I'm looking for a multifrequency clock for my A/D converter (described in another thread).
I currently use a standard 12.288MHz xtal oscillator, but I need something that can generate all the standard frequencies (8.192, 11.2896, 12.288, 24.576 etc.) so I can record at difference samplerates.
Has anybody here made a circuit for that purpose?
This BB chip looks interesting:
http://focus.ti.com/docs/prod/folders/print/pll1700.html
Has anybody tried it?
Best regards,
Mikkel C. Simonsen
I currently use a standard 12.288MHz xtal oscillator, but I need something that can generate all the standard frequencies (8.192, 11.2896, 12.288, 24.576 etc.) so I can record at difference samplerates.
Has anybody here made a circuit for that purpose?
This BB chip looks interesting:
http://focus.ti.com/docs/prod/folders/print/pll1700.html
Has anybody tried it?
Best regards,
Mikkel C. Simonsen
Re: Re: Multi-frequency clock
It looks interesting - but I think a bit too complicated for this purpose... As long as I use the A/D for recording, does the jitter matter? The data goes directly into a FIFO and on to a harddrive anyway...
But perhaps I should try one of your clocks in my CD-player
[EDIT]I just realised that the jitter probably does matter - but how much? Perhaps I should use a "good" clock for the main frequency, and a simple one for the rest...
BTW, how do you "distribute" the clock? I will need a clock for the A/D, the D/A and the playback circuit. Do you simply connect the loads in parallel, or do you need some kind of buffer?[/EDIT]
Best regards,
Mikkel C. Simonsen
Elso Kwak said:Hi Mikkel,
You can use my clock that is the KWAK-CLOCK, connect all outputs together and enable each frequency with the Latch of the comparator. So for the four frequencies listed you will need four clocks.
The PLL1700 has too much jitter I believe.
It looks interesting - but I think a bit too complicated for this purpose... As long as I use the A/D for recording, does the jitter matter? The data goes directly into a FIFO and on to a harddrive anyway...
But perhaps I should try one of your clocks in my CD-player
[EDIT]I just realised that the jitter probably does matter - but how much? Perhaps I should use a "good" clock for the main frequency, and a simple one for the rest...
BTW, how do you "distribute" the clock? I will need a clock for the A/D, the D/A and the playback circuit. Do you simply connect the loads in parallel, or do you need some kind of buffer?[/EDIT]
Best regards,
Mikkel C. Simonsen
Re: Re: Re: Multi-frequency clock
mcs said:
Less than what?
The PLL1700 chip only costs $2...
Best regards,
-----------------------------------------------------
When you add up the cost of high quality components, ancilliaries, power supply, enclosure, plus the amount of time in development and testing, it is cheaper to spend 200 euros as you can spend the time doing something alse!
Re: Re: Re: Multi-frequency clock
The PLL1700 is ok.
For better jitter numbers I suggest SM8706, SM8707 (used in better DVD players for example.
But to be honest, reading all these questions on very basic issues, you might seriously want to consider the solution FMAK posed in stead of doing something that might be over your head
The PLL1700 is ok.
For better jitter numbers I suggest SM8706, SM8707 (used in better DVD players for example.
mcs said:
But to be honest, reading all these questions on very basic issues, you might seriously want to consider the solution FMAK posed in stead of doing something that might be over your head
Re: Re: Multi-frequency clock
The problem with this solution is that the WD8 is designed to drive a complete device as opposed to individual chips. The OP's ADC still has to have an internal clock system capable of locking to an external clock. That usually means a VCXO or two and a PLL.
ray.
fmak said:
The problem with this solution is that the WD8 is designed to drive a complete device as opposed to individual chips. The OP's ADC still has to have an internal clock system capable of locking to an external clock. That usually means a VCXO or two and a PLL.
ray.
Re: Re: Re: Re: Multi-frequency clock
Best regards,
Mikkel C. Simonsen
It doesn't look like they have the features I need. I need a clock generator that can be switched between 32, 44.1, 48, 88.2 and 96kHz. The only NPC chip that has those features seems to be the SM8701. It still has better specs than the PLL1700 (150ps vs. 150/300ps jitter), but unfortunately it's still a lot worse than the 40-70ps of the chips you mentioned. Where can you buy the NPC chips in Europe?rbroer said:
I can easily make a circuit that works - but I don't know how to make the circuit as good as possible. Why not tell me where to get more information on the subject instead of telling me I'm stupid? I know I'm stupid, but I'm willing to learnBut to be honest, reading all these questions on very basic issues, you might seriously want to consider the solution FMAK posed in stead of doing something that might be over your head
Best regards,
Mikkel C. Simonsen
Re: Re: Re: Re: Multi-frequency clock
Development time and testing? Isn't this diyAudio.com? Would I be spending time here if I wanted to buy my equipment?
I also haven't seen the project I'm working on for sale anywhere (not at a price I can afford at least)...
Best regards,
Mikkel C. Simonsen
Since I need the clock for a project, I have to pay for the power supply and enclosure anyway. And high quality components certainly cost nowhere near 200 euros.fmak said:When you add up the cost of high quality components, ancilliaries, power supply, enclosure, plus the amount of time in development and testing, it is cheaper to spend 200 euros as you can spend the time doing something alse!
