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Cronus - It's about time.

Hi Folks,

You can find it here:
Cronus Reclocking

Cronus is a module designed for providing clocks to and reclocking output from digital sources. Cronus forms the backbone for audio sources built around 2 other module types - Hermes and Rhea.

Cronus was a long time coming - because we worked hard to make the results not just good - but superb. We could have released earlier - but we wanted to get in all of the things we desired after two prototypes.

Special thanks to Miero for his beta testing.

Extra special thanks to Brian for being patient with my long design process - and for putting together awesome beta and production kits.

Cronus provides the following:

  • An ultra low noise low impedance 3.3V power supply for clocks and reclocking section.
  • A clock selection multiplexer to switch between 44.1 and 48Khz time bases.
  • A selectable/bypassable ultra low phase noise clock divider to supply 1:2 or 1:4 clocks to a source.
  • A synchronous reclocker that re-clocks the audio from the source back to the master clock. This brings all signals back into alignment with the actual master clock regardless of source jitter - thus your final signal is as good as the clock you supply - which is to say - excellent!
  • Pads for pluggable clock sockets based on standard DIP(8 and 14) clock - See Rhea thread for more details.
  • An interface for connection to our isolation modules for various sources - See Hermes threads for more details. Hermes isolates your DAC completely from your source.
  • Interfaces for connecting to B3/B3SE and any other PCM/DSD DAC.
  • SMA and uFL connectors for external clock signals (both in or out)
  • uFL connectors for PCM/DSD output.

Some useful things to keep in mind:

The re-clocking section makes use of a Potato semi FlipFlop. When using a FF in this way the frequency of the clock input supplied to the FF must be at least 2 x any signal. For this reason ~22-24Mhz family clocks can be used for PCM signals up to 192Khz - for up to 384Khz you must double that. The device is capable of up to 768Khz PCM.

The module is designed for around ~5VDC input - but it is fine to go higher (absolute max is 16VDC) depending on the load you are putting on the VREG (adm7150) please refer to the datasheet about limits. The max current is listed at 800ma. The current consumption will vary depending on loads and audio frequencies. In testing using Crystek clocks (50Mhz family) I am drawing well under 150ma at 384khz. Keep in mind also that Hermes modules are designed to be powered on the clean side by the Cronus power supply.

The clocks are isolated from each-other and the rest of the circuit by utilizing L/C filtering with ferrites.

The Cronus is designed to work with Sources that provide a clock selection signal (CS) and can accept an external audio master clock - it is currently tested with two Hermes modules. Hermes-BBB for the BeagleBone black (using Botic distro), and the Hermes-Amanero for the Amanero USB module. There will be a thread for each. Both are tested and work up to 384Khz.

I will fill in more details to this post as necessary.

A manual is under way for each module - but I hope you basically know what you need right now. :)

The Hermes and Rhea threads will fill in a lot more detail.

I have also attached the pinouts of the .1" headers on the output side of the cronus and the Hermes header.

Note: If you use the terminal blocks - it is recommended to mount them on the bottom side so they don't interfere with uFL connectors etc.

Ask away!
 

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Last edited by a moderator:
Russ, you probably missed my question as I slipped it into an edit, but I was wondering about the disadvantages of the faster clocks. Slightly increased noise/power consumption?

You can easily experiment with both. I have found the 50Mhz range clocks to work very very well. And when used to synch clock the B3/B3SE you can go up to 384khz.

The 50Mhz range is the most flexible - you will typically get somewhat lower phase noise with lower freq clocks. With good 40-50mhz clocks its already low enough to get superb results.

You will be fine either way.
 
1. Can the chosen clock be effectively used to synchronize a secondary device, as well as provide base clocks to the primary device (in this case, remove clock drift between the BBB clock and an input device, whose clock could be surgically replaced)?

2. Are there any general downsides, other than maximum sample rate, to slower clocks, like the 22-24MHz, and 11-12MHz?
 
1. Can the chosen clock be effectively used to synchronize a secondary device, as well as provide base clocks to the primary device (in this case, remove clock drift between the BBB clock and an input device, whose clock could be surgically replaced)?

2. Are there any general downsides, other than maximum sample rate, to slower clocks, like the 22-24MHz, and 11-12MHz?

1. The idea is you have exactly one authoritative clock base. :) Yes. The source uses it to derive it's stream - and Cronus makes certain that in the end the signals are all finally aligned and sent to the DAC. You would not want to have two clock domains except in the case where you are doing ASRC as you can do with the ES9018 etc.

2. None. They will work great! That is precisely why we make clock options so easy.

Cheers!
Russ
 
Hi Russ,
I got little lost on which module I will need to use on my BBB + Dac (with I2S input).
Do I need all of the followings:
Hermes-BBB Isolator Module
Cronus re-clocking + Rhea

If I also want to use USB input via Amenero together with BBB, Will I need another Hermes-AmeneroUSB Isolator Module ? Will I have 2 Hermes connected to the Cronus ?
Any example connection diagram available?

Also How do I choose between these 2 options :

Cronus Re-clocking Module with 45.1584/49.152MHz Rhea Pair
Cronus Re-clocking Module with 22.5792/24.576MHz Rhea Pair

Thanks
 
@syklab

You will most likely want the combo - Cronus Re-clocking Module with 45.1584/49.152MHz Rhea Pair + the Hermes-BBB It just depends on the max sample rate you think you will use. For up to 192Khz you can do the 22.5792/24.576MHz. You need the 45.1584/49.152MHz clocks for up to 384khz. :)

You can also get the Hermes-Amanero but you can't use both hermes at the same time - but you can easily switch back and forth.

More information will be presented in the Hermes threads.

If there is demand we could easily produce a 2:1 multiplexer for connecting two Hermes modules to a single Cronus. Or you could actually use 2 Otto-II right now. :)
 
If there is demand we could easily produce a 2:1 multiplexer for connecting two Hermes modules to a single Cronus. Or you could actually use 2 Otto-II right now. :)

I guess there will be demand for such a module!
And even for a 4:1 multiplexer :D
I can easily imagine a dac with:
- An embedded network player such as BBB
- An amanero for external usb connectivity
- A spdif => i2s module
- An external LVDS i2s connector (hdmi or RJ45) input such as TPA teleporter.

If one want to build a flexible synchonous ES9018 dac, such a module nearly mandatory. ;)
 
Hi Folks,

You can find it here:
Cronus Reclocking
-snip-

Ask away!

Thank you for this info and congratulation on your great works. I'm very happy to have this occasion of ordering these items at last.

BTW, how do you pronounce Hermes? Simply in an English way or somewhat in a French way like a luxurious brand, or even in a way back to the ancient Greek?

I know the question is silly but couldn't resist to ask :D.

twluke