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ο1 precision master clock development

omicron1: A low-jitter, low phase noise clock generator for upgrading digital audio devices

ο1 precision master clock development

Postby amb » November 8th, 2016, 2:22 pm

Last update: November 25, 2016
Status: PCBs now released and available at AMB audio shop. Official website is now up.

Background

As outlined in the Other DCX2496 mods thread, I was looking to develop a simple but effective master clock upgrade for the Behringer DCX2496, DCX2496LE and DEQ2496. That effort resulted in a circuit described in that thread using an Analog Devices ADM7150ARDZ-3.3 ultra low noise and high PSRR local voltage regulator, powering a low jitter and phase noise Crystek CCHD-957-25-24.576 oscillator. It's basically the same thing taken from the γ3 DAC (actually, the γ24 DAC core), except there is no clock buffer, because the oscillator(s) will drive only one load.

I then realized that the circuit could be generalized to make it useful as an upgrade for many other digital audio devices, such as CD players, digital streamers, DACs and ADCs. Some of these need only a single master clock frequency whereas others need two, to support multiples of 44.1KHz and 48KHz sample rates.

I am calling this new circuit ο1 ("omicron 1").

Circuit details

See the schematic diagram below. There is a 3P Molex header providing connections to a DC power source and ground.

Starting with the ADM7150 + CCHD-957 circuit, I added the option of a second oscillator and the ability to select between the two. This is accomplished with the SEL pin on the 3P header. A logic "high" enables oscillator X1 and disables X2. A logic "low" does the opposite. For this control signal, resistors R3 and R4 perform logic level attenuation from 5V to 3.3V if needed. Otherwise, R3 can be shorted and R4 omitted.

If only one master clock frequency is needed (as in the case of the Behringer DCX2496, DCX2496LE and DEQ2496), then everything enclosed by the dashed line box should be omitted. The SEL pin will have no function and X1 will be enabled by default.

The CCHD-957 has a form factor of 14x9mm. Since it's only available in a few frequencies, 7x5mm pads are also included to broaden the usable oscillator types in order to make the circuit usable in more devices. The Fox Xpresso FXO-HC736R series 7x5mm oscillators as used in the γ1.5 are good alternatives.

Some devices need 3.3V logic level clocks whereas others need 5V. The CCHD-957 and FXO-HC736R series are 3.3V-only, but there are other 5V oscillators that fit the 14x9mm or 7x5mm form factors. This highlights the need to make the circuit support a variety of oscillators.

For 3.3V master clock, the VCC input should be 5V-15V, U1 should be ADM7150ARDZ-3.3, and the oscillators should be 3.3V types.

For 5V master clock, VCC should be 6-15V, U1 should be ADM7150ARDZ-5.0, and 5V oscillators should be used.

The master clock output is via a Hirose U.FL coaxial connector and shielded cable, excellent for high frequency transmissions (rated to 6GB).

The PCB is small at 1.5" x 1.0", with one single a mounting hole. There is soldermask and silkscreen on both sides. It should be easy to fit the ο1 into equipment with some interior space. The board is all-SMD except the 3P header. Nothing should be too small to hand-solder. The smallest passive parts are 0805, others are between 1206 oand 1210. U1 is SOIC-8, U2 is SOT-23, and the oscillators should all be relatively easy to solder.

PCB top view:
Image

PCB bottom view:
Image

Schematic diagram:
Image

Parts list

Please refer to the official ο1 website for the most up to date information, including the parts list and instructions.

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Re: ο1 precision master clock development

Postby Balcmeg » November 8th, 2016, 11:28 pm

What is the estimated build cost as it is now? These reclock cost a lot to buy normally. You could destroy a whole business ;)


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Re: ο1 precision master clock development

Postby amb » November 9th, 2016, 12:52 am

The Crystek CCHD-957 oscillators are about USD $25 each, but you only need one if the original master clock you're upgrading requires only one frequency. Other oscillators are much cheaper. For example, the Fox Xpresso are only $1.50 each but perform very well (if not quite as good as the CCHD-957). The ADM7150 voltage regulator is about $8, and the rest of the parts are inexpensive.
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Re: ο1 precision master clock development

Postby Balcmeg » November 9th, 2016, 1:04 am

About what I assumed - an interesting project for sure. Might be interested to try one in my cd transport instead of the current one that's quite large. Good price as well, this should end up several times below other precision clocks on the market.


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Re: ο1 precision master clock development

Postby whomper » November 9th, 2016, 2:37 am

Looking forward for this!

Are there recommended part numbers for a single Osc version? Have an opportunity to order some parts and would like to make sure this is part of the order (otherwise shipping cost to Israel are insane).
κDC2496, γ1.5, γ2, γ3, α10 (α24 based), balanced β22, 2 x β24, M³, Grado ES2E, GS2000E, AGK K700, CBT36 Speakers
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Re: ο1 precision master clock development

Postby amb » November 9th, 2016, 2:45 am

I'm working on the BOM and will update the first post above very soon.

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Re: ο1 precision master clock development

Postby poseidonsvoice » November 9th, 2016, 3:40 am

Like I said before, I'm in! The cost is immaterial but the level of engineering is material!

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Re: ο1 precision master clock development

Postby amb » November 10th, 2016, 3:47 am

The first post now has a parts list with vendor stock numbers. FYI.
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ο1 prototype pcb ordered

Postby amb » November 11th, 2016, 11:37 pm

I ordered 10 pcs. of ο1 PCBs for prototyping purposes. Since the board is relatively simple (and passes netlist and DRC checks), I don't ecpect to find an error in there. The final release version will probably be identical.

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Re: ο1 precision master clock development

Postby poseidonsvoice » November 12th, 2016, 9:10 am

Let me know when you are ready to sell or if I can prepay that would be grand.

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