I haven't made any measurements but I image that of forward biased PN-junction is much quiter than a reversed.
A LED has charateristics similar for a diode of pure silicone. The only difference is a factor in the EXP() function. If you want low leakage at a higher level, LED's works fine if they have a black hat! Light will create photo currents.
The disadvantage of diodes or LED's are rather high temperature coeffcient, 0,3 %/degree and similar for LED's (don't remember the exact value). They are also dependent of process techology, especially LED's! 1.5 - 1.9 V (with same current) are normal distributions (my experience). "Bad" LED's have usually higher voltage and it comes from the "resistive" part, higher losses.
When we talk dynamic impedance diodes are rather poor compared to a simple LM431 or similar. We talk of a factor of 20-50! LM431 has 0,5-1 ohms and a diode has 25 ohms at 1 mA.
A LED has charateristics similar for a diode of pure silicone. The only difference is a factor in the EXP() function. If you want low leakage at a higher level, LED's works fine if they have a black hat! Light will create photo currents.
The disadvantage of diodes or LED's are rather high temperature coeffcient, 0,3 %/degree and similar for LED's (don't remember the exact value). They are also dependent of process techology, especially LED's! 1.5 - 1.9 V (with same current) are normal distributions (my experience). "Bad" LED's have usually higher voltage and it comes from the "resistive" part, higher losses.
When we talk dynamic impedance diodes are rather poor compared to a simple LM431 or similar. We talk of a factor of 20-50! LM431 has 0,5-1 ohms and a diode has 25 ohms at 1 mA.
Herr Per:
Looks like a Colpitts, works more like a Butler. The signal passes
through the crystal, to remove harmonics and noise sidebands. So it is operating close to the series resosant point. Possible it is just above that point a bit. You can also tune a Butler to operate close (but not exactly) to the series point with a parallel mode crystal.
You can verify series mode by building one with a LC tank, and seeing which one works: series or parallel. It has to be close to series, otherwise the signal at the resistor where the signal is picked off will be too small to use.
Bulters work fine too. This one has the advantage of one less active device. Big deal, eh?
Jocko
Looks like a Colpitts, works more like a Butler. The signal passes
through the crystal, to remove harmonics and noise sidebands. So it is operating close to the series resosant point. Possible it is just above that point a bit. You can also tune a Butler to operate close (but not exactly) to the series point with a parallel mode crystal.
You can verify series mode by building one with a LC tank, and seeing which one works: series or parallel. It has to be close to series, otherwise the signal at the resistor where the signal is picked off will be too small to use.
Bulters work fine too. This one has the advantage of one less active device. Big deal, eh?
Jocko
Jocko Homo said:
This is true but the main thing (for digital purposes) is jitter and phase noise. Harmonics are ADDED if you convert the sinus wave into square wave.
You still use the "L" in the crystal and as I said before you get much lower Q when you tune and low Q is bad if you talk phase noise. You must have a crystal for series mode if you want good results.
The resistor serves as a shunt. You measure the current through the crystal, still the big "L" instead of the low "R".
You still need at least three active devices to be able to use the signal.
I wonder how these high precision oscillators are designed. Anyone who has a schematic over these metal cans (100 USD and above)?
Jitter and phase noise are caused by noise sidebands.
As I recall.........someone complained that making an quality oscillator was not that easy and one of the problems was radiation from a board that is a few inches above the main PCB. This one has no harmonics. The circuit that converts it (read the filter chip in most CD players) is on the board. You can drive them with a sine wave of sufficient level.
The resistor is not a shunt. Ever measure the series R of a crystal??
Jocko
As I recall.........someone complained that making an quality oscillator was not that easy and one of the problems was radiation from a board that is a few inches above the main PCB. This one has no harmonics. The circuit that converts it (read the filter chip in most CD players) is on the board. You can drive them with a sine wave of sufficient level.
The resistor is not a shunt. Ever measure the series R of a crystal??
Jocko
This topic was very narrow, a dialogue between me and Jocko Homo only. Maybe this is a signal of the nature of crystal oscillators?
My contribution was to lift forward the Butler oscillator as an alternative the common Colpitts. A Buttler oscillator is not an alternative for most people since it requires special crystal (series resonance is rather unusual these days).
Still, I'm very interested in how a precision oscillator is made (those in a rather large metal can).
My contribution was to lift forward the Butler oscillator as an alternative the common Colpitts. A Buttler oscillator is not an alternative for most people since it requires special crystal (series resonance is rather unusual these days).
