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Valve DAC from Linear Audio volume 13
Valve DAC from Linear Audio volume 13
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Old 15th September 2020, 12:49 PM   #871
agent.5 is offline agent.5  United States
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Quote:
Originally Posted by nautibuoy View Post
Interesting.

I've only had a quick look at your attacments and sorry if this has been covered before; I don't see any oscillators?

What sort of separation distance (i.e. Ethernet cable length) between the two boards are you envisaging?

Correction: Ah, I see, external oscillators via J10 & J11
I plan on getting a couple well tempered clocks from Andrea's group buy. It is looking likely to be two clocks, plus two frequency doublers, in 4 separate boxes. I read that LVDS can do long distance. See

https://www.ti.com/lit/an/slla127/slla127.pdf

But, all I really want is to separate the BBB maybe 500mm from the DAC.

Last edited by agent.5; 15th September 2020 at 12:51 PM.
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Old 15th September 2020, 12:52 PM   #872
nautibuoy is online now nautibuoy  United Kingdom
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'Sale' of the very last DAC PCB pending.
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Old 15th September 2020, 06:34 PM   #873
nautibuoy is online now nautibuoy  United Kingdom
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Originally Posted by agent.5 View Post
I read that LVDS can do long distance.
IIRC, Twisted Pear say their Teleporter has been tested over 30metres.

Will watch your development with interest.
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Old 15th September 2020, 09:48 PM   #874
agent.5 is offline agent.5  United States
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Thanks for your interest. I'm still making minor adjustments here and there. I will order boards, solder them. If it works, and I think it will, then I will post gerber and bom here, so others can play with it, if they want. As there is minimum quantity for a pcb order, and I really only need one set, I should have extra as well.
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Old 16th September 2020, 06:09 AM   #875
nautibuoy is online now nautibuoy  United Kingdom
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Quote:
Originally Posted by agent.5 View Post
I plan on getting a couple well tempered clocks from Andrea's group buy.
I started to check out Andrea's threads but they're in a really confused state and I haven't yet found a 'picture' of what is on offer with the various options. I assume you'll be using a 22/24MHz oscillator pair for the potential to use DSD512?
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Old 16th September 2020, 10:29 AM   #876
nautibuoy is online now nautibuoy  United Kingdom
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'Sale' of the very last DAC PCB pending.
The last PCB is still available.
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Old 16th September 2020, 01:15 PM   #877
agent.5 is offline agent.5  United States
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Originally Posted by nautibuoy View Post
I started to check out Andrea's threads but they're in a really confused state and I haven't yet found a 'picture' of what is on offer with the various options. I assume you'll be using a 22/24MHz oscillator pair for the potential to use DSD512?
more likely a 11MHz/12MHz Drixo PCB pair, plus 11MHz/12MHz SC cut crystals, plus a 11 to 22MHz and a separate 12 to 24MHz frequency doublers. The information is spread out over two separate threads, and they decided not to publish schematics. So, it is confusing.
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Old 16th September 2020, 04:12 PM   #878
MarcelvdG is offline MarcelvdG  Netherlands
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A construction with a frequency doubler could produce a spur at the second subharmonic of the 22.5792 MHz or 24.576 MHz clock, and if the DSD512 signal comes from a plain old single-bit sigma-delta, that could lead to artefacts due to mixing between the clock spur and the sigma-delta idle tone.

What level does the 11.2896 MHz or 12.288 MHz spur have compared to the 22.5792 MHz or 24.576 MHz? Can you say anything about what algorithm will generate the DSD512?

Last edited by MarcelvdG; 16th September 2020 at 04:19 PM.
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Old 16th September 2020, 05:42 PM   #879
agent.5 is offline agent.5  United States
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well, I have not seen the frequency doubler schematic, but it uses transformer. Andrea published some graphs

The Well Tempered Master Clock - Building a low phase noise/jitter crystal oscillator

I can ask questions over there.

This post lists options and there are too many. The frequency doubler requires transformer(s). Maybe something likes this

Low Phase Noise Design: Frequency Multipliers

But they decide not to publish schematic, so can't say for sure until I can see high res pictures.

Last edited by agent.5; 16th September 2020 at 05:51 PM.
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Old 16th September 2020, 05:56 PM   #880
nautibuoy is online now nautibuoy  United Kingdom
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Why not include the option for 'standard' NKD or Crystek oscillators on your board as an option - maybe pluggable boards like the twisted Pear Rheas? It would give upgrade options and might generate a wider interest?
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