ESI Juli@ XTe card
On clock removal, I tried a couple of things last night.

The trick is that the long SMD leads under the clocks have to be sufficiently heated to loosen their solder joints before one tries to move the clock. I don't think my hot-air station would do this.

Best was using two soldering irons coming in from opposite sides of a clock. Prepare by tinning each terminal with a medium-sized blob of solder to ensure good heat transfer.

Then touch and hold the irons on each and apply a very slight pressure to move the terminals. When the solder is sufficiently softened, they will begin to shift. You can then GENTLY push them until you have cleared the pads underneath.

I was also able to do this with one iron moving one side at a time just a slight distance, then switching over to the other side, heat and move it a slight distance, repeat until the clock is loose. But this method has a greater danger of damaging the pads.

Trying anything to move the clocks before the solder is loose WILL damage the pads.

And as I said, a hot air station is not the right tool for this as the SMD leads extend a long way under the clocks AND are insulated by the plastic base. It would be very hard to heat them up sufficiently with a station.

My 2 cents on this.

Greg in Mississippi
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Old 14th March 2015, 02:29 PM   #25
marce is offline marce  United Kingdom
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Tweaking an ESI Juli@ XTe card
Quote:
Originally Posted by SGK View Post
I raised this with the guys at FA. They responded:



I'm still trying to understand this. (I sent them the link provided by Nige2000.)
Sorry, but this is so wrong.... The power should have its own twisted pair connection and the clock signal should go to the board via twisted pair or coax with its return (ground) soldered as close to where the clock signal is as possible on the board. To recommend anything else is sheer stupidity and shows no understanding of how critical clock signals or signal integrity (or EMC engineering). Having the clock return go via a long torturous route via the power supply is stupid....
EMC and signal integrity are two sides of the same coin, with that in mind read this rather humorous look at how NOT to do things from one of the Guru's regarding this sort of thing.... The first point he brings up is the pertinent one.

The 10 Best Ways to Maximize Emission from Your Product

The instructions put up by Nige2000 say the same as I do, as do instruction for the Tentlabs clocks....
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Old 14th March 2015, 04:29 PM   #26
SGK is offline SGK
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I'm inclined to agree with you but then I am a novice at this sort of thing and not really in a position to debate it hard with the folk from Fidelity Audio UK.

I also find it somewhat intriguing that the LC Audio instructions appear to show no GND connection at the clock side. Yes the shield is connected on the device but doesn't appear to be shown connected on the clock.

I'm now wondering what, if anything, I can do - particularly given the damage caused by removal of the oscillators...

PS: in contrast to the LC Audio instructions, FA also said to remove the resistor.

(Re clock removal, yes two soldering irons at the same time is likely the best way to go. I, however, only had one.)
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Old 14th March 2015, 06:01 PM   #27
SGK is offline SGK
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Quote:
Originally Posted by jan.didden View Post
Guys I am willing to part with my ESI Juli@ card, it's about a year old but am not using it anymore as I have got a used dScope III.

Anybody wants it, make me an offer. I'm located in Belgium.

Jan
Which version is it, PCI or PCIe (XTe version)?
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Old 14th March 2015, 06:28 PM   #28
nige2000 is offline nige2000  Ireland
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pci version
sorry I have it now
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Old 14th March 2015, 07:56 PM   #29
marce is offline marce  United Kingdom
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Tweaking an ESI Juli@ XTe card
Quote:
Originally Posted by SGK View Post
I'm inclined to agree with you but then I am a novice at this sort of thing and not really in a position to debate it hard with the folk from Fidelity Audio UK.

I am though
To be perfectly honest I find most of these add on clock board worrying, clock signals should be short (as short as humanly possible) which is why on most good PCB design the clocks are placed as close as possible to a devices relevant pins or if this is not possible some thought of correct termination of the transmission line. Taking the clock of-board is never a good idea, but if it is done it should be done with the uttermost care, preferably with some buffering to drive the long lines created by being off-board, a bespoke clock buffer being the best solution.
The clock daughter card must have a thick low impedance supply lines especially the Ground to minimise any chance of the two boards grounds being at different potentials. The clock signal itself should be transferred preferably by co-ax and miniature rf connectors or similar, the signal having its own ground connection connected to the main PCB as close as possible to the point where the clock signal enters the board.
To do anything less is more likely to create a clock that performs worse than the one being replaced and may also add more noise to a system due to EMI, negating the point of the modification...
A bit more on signal propagation....
http://www.x2y.com/filters/TechDay09...%20_JohnWu.pdf

Your PCB can be re-worked with care, have a look at this...
Circuit Board Repair and Rework Guides
http://www.intertronics.co.uk/resource/guide1.pdf
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Old 15th March 2015, 10:53 AM   #30
Crom is offline Crom  United Kingdom
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Guys, I'm following this with interest.

In case it's any help, when I've removed oscillators from boards I've done it by melting the solder on one pin and then immediately (and very slightly/gently) levering the same end of the clock up with a thin scalpal blade - or other very thin thing! Then go to the other end and repeat. Try to keep the heat to a minimum but it works for me.

Re the grounding points for the clock signal. I agree that theory dictates the closest point to where the clock signal attaches to the board and also that sending it via the psu is nuts. However, a couple of points: firstly the closest point on the board may not be the closest electrically...I've had to fiddle around trying to find the best ground point to get motherboards to boot and sometimes it's not been the closest physically . Secondly, I'm not convinced that it's the improved clock signal that is contributing to the improved sound that we're hearing. When I've replaced clocks on motherboards and I've measured the clock signal before I've removed it, I usually find a perfect sine wave...literally textbook. However, often the clock signal that I replace it with is certainly not perfect. Not sawtooth but more like sine with kinks in it! Anyway, the point is (and I seem to remember nige2000 saying similar somewhere) that it's the improved power supply to the clock that is actually the major contributing factor here rather than the signal itself.

This would seem to tally with projects like Ian's FIFO where the clock supply massively affects the sound coming out the other end.

Hope this helps,
Crom
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