Asynchronous I2S FIFO project, an ultimate weapon to fight the jitter - Page 105 - diyAudio
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Old 24th September 2012, 12:42 AM   #1041
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Originally Posted by TNT View Post
Did You take mechanical interference / loopback into consideration in this project? You need to decouple the clock source (oscillator crystal) from the playback room. Tap on the (or play loud music close to the) crystal and measure the jitter!

You are right. Mechanical viberation is one of the three main sourceses to the close-in phase noise. I designed optional rubber ring suspensions on the corners of all clock boards. But there might be other solutions.

Ian
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Old 25th September 2012, 03:41 AM   #1042
AR2 is offline AR2  United States
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Originally Posted by iancanada View Post
You are right. Mechanical viberation is one of the three main sourceses to the close-in phase noise. I designed optional rubber ring suspensions on the corners of all clock boards. But there might be other solutions.

Ian
I am sure it was mentioned somewhere before, but for a late bloomers.... is there any source for rubber rings that you guys could recommend?
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Old 25th September 2012, 04:59 AM   #1043
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nah, I ended up finding they broke, but what I ended up doing was cutting some 4mm slices of 1/4" heatshrink, installing and then carefully heating with a heatgun until it reached the right tension
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Old 25th September 2012, 06:07 AM   #1044
NicMac is offline NicMac  Italy
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Medical rubber tubing cut in rings was suggested by Ian and worked a charm for me.
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Old 25th September 2012, 07:02 AM   #1045
qusp is offline qusp  Australia
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yeah I know, but I didnt have any medical tubing lying around, but i've got plenty of heatshrink, as does just about any DIYer. havent had any problems since. I also used some fine 10000grit abrasive cloth to get rid of the sharp edges on the PCB where they attach. the heat wont be a problem, just leave the clocks off when you do it, remembering they were probably soldered in a reflow oven
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Old 25th September 2012, 07:02 AM   #1046
ggking7 is offline ggking7  United States
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Would audiophile-type mechanical isolation gear be a substitute for this?
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Old 25th September 2012, 07:08 AM   #1047
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that depends, that covers complete ******** sourcery, to wrong, to reasonable, but how exactly were you planning to use that sort of thing inside the case? remember we want to decouple the clock board from the rest of the build, but we want to keep it close to the dac board, which emits vibration of its own along with the PSU. isolating the chassis assuming what you have isnt a silly spike that doesnt actually spread energy at all, you will still be left with at least half the problem.

why bother? the clock board is perfectly set up to use its own mechanism that actually works and costs virtually nothing in parts or time; why would you substitute something of dubious benefit?

but what are you talking about? i'm always wary of things labelled 'audiophile'
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Old 25th September 2012, 08:02 AM   #1048
marce is offline marce  United Kingdom
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There are numerous anti vibration products available such as AV mounts fromthe likes or RS and other more bespoke companies. These unfortenatly are not audiophile grade*, but used for such things as mounting control boards and other electrical equipement in tanks, helicopters on the side of generators etc. The advantage of these solutions are that they can be tailored to certain frequency ranges.
*they are designed using science and physics, and work without reams of psudoscientific write ups

Having done work with high vibration situations, I would worry at the volume levels required to vibrate a crystal on a board in a case enough to cause problems. its the same with MLCC caps, tapping them does indicate microphonic action (X7Rs) but have found it hard to create the vibration levels in the real world where this becomes a problem. Though if the equipement is mounted on a surface that resonates with the music then you are going to introduce vibration.
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Old 25th September 2012, 08:51 AM   #1049
qusp is offline qusp  Australia
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yep for sure, perhaps nattonrice would like to show some pics? hes gone a bit nuts with vibrational decoupling in his dac, built with his usual skill and enthusiasm, but all stuff that will actually reduce vibrations; no Less Loss Blackbody's here. the dac boards are mounted to thick teflon base boards and then mounted with vibration mounts similar to this

Click the image to open in full size.

I actually do think there is something to this given jitter is at its most harmful in the very low frequencies, more worthwhile than some other popular tweaks anyway, when we are shooting for uber low jitter and given the fifo removes so many fun tweaking areas from the playing field.
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Old 25th September 2012, 09:24 AM   #1050
marce is offline marce  United Kingdom
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I agree, if you are going all out for the ultimate then go all out. though mounting the boards on standard Av mounts would do the trick, with a very heavy base plate for mechanical mass is reccomended. Even if I personaly think some may be overkill, I'd rather see over engineering for the full on audio system than what you do seeoften on this site, ahalf arsed attemp at the ultimate.
I would like to see a DIY project where everything employs the ultimate engineering, 10-14 layer PCB's AV mounts, etc etc (similar to what i do during the day realy).
The majority of the tweeks I see regarding clocks on this site are more detrimental to the clock signal than leaving the dam thing alone, this is one of the few threads on clocks that does emply engineering and class components, insted of wires everywhere, impedance mismatches and general bodging.
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