Still, I'm very interested in how a precision oscillator is made (those in a rather large metal can).
If you are refering to the large ovenized ones, you might find some info at www.bliley.com .Those types use a special crystal cut, usually in the 5-10 MHz range, as that is where the "sweet spot" for stability is.
Jocko
Jocko
I'm interested in the design
http://www.minicircuits.com/application.html
You could always go buy some or get some samples and cut them open and reverse engineer them.
http://www.google.com/search?hl=en&ie=UTF8&oe=UTF8&q=crystal+oscilltors&btnG=Google+Search
Show some inititive and do a little research. You are delving into a topic that requires much more than a few paragraphs for an answer. Your questions could be more specific. "I am interested in ......" doesn't help a reader to figure out what you really to know.
H.H.
http://www.minicircuits.com/application.html
You could always go buy some or get some samples and cut them open and reverse engineer them.
http://www.google.com/search?hl=en&ie=UTF8&oe=UTF8&q=crystal+oscilltors&btnG=Google+Search
Show some inititive and do a little research. You are delving into a topic that requires much more than a few paragraphs for an answer. Your questions could be more specific. "I am interested in ......" doesn't help a reader to figure out what you really to know.
H.H.
Once again, HarryHaller, try to be nice!
We are a couple of thousand people here and I believe some of us do really know what others ask. You know and I know, it can be hard to really find anything out there on the net. Many sites are batabase based and therefore often hard to search in from external search engines. If a topic is too big noone will answer and is it NOT too big I gather some of us bother to answer.
My question here at the bottom was very simple: Does anyone know whats inside a crystal oscillator of a finer model?
I asked in a other place about folded cascodes and got excellent answers from a person who really bother to find it even though he himself didn't know (all of it?). Let us continue in the same spirit as mlloyd1 and others.
Thanks to you, mlloyd1!
We are a couple of thousand people here and I believe some of us do really know what others ask. You know and I know, it can be hard to really find anything out there on the net. Many sites are batabase based and therefore often hard to search in from external search engines. If a topic is too big noone will answer and is it NOT too big I gather some of us bother to answer.
My question here at the bottom was very simple: Does anyone know whats inside a crystal oscillator of a finer model?
I asked in a other place about folded cascodes and got excellent answers from a person who really bother to find it even though he himself didn't know (all of it?). Let us continue in the same spirit as mlloyd1 and others.
Thanks to you, mlloyd1!
Crystal Oscillator Circuits
Hi per-Anders,
To put it mildy: my experience with crystal oscillators has been extremely checkered and frustrating.
I have built various circuits from the application notes of TCXO and other cantype oscillators manufacturers. Quite often the circuit does not work at all or oscillates at a totally wrong frequency. This is particularly true for the overtone oscillators that use the crystal at the third or fifth overtone. Your example of the Euroquartz application note was a example of a collection of bad hints.
My strong impression is that cantype oscillator manufactures don't want let us know what is inside the can....
I once opened a cheap 10MHz one and found a 74HC04 in SMT.....
Well nothing to learn there.
Also frustrating is trying to order samples or just to buy low jitter crystal oscillators. I tried to order a 125 MHz Viteonline SMT crumb, after I eased myself that a +3V supply was OK, but the stupid website yelled at me that my emailaddress is invalid. How to invalid. I receive 10 emails per day.
The whole subject of crystal oscillators is full of black magic, contradictory statements and hilarious jitter specs. Some say you need minimal drive for a overtone crystal others say just the opposite. Crystals are also different if they come from a other manufacturer. Specifications are aften difficult to get. For some frequencies you have the choice between fundamental and third overtone . But it is not printed on the crystal.
I was curious what component values you use for your clock. Which one I should ask is THE Sjostrom-clock. If you have a working solution I strongly suggest to take notes and keep it for future reference.
My most weird experience is that a 100MHz fifth overtone crystal gives a better sound than a 99 MHz third overtone crystal in my asynchronous reclocker. But both don't oscillate at the desired frequency.
Well good luck.
Hi per-Anders,
To put it mildy: my experience with crystal oscillators has been extremely checkered and frustrating.
I have built various circuits from the application notes of TCXO and other cantype oscillators manufacturers. Quite often the circuit does not work at all or oscillates at a totally wrong frequency. This is particularly true for the overtone oscillators that use the crystal at the third or fifth overtone. Your example of the Euroquartz application note was a example of a collection of bad hints.
