Bob wrote:
If all you are doing is running a Thunderbolt, you don't need a supply that's more quiet than most batteries.
Most batteries are *very* quiet -- it takes heroic measures to get *any* actively regulated supply into that ballpark. Indeed, one might be tempted to run a Tbolt off of three batteries, each one charged by a low-noise, high-impedance current source that puts out about .05 CV more than the Tbolt draws. One could even turn the charging off for short periods of "minimal noise" operation, if the batteries were suitably sized. However, in either case I would be concerned that the drift of one or more of the battery voltages (poor absolute regulation) might introduce another source of XO drift -- but I have not tried it.
The idea is to stop spending money when you have reached the "good enough" point.
I quite agree with you on this point (maybe I'd say "when you are clearly past the point where other errors dominate the performance envelope"). However:
People get reasonable performance off of straight switcher outputs. Adding simple linear + filtering gets you well into the overkill region on this application.
I'm not sure we know for certain how quiet is "good enough" for a Tbolt, or where the "overkill region" is -- particularly when the residual noise contains impulse hash from a switching regulator. I presume most time nuts would consider a 5 dB improvement in phase noise worthwhile for the relatively low cost/effort of using a good linear supply, if that level of improvement can be attained. The only systematic study I've seen is what tvb has on his web site, and it does not include data from a switching supply with external post-regulation and/or post-filtering.
Best regards, Charles _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
