It would be nice to have polymers in higher voltages but I don't ever see it happening - the demand just isn't there. I use them a lot and they just about always make an excellent replacement for tantalums. Also standard electrolytics but you have to watch that the low ESR doesn't cause problems.
They are pretty much a solution in search of a problem for me. The one place they are suited for is in some of the older HP (and other) power supplies that use a SCR pre-regulator... those just hammer the bulk filtering downstream of them. One of the very, very few places that I see the large Compulytic screw terminal capacitors failing.
The well known orange drops capacitors CDE 715/716p have nothing in common with the cheap cbb capacitors from eBay.
I used to believe this until I swapped a Solen cap for a Wima DC link cap with the same voltage, uf and esr ratings and the bass response in the amp changed drastically. Put a Solen back in and the bass response returned.
This was on a zero feedback SE 300B amp. I even tested the inductance vs frequency looking for a reason and they measured the same. I still can't explain what's happening, and in the past when I have reported this people blew it off as nonsense. I still feel a need to report that because IMHO this idea that all caps sound the same just isn't the case from my personal experience.
A lot of start caps in the U.S.A. are bipolar Al electrolytic , not metal film. According to this article,anything over 20uF is Al - Wiki on start caps
All the ones I have seen were encapsulated in black plastic.
We are all listing to our power supply, some of us just don't like to admit it. 🙂
Could very well be those that can't hear the difference a cap can make in some circumstances.
typo -> for "listing", read "listening".
Of course that is almost certainly absolutely correct because a single ended amplifier is effectively "pulsing" current continuously, which is the same charge/recharge cycle as ripple, albeit with a different timing frequency.
Only a properly designed push-pull amplifier can eliminate this "rippling". That can be done because the first stage multiplication inverts the signal and a concertina second stage phase splitter operating point can be chosen to use the same current as the first stage. That means the current simply recirculates around those first two stages and is invariant to the power supply. The remaining stage(s), being push-pull do likewise. Just put in a bias servo to keep this enforced. You thus become invariant to power supply capacitor concerns because you are running at constant current.
kind regards
Marek
And I feel some amp designs are way more sensitive to things like this than others.
I think another way is to have all stages differential and sitting on CCSes (a push-pull stage sitting on a high impedance CCS being akin to a long tail pair). The amp I am currently building is of this sort: 2 stage, input stage LTP IT-coupled to push-pull stage. Both sit on solid-state CCS having very high Z.
Okay so out of curiosity I made the experiment. Capacitor on a metal grille to allow air flow around, hair dryer pointed at it and monitoring case temperature with an IR meter. At 20°C the larger section had a capacitance of 14.36uF. After heating to a case temperature of 70°C (the maximum operating temp stated on the cap), capacitance was down to 14.28°C. After cooling the capacitance returned to its room temp value, suggesting the variation wasn't a measuring artifact.
So that would be a polyprop, and with a pretty good temperature stability as required for mains operation. Despite suggestions as it being not worth the time, I am tempted to try it in my current design. Not enough capacitance for input cap but I have a use-case cut-out for them in my regulators.
The larger section at the output to compensate for regulator inductive-like behavior and the smaller section as the error amplifier feedback capacitor; the common lead being connected to B+.
Last edited:
Thanks for actually measuring.
A rare jewel in an era when many go by "opinion" only.
Incredible temperature stability; only 0.56% variation in the "ambient to max rating" range? Wow!
In an industrial, non Audiophile or "Audio grade" part?
Not presented with any overblown salesman verbiage?
Double wow!.👍🏻
A rare jewel in an era when many go by "opinion" only.
Incredible temperature stability; only 0.56% variation in the "ambient to max rating" range? Wow!
In an industrial, non Audiophile or "Audio grade" part?
Not presented with any overblown salesman verbiage?
Double wow!.👍🏻