KWAK CLOCK parts questions

[Tieftoener]

Elso and others...

I'm putting together a parts/order list given the list of items in the zip file.

I'm having great difficulty finding the Spectrol pot. Newark carries them, but they are out of stock and require a minimum of 200pc order. I have noticed that this pot has a very sensitive travel -> 25 turns... Is there another pot that others have used or can suggest that will be an adequate replacement since I can't find the darn thing anywhere?!?!?

2) I've been thinking about getting PPS Film or Polyester caps from Panasonic instead of the ceramic type as suggested. From my limited knowledge, I thought the film (and film/foil) caps were better high frequency performers than ceramic... comments? Recommendations?

thanks in advance...

[Tieftoener]

ALSO,

what size ferrite beads? impedance/frequency rating? 110ohms @ 100MHz sufficient?

sorry if I'm being a pain... I just don't like to have to rebuild prototypes... uh... errr.. rat's nests

Thanks guys (and gals)

[Tieftoener]

Yet another question...

'neosid' inductor... I'm clueless on this. Is there any particular orientation of this inductor that is better or worse? Is plain ferrite core OK, or should I look for a toroidal type?

Thanks, yet again...

[peranders]

You could email Mr. Kwak himself.

[Elso Kwak]

Hi Tieftoner,
For me it's difficult to give advice were to get parts as you live in the USA and I am at the other end of the big pond Europe.
To give you an idea which parts I am using:
The ferrite beads can be obtained from www.farnell.com Part# 323-4861.
The 2.2mH Neosid inductors are from www.conrad.de part# 535796.
If I recall right these are 21 Ohm DC resistance and rated for 105mA. As my clock only draws about 7mA this appears no problem. I believe www.mouser.com and www.digikey.com
have suitable inductors from other sources.
The pot I got also from Conrad but Farnell also sells it. Any other 2k pot also will do, as the adjustment is not critical at all.
I experimented a lot with other bypass caps like polyester, polypropylene etc. To my ears the difference was not audible. A little bit of improvement can be gained by placing a Oscon, 47 µF directly at the FET supply i.e. the Drain.

[Tieftoener]

Elso,

Thanks very much for the input!

I know that components can be extremely critical sometimes (as seen in the post comparing your clock to the Guido Tent XO2 clock). And I didn't want to risk changing something that might alter performance (at least for the worse).

To clarify, the pot doesn't have to be a multiturn? What exactly does the pot adjust so I know what to look for on my scope...? It appears to set the input level to the non-inverting input to 0. Why not just tie this input to ground? Should I be looking for a voltage value as close to 0 as possible at this pin, or should the non-inverting input be biased to one side of the supply?

One last question... should I go with metal film resistors to for lower noise and greater temp stability? Or are carbon film adequate?

[Elso Kwak]

Originally posted by Tieftoener
Elso,

Thanks very much for the input!

I know that components can be extremely critical sometimes (as seen in the post comparing your clock to the Guido Tent XO2 clock). And I didn't want to risk changing something that might alter performance (at least for the worse).

To clarify, the pot doesn't have to be a multiturn? What exactly does the pot adjust so I know what to look for on my scope...? It appears to set the input level to the non-inverting input to 0. Why not just tie this input to ground? Should I be looking for a voltage value as close to 0 as possible at this pin, or should the non-inverting input be biased to one side of the supply?

One last question... should I go with metal film resistors to for lower noise and greater temp stability? Or are carbon film adequate?

Hi Tieftoener,
The pot adjusts the duty cycle of the clock.
When adjusted correctly you should have about +1.4 to +1.6V DC at the wiper. It does not need to be a multiturn. I just like these Spectrol pots and they have a small footprint. I you connect the 50 Ohm coax with the 50 Ohm resistor at the scope end, you should adjust for the best possible symmetrical squarewave at the scope.

I am using 1% metalfilm resitors throughout. Maybe it also works with carbonfilm resistors. I have seen these in HF circuits.

I an early version I used the LT1016 as the comparator. The AD8561 simply gave a better sound.