My strong impression is that cantype oscillator manufactures don't want let us know what is inside the can....
I once opened a cheap 10MHz one and found a 74HC04 in SMT.....
Well nothing to learn there.
Also frustrating is trying to order samples or just to buy low jitter crystal oscillators. I tried to order a 125 MHz Viteonline SMT crumb, after I eased myself that a +3V supply was OK, but the stupid website yelled at me that my emailaddress is invalid. How to invalid. I receive 10 emails per day.
The whole subject of crystal oscillators is full of black magic, contradictory statements and hilarious jitter specs. Some say you need minimal drive for a overtone crystal others say just the opposite. Crystals are also different if they come from a other manufacturer. Specifications are aften difficult to get. For some frequencies you have the choice between fundamental and third overtone . But it is not printed on the crystal.
I was curious what component values you use for your clock. Which one I should ask is THE Sjostrom-clock. If you have a working solution I strongly suggest to take notes and keep it for future reference.
My most weird experience is that a 100MHz fifth overtone crystal gives a better sound than a 99 MHz third overtone crystal in my asynchronous reclocker. But both don't oscillate at the desired frequency.
Well good luck.
Hi Elso, nice to have you back.
Funny, but your post title is the exact title of a nice book by Robert Matthys, which I found quite interesting. It provides lots of info on the working principles of the XOs, and a lot of practical circuits and descriptions as well. A must have From this book, I've tested almost all the discrete and IC-base XOs (at least the ones Matthys defined from fair to excellent). Can't comment on the "audio" properties of all XOs I built from this book, but all worked immediately and at the right frequency.
This one (a "Matthysian" one too) I built with a 5th overtone 98.304MHz crystal I ordered from Klove (www.klove.nl) and measured 98.30406MHz after 1 hour... Maybe I'm just lucky
Funny, but your post title is the exact title of a nice book by Robert Matthys, which I found quite interesting. It provides lots of info on the working principles of the XOs, and a lot of practical circuits and descriptions as well. A must have
From this book, I've tested almost all the discrete and IC-base XOs (at least the ones Matthys defined from fair to excellent). Can't comment on the "audio" properties of all XOs I built from this book, but all worked immediately and at the right frequency.This one (a "Matthysian" one too) I built with a 5th overtone 98.304MHz crystal I ordered from Klove (www.klove.nl) and measured 98.30406MHz after 1 hour... Maybe I'm just lucky
Crystal Oscilator Circuits
Hi/Bonjour Francois,
Looks like I need to buy the book by Matthys.
The <B>AUDIO</B> properties of the oscillators are the most important properties for me. That' s why I wanted to build a Collpitts 100MHz oscillator. Did you find a example in the book by Matthys?
Lifting a circuit from the book and build it is of course something different from what am doing trying to build a new oscillator circuit with a FET.
May I sent you my overtone circuit for comment? It does improve the sound a lot with the asynchronous reclocker.
Hi/Bonjour Francois,
Looks like I need to buy the book by Matthys.
The <B>AUDIO</B> properties of the oscillators are the most important properties for me. That' s why I wanted to build a Collpitts 100MHz oscillator. Did you find a example in the book by Matthys?
Lifting a circuit from the book and build it is of course something different from what am doing trying to build a new oscillator circuit with a FET.
May I sent you my overtone circuit for comment? It does improve the sound a lot with the asynchronous reclocker.
Hi Elso,
First, no there's no Colpitt above 20 MHz in the book This configuration is said to have poor to fair performances and is not investigated at higher frequencies. According to Matthys, its sensivity to power supplies and stability is not that good, but he doesn't account for audio performances... Matthys mainly classifies XOs with respect to the waveform at crystal, in-circuit Q, and short term stability, this latter being a nice indication of the jitter performances of the XO.
And, yes, I agree, building an XO straight from a book's schematics is not a revolutionary work, but I had so numerous desillusions (mainly with overtone ones) with all the circuits I found on the web that I wanted to start with something working
The one I linked in my previous post gave the best audio results (amongst the three I tried) in asynchronous reclocking (incidentally it was rated as outstanding by Matthys ), but I will try to improve it with different options (BJT type, power supply, etc...). And of course, I would be happy to comment your overtone circuit, if I dare to . Thanks a lot.
