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Old 5th October 2011, 04:42 AM   #1
diyAudio Member
 
Join Date: Oct 2011
Smile Goldy(1)_Oscillator FAQ

Hello, I am Goldy from China. I have been worked in oscillator area for many years.
last year a friend asked me to help him on oscillator, (P.S, he is an HiFI DIYer). then I started to know oscillator used on Audio system.
I would like to share information what I learned.
Here if you have any questions about oscillator,
such as :
Is TCXO good or OCXO?
Good temperature oscillator will help my CD player?
Is jitter important?
How to calculate jitter?
What's phase noise?
Where should I find a good oscillator?
etc..
you can write email to goldy_zhang@hotmail.com or leave message to me.

And you can visit the website,you will know what you need for oscillators.
GOLDY论晶系列(1)------晶振专家之提问篇 - 音响DIY论坛 - HIFIDIY论坛 - Powered by Discuz!

if you can not read Chinese, please try google translation.

Also I am very interesed in audio system. I am still working/researching oscillator in this area.

thank you.
Goldy.
10-05-2011
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Old 5th October 2011, 05:23 AM   #2
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Hi,

I'd be very interested to know your opinion of the relationship between power supply noise/ripple and oscillator phase noise. Have you done any testing with different power supplies and the phase noise of a tcxo/ocxo etc ?

I'm thinking about building a clock with a Crystek CCHD-957 hcmos xo and an Analog Devices adp150 regulator. It can be powered from a 3.7V li-ion battery and this can be charged through the Microchip MCP73861.

http://www.crystek.com/crystal/spec-...k/CCHD-957.pdf

http://www.analog.com/en/power-manag...s/product.html

http://ww1.microchip.com/downloads/e...Doc/21893E.pdf

and a buffer like a 74VHC04, or a 74HC163 to create multiple outputs (create 11.2896Mhz from 22.5792Mhz xo).

I am also interested in Nichicon's PLE capacitors for this.

http://www.nichicon.co.jp/english/pr...lid/pict_f.htm

Maybe we can start a project and get some PCBs done ? A 5cm x 8cm PCB will fit perfectly in a small case like this :

http://www.hammondmfg.com/pdf/1455C802.pdf

Click the image to open in full size.

I expect a lot of people will be interested in a clock this good.

Thanks,

Tom

Last edited by KlipschKid; 5th October 2011 at 05:50 AM. Reason: Add project details
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Old 5th October 2011, 06:02 AM   #3
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The charge controller circuit :

Click the image to open in full size.

can run from 5V and outputs 4.2V. Very convenient. A remote controlled helicopter battery should do fine at 3.7V 600mah.

The regulator circuit is very simple :

Click the image to open in full size.

Last edited by KlipschKid; 5th October 2011 at 06:25 AM.
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Old 5th October 2011, 07:25 AM   #4
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Charge controller circuit for 16 pin soic and 500mA charge rate - what do you think Goldy ?

Click the image to open in full size.

And here is a cheap low noise 5V regulator.

Click the image to open in full size.

Last edited by KlipschKid; 5th October 2011 at 07:48 AM.
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Old 5th October 2011, 08:14 AM   #5
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Apologies if this seems an overwhelming response ;-) Here is the phase noise for the CCHD-957. Very impressive eh ? It is +/-25ppm.

Click the image to open in full size.

Last edited by KlipschKid; 5th October 2011 at 08:18 AM.
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Old 10th October 2011, 03:06 PM   #6
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CCHD-957 model phase noise is good.
BUT, for this package ,45.1584MHz and 49.152MHz must be 3rd overtone AT crystal. I am not sure this company can do this? it is difficult to find this kind of crystal, but maybe they can.
You'd better get some samples and test them! I can help you to do phase noise test.
How much is the oscillator? more than 200USD?
about ADP150, I tried them before, it is similar to LP2985, but they are NOT the best voltage regulator. You can find the best regulator at Maxim-IC.
You can also build a regulator circult with Amplifier, it is much lower noise than ADP150
Noise is more important in the circuit,Crystek says their oscillator noise floor is -170dBc, if you use a bad LDO, you will be surprised.
Bypass capacitor of the ADP150 regulator should be more than 1uF, say 22uF. 1uF will not help on the noise.
Battery is good for noise. for some TCXOs and XO , I use battery for phase noise test. but for OCXO, I do not use battery because of the high current.
for 22.5792MHz, noise floor is -170dBc, if you use divider to get 11.2896Mhz, noise floor will be 6dBc worse at least.
you might neet to find good 11.2896MHz oscillator.
as I know, you can find 11.2896MHz SC-cut OCXO, phase noise= -125dBc/10Hz, and -170dBc/100KHz

P.S , oscillator phase noise is important in Audio system. you will hear the difference. good luck.
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Old 10th October 2011, 03:18 PM   #7
EUVL is offline EUVL  Europe
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Goldy,

Thanks for the link to the CN forum.
Interestng stuff.


Patrick
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Old 10th October 2011, 06:54 PM   #8
kimk is offline kimk  China
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GOLDY兄请往HIFIDIY收消息。。谢谢!
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Old 11th October 2011, 04:49 AM   #9
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Thanks for the reply Goldy - very helpful !

I have ordered two of the Crystek CCHD-957 to test - about HK$250 from Digikey - should arrive in a couple of weeks. I have emailed them to ask about power supplies for this xo but it seems they don't want to tell me. I have sent 4 emails so far and the replies from Luiz Orrichio (sales manager) have not given me any information at all, even after he has "spoken to the engineer responsible for the series". So I am starting to lose confidence in them, but of course, I will wait and see what the xo sounds like.

For the regulators, I have built my own using a maxim voltage reference but I think my skills are not good enough to get lower than a few uV of noise, so this is why I am trying IC regulators. I am using a AMB Sigma11 with a max6250 voltage reference - it works very well. Replace CR1 and D5 with the max6250 and add some extra capacitors as filters. I haven't tried removing one of the output mosfets yet - not sure of this would improve or worsen the performance.
Click the image to open in full size.

The old LM723 is very low noise so I'm also trying this (circuit shown above) for a cheap low noise source and after this I use a potential divider and a capacitance multiplier to create a lower noise 3.3V.

I have one more question - where can I buy sc cut tcxo/ocxo ? It seems that 10Mhz is easy to find but 12, 11.2, 22.4, 24.5 etc are hard to find, and too many fakes in this part of the world.

Thanks again for your help !

EDIT : Here's a Maxim paper on low noise regs
http://pdfserv.maxim-ic.com/en/an/AN3657.pdf

Last edited by KlipschKid; 11th October 2011 at 05:18 AM.
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Old 13th October 2011, 10:12 AM   #10
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Hi,

I checked the LP2985 - it uses a pnp pass transistor; the adp uses a pmos. I looked at the graphs for noise, regulation, etc, and the adp is much better than the LP2985. I have used a TPS79333 and this is similar to the LP2985, but neither are as good as the adp150. REG113 is another interesting reg - it uses dmos - but still it doesn't seem to perform as well as the adp.

http://www.national.com/ds/LP/LP2985.pdf
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