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

[gabor80]

Sorry to say but the 45Mhz board has very same problem. Sometime it starts the good 45Mhz sometimes 49.182 Mhz. But in tis case it is not changed when I touched the base with sold. iron, It starts 45 or 49 Mhz randomly...

[andrea_mori]

Originally Posted by gabor80

Sorry to say but the 45Mhz board has very same problem. Sometime it starts the good 45Mhz sometimes 49.182 Mhz. But in tis case it is not changed when I touched the base with sold. iron, It starts 45 or 49 Mhz randomly...

Next week I'll investigate...
The BOM for 45/49 MHz SC-Cut Driscoll oscillator does not include a trap to suppress the unwanted B-mode oscillation because all the crystals I did test (previous batch) started at the right C-mode frequency.
I have not tested the last batch, maybe they are a little different from the previous batch, and so they need the trap, like all other SC-cut crystals.
I'll test the only one I own from the last batch (all other have been already shipped).

[gabor80]

Thanks. I tested it at night, the heat of the soldering iron to the transistor base its jumping to the good 49 frequency, and the heat to the collector or emitter jumps to 53Mhz. (or I touch the C3 pins around). The other 45Mhz crystal just randomly jump, when I turn on-off. is the transistor good for here? The datasheet says its Hfe is just 100 around.

Is anyone who ordered the last group buy a 45 or 49 Mhz driscoll, trying the board?
Experienced anyone other this problem too?

(The AT cut clapp board is running perfect I try that too.)

[gabor80]

I tried the 11Mhz AT cut board connected to the Ian's Fifo. It updated a NZ2520SD crystal. Very good sound, very tranparent, detailed soundstage, precise highs, nice lows, much better than NZ crystal

[andrea_mori]

After some investigations...

the 45/49 MHz SC-cut crystals of the last batch seem to be different from these of the of the previous batch, so they start randomly at B-mode instead of C-mode (49 MHz instead of 45 MHz and 53 MHz instead of 49 MHz).

To avoid this issue the above crystal need a trap to suppress the unwanted B-mode and start at the right frequency, like all other SC-Cut crystals at different frequencies. The capacitor C3 in the schematic does the job.
BTW, in order to avoid overdriving the crystal because of the adding of the capacitor C3, a few components value have to be changed: C2, R1, R2.

Moreover the BFR182 seems to be too sensitive, so it was deleted from the BOM. I have tried several MMBT5179 and they work fine with SC-Cut crystals from 22 up to 49 MHz, so it can be used without any selection.

Follows the update BOM.

[andrea_mori]

Updated schematics, PCBs, BOMs and Assembly guide

Attached the assembly guides of all the boards available. They contain the schematic of each board, the BOM to source the parts and the instructions to build each circuit.

TWTMC-D assembly guide was updated about 45/49 MHz SC-cut crystals.

- TWTMC-C: Colpitts-Clapp oscillator revised
- TWTMC-D: Driscoll oscillator revised
- TWTMC-P: Pierce oscillator
- TWTMC-AIO: Dual Driscoll oscillator with power supply
- TWTMC-D&D: daughter board (power supply, dividers, and so on) revised to supply the Driscoll oscillator and the oven board
- TWTMC-OVN: oven board for SC-Cut crystals Driscoll oscillator
- TWTMC-DIL: DIL adapter for Ian's Fifo board

[gabor80]

Thanks Andrea! So I will buy the parts what needed for change.
Have you tried listening test since the last test in 2016? You have compared AT cut crystals with Pierce and Driscoll type board. Did you compare AT vs SC Cut crystals at same type board?

[Eldam]

Hello Andrea,

Does the new BOM apply to the first historical batch of AT crystals and PCB I have, or should have I to upgrade some pcbs ?

kind regards from France,

Eldam

[andrea_mori]

Originally Posted by gabor80

Thanks Andrea! So I will buy the parts what needed for change.
Have you tried listening test since the last test in 2016? You have compared AT cut crystals with Pierce and Driscoll type board. Did you compare AT vs SC Cut crystals at same type board?

No more listening test, too little free time.

I hope to know the impressions of the users.

[andrea_mori]

Originally Posted by Eldam

Hello Andrea,

Does the new BOM apply to the first historical batch of AT crystals and PCB I have, or should have I to upgrade some pcbs ?

kind regards from France,

Eldam

Hi Eldam,

if I remember right you got the TWTMC-C board, nothing was changed for this board.
In the meantime there are 2 more oscillator boards, the TWTMC-D Driscoll oscillator and the TWTMC-P Pierce oscillator.

Andrea