First, no there's no Colpitt above 20 MHz in the book
This configuration is said to have poor to fair performances and is not investigated at higher frequencies. According to Matthys, its sensivity to power supplies and stability is not that good, but he doesn't account for audio performances... Matthys mainly classifies XOs with respect to the waveform at crystal, in-circuit Q, and short term stability, this latter being a nice indication of the jitter performances of the XO. And, yes, I agree, building an XO straight from a book's schematics is not a revolutionary work, but I had so numerous desillusions (mainly with overtone ones) with all the circuits I found on the web that I wanted to start with something working
The one I linked in my previous post gave the best audio results (amongst the three I tried) in asynchronous reclocking (incidentally it was rated as outstanding by Matthys
), but I will try to improve it with different options (BJT type, power supply, etc...). And of course, I would be happy to comment your overtone circuit, if I dare to . Thanks a lot.Francois,
have you also started experimenting with asynchronous reclocking? What are your impressions? Do you have any theory why it might be appealing?
I have not tried because
a) from a theoretical point, I would expect it to sound ghastly
b) I currently have no multibit DAC in operation (which may change soon)
Regards,
Eric
have you also started experimenting with asynchronous reclocking? What are your impressions? Do you have any theory why it might be appealing?
I have not tried because
a) from a theoretical point, I would expect it to sound ghastly
b) I currently have no multibit DAC in operation (which may change soon)
Regards,
Eric
Hi Eric
Yes, I've done some tests with asynchronous reclocking. I experimented it with a 98MHz clock on my old PCM63-based DAC. And it works
Subjective impressions are a more analogue sound, less listening fatigue (if any), less harshness.
But don't ask me why I haven't got a clue I haven't gone too far (as Elso did), like comparing various frequencies and XO types. This will be next step. But it was a simple mod to my DAC, and I couldn't resist to test it, even with the huge lack of theoretical background.
Give it a try
Yes, I've done some tests with asynchronous reclocking. I experimented it with a 98MHz clock on my old PCM63-based DAC. And it works
Subjective impressions are a more analogue sound, less listening fatigue (if any), less harshness.
But don't ask me why
I haven't got a clue I haven't gone too far (as Elso did), like comparing various frequencies and XO types. This will be next step. But it was a simple mod to my DAC, and I couldn't resist to test it, even with the huge lack of theoretical background. Give it a try
Overtone Crystal Oscillators
Bonjour/Hi Francois,
Currently I am using a modified Colpittsoscilator with a 100 MHz off the shelve fifth overtone crystal in the asynchronous reclocker. Actually it is running at about 66 MHz. It also works with a one transistor Butleroscillator, same frequency; slightly higher output. Also tried a Pierce type oscillator from www.qsl.net/g3pho/13cm.htm . Same frequency, sound quality output not as good as the first two tried. Probably the most elegant solution is to find a <B><i>inverted mesa technology fundamental mode </B></I>100 MHz crystal.
Thus far I have found two firms on the net: Connor-Winfield and www.hy-q.co.uk No reply from my emails yet. Anyone has a alternative source for these type of crystals or any experience???
Francois, I can corroborate your findings: more analogue like sound, less harshness, less listener fatigue, better bass.
Capslock/Eic, I can feel with you as I just got a Tek 485 from Ebay.de with a rotten TIME DIV switch in the audio region. But I can look at the waveform coming from the oscillator. A theoretical explanation for the asynchronous reclocking might be to look at it as a resampling method.
Bonjour/Hi Francois,
Currently I am using a modified Colpittsoscilator with a 100 MHz off the shelve fifth overtone crystal in the asynchronous reclocker. Actually it is running at about 66 MHz. It also works with a one transistor Butleroscillator, same frequency; slightly higher output. Also tried a Pierce type oscillator from www.qsl.net/g3pho/13cm.htm . Same frequency, sound quality output not as good as the first two tried. Probably the most elegant solution is to find a <B><i>inverted mesa technology fundamental mode </B></I>100 MHz crystal.
Thus far I have found two firms on the net: Connor-Winfield and www.hy-q.co.uk No reply from my emails yet. Anyone has a alternative source for these type of crystals or any experience???
Francois, I can corroborate your findings: more analogue like sound, less harshness, less listener fatigue, better bass.
Capslock/Eic, I can feel with you as I just got a Tek 485 from Ebay.de with a rotten TIME DIV switch in the audio region. But I can look at the waveform coming from the oscillator. A theoretical explanation for the asynchronous reclocking might be to look at it as a resampling method.
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