Development time and testing? Isn't this diyAudio.com? Would I be spending time here if I wanted to buy my equipment?
I also haven't seen the project I'm working on for sale anywhere (not at a price I can afford at least)...
Best regards,
Mikkel C. Simonsen
I don't recall anybody calling you stupid Mikkel
Why don't you look into the PLL1707, PLL1708.
These babies seem to be able to output all frequencies you want and more and have better jitter specs as well.
Now I like to use GOOGLE and the DIYAUDIO search option.
There's a wealth of info out there, just sometimes you need to spend a little time.
Happy DIY.
Why don't you look into the PLL1707, PLL1708.
These babies seem to be able to output all frequencies you want and more
and have better jitter specs as well.Now I like to use GOOGLE and the DIYAUDIO search option.
There's a wealth of info out there, just sometimes you need to spend a little time.
Happy DIY.
No, not directlyrbroer said:I don't recall anybody calling you stupid Mikkel
Don't take it too seriously...Yes, they do look a lot better. I think I "disqualified" them because of the 3.3V supply initially, but the specs are a lot better. Perhaps I should include a 3.3V regulator in my circuit...Why don't you look into the PLL1707, PLL1708.
These babies seem to be able to output all frequencies you want and more
I do also, but it's sometimes difficult to find what you're looking for. I often find interesting stuff when I was looking for something elseNow I like to use GOOGLE and the DIYAUDIO search option.
There's a wealth of info out there, just sometimes you need to spend a little time.
Best regards,
Mikkel C. Simonsen
I had a look at the PLL1708, and this is what I came up with: Schematic
Does it look reasonable?
The 117 needed ceramic power decoupling caps are not shown on the schematic to keep it simple...
The datasheet recommends buffering the clock outputs, and also keeping them seperate. To keep the different outputs seperate I guess using single inverter chips (like the SN74AHCT1G04DBVR - a nice short name) would be a good idea, instead of using the normal "six-packs"...
Best regards,
Mikkel C. Simonsen
Does it look reasonable?
The 117 needed ceramic power decoupling caps are not shown on the schematic to keep it simple...
The datasheet recommends buffering the clock outputs, and also keeping them seperate. To keep the different outputs seperate I guess using single inverter chips (like the SN74AHCT1G04DBVR - a nice short name
) would be a good idea, instead of using the normal "six-packs"...Best regards,
Mikkel C. Simonsen
clock noise at the ADC is the worst situation, it cannot be "fixed" by any amount of after the fact processing
any frequency multipler pll scheme is going to increase jitter
considering the 2 points above in light of the truely awsome DSP capacity of modern PCs i couldn't imagine not using a single low noise clock, 96K sample rate and, if other output data rates are required, just resampling after aquisition in a PC
any frequency multipler pll scheme is going to increase jitter
considering the 2 points above in light of the truely awsome DSP capacity of modern PCs i couldn't imagine not using a single low noise clock, 96K sample rate and, if other output data rates are required, just resampling after aquisition in a PC
I know PLLs are "evil" etc. But for the moment I'm trying to make good and flexible recorder. I might want to record 4 channels at 44.1khz rather than 2 channels at 96kHz etc. And that is a lot easier with a programmable clock.
And my current main goals are a reliable circuit, and good (not great) quality. I want something that's better than a cheap casette deck or Minidisc, and I think that's possible even with a PLL clock. Once I have a stable, working circuit I can try experimenting with better clock sources...
So I would really like to know if my circuit is likely to work (I think it should), and if there are any changes I should do to make it better.
Best regards,
Mikkel C. Simonsen
And my current main goals are a reliable circuit, and good (not great) quality. I want something that's better than a cheap casette deck or Minidisc, and I think that's possible even with a PLL clock. Once I have a stable, working circuit I can try experimenting with better clock sources...
So I would really like to know if my circuit is likely to work (I think it should), and if there are any changes I should do to make it better.
Best regards,
Mikkel C. Simonsen
as a diyer you are your own customer and designer so you can balance requirements, quality and complexity for yourself
but in your reply you have refined the "flexible sample rate" feature to actually being about a channel/storage bandwidth tradeoff - why not clarify this in your own mind with the engineering tradeoff between a good quality single clock for 96KHz and single 74AC74 flip-flop divide by 2 for 48 K 4 channel operation vs the increased engineering complexity and lower quality of a pll multiplier scheme
but in your reply you have refined the "flexible sample rate" feature to actually being about a channel/storage bandwidth tradeoff - why not clarify this in your own mind with the engineering tradeoff between a good quality single clock for 96KHz and single 74AC74 flip-flop divide by 2 for 48 K 4 channel operation vs the increased engineering complexity and lower quality of a pll multiplier scheme
When I figure out what clocks I actually need, two good (Kwak/LC/etc) clocks and a flip-flop divider could be a good solution... But for now the PLL1708 seems to be the least complex option.
And the clock circuit isn't that complex compared to the 18-chip mainboard...
Best regards,
Mikkel C. Simonsen
And the clock circuit isn't that complex compared to the 18-chip mainboard...
Best regards,
Mikkel C. Simonsen
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