Upgrading the Tentlabs DAC (split from- Anyone use this clock upgrade?)

[Guido Tent]

Originally posted by Kenshin

Four legged XTAL (with internal oscillator) from a manufacturer making aerospace components should be something good.

Good for aerospace does not imply good enough for audio....... Again, a meaured spec of the jitter is welcome and could convince us of the quality. All other is useless. I include one meaurement of a TentLabs XO2 oscillator module.

[Joseph K]

Guido,

I know that it was not yesterday, the design phase. Having seen Your opinion changed since then, could You suggest something better for a tweaker type old customer of yours? Or, to put it in another way, do you consider it a possible tweak point, looking at it from a general balanced design point of view?

Thanks, George

[Guido Tent]

Originally posted by Joseph K
Guido,

I know that it was not yesterday, the design phase. Having seen Your opinion changed since then, could You suggest something better for a tweaker type old customer of yours? Or, to put it in another way, do you consider it a possible tweak point, looking at it from a general balanced design point of view?

Thanks, George

Yes, that deseign was finalised about 10 years ago

Nowadays I'd suggest a string of 3 red LEDs, biased by say a cr511. That gives a clean 5V reference. All you need is a buffer, for example an OPA134 with an emitter follower in unity feedback.

best

[Joseph K]

Thanks for the quick reply!

I would have some other questions / notes of this type. I was considering the idea of opening a thread at a certain point, maybe it could be useful for others as well. But now, pardon me, I just can't resist, in your opinion exchanging the TLC271 for some newcomers like
LMV 771 from nat.semi or opa725 or max4475 would go in the same direction?

Ciao, George

[Guido Tent]

Originally posted by Joseph K
Thanks for the quick reply!

I would have some other questions / notes of this type. I was considering the idea of opening a thread at a certain point, maybe it could be useful for others as well. But now, pardon me, I just can't resist, in your opinion exchanging the TLC271 for some newcomers like
LMV 771 from nat.semi or opa725 or max4475 would go in the same direction?

Ciao, George

Hi George

Yes, you could consider a thread on upgrding that DAC

Look for low input current noise opamps to upgrade the PLL

best

[Kenshin]

LED is a low noise component, but not high PSRR.

[bocka]

Look for low input current noise opamps to upgrade the PLL

And for low 1/f noise. And only CMOS or FET input. No bipolars. Input current causes a permanent phase error when connected to the phase detector output of the PLL.

[Guido Tent]

Originally posted by Kenshin
LED is a low noise component, but not high PSRR.

Ofcourse because I want it to stabilise

What do you think the CR511 is for ?

best

[Joseph K]

Guido,

Thanks again!
That power supply suggestion is sensible. It was not me who asked about the CR511...

Bocka,
Thanks for the goodwill. In fact, I was looking for these parameters.
The LMV771 seems to be readily available, RR opamp, input bias current is 0.2 pA [against .6 of the tlc], input offset current is 17fA [against 100 fA of the tlc]

What regards 1/f noise, this was what I was hunting for, the LMV771 has en=12.5nV at 100 Hz, against ~300nV of the tlc271.
in for LMV is 1fA, NA for tlc.
Wanted to put up here the noise curves, still fighting with it.

The other opamps perform equally or better. What I wanted to point out that there has happened a revolution lately in the cmos opamp field, and we could profit from it..

Ciao, George

[bocka]

On a first view the LMV751 is also promising