My favourite cartridge has a carbon fibre former, so nothing to magnetise. (sorry Jan, drifting this off topic).
On topic, I note there is phono 1 and phono 2. Are they two preamps or do you switch the cartridge input?
On topic, I note there is phono 1 and phono 2. Are they two preamps or do you switch the cartridge input?
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It's probably correct, 0.22 F is perfectly normal for a supercapacitor. In fact you can buy 600 F, 2.7 V units as well, banks of those are often used for regenerative breaking of electric vehicles.
0.22 F would require some patience, as the voltage across the capacitor would take minutes to settle.
Then you can advertise it as a special preamplifier that has a "burn in" system that activates every each time you start it for better audio quality 🙂
Probably the wrong choice, far more capacitance than is needed and _very_ poor dielectric absorption performance, causing continual drift in voltage for minutes/hours? They may even be microphonic given the charge storage density is very high so that only a small deformation necessarily has influence on a lot of charge. Given the technology is based on activated carbon particles the electrical noise may be another issue.
At 0 DC bias and 0 signal you can only get thermal noise of the ESR, so look up the ESR over the frequency range of interest and you know the noise. Of course these capacitors are working at a DC bias of about 10 mV rather than 0, so I can't be sure my line of reasoning still holds.
As far as i know they can keep memory dump voltage supply for very long periods of time so i'm no sure how poor they are.not dismissing the possible microphonics though
Apparently 4 years ago, I tried to estimate how bad the noise with a substantial DC bias could get: https://www.diyaudio.com/forums/parts/56015-tantalum-capacitors-signal-path-3.html#post4933526
What you should not use in the audio signal path are Oscon alu polymers.
I discovered them to be very noisy with my low noise MC head amp.
Syn08 had his doubts but also tried and put it in one graph to compare both.
Richard Lee's Ultra low Noise MC Head Amp
What else can be said, prove is overwhelming.
Hans
I discovered them to be very noisy with my low noise MC head amp.
Syn08 had his doubts but also tried and put it in one graph to compare both.
Richard Lee's Ultra low Noise MC Head Amp
What else can be said, prove is overwhelming.
Hans
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That's very interesting! So some aluminium-polymer capacitors have a large and time-variant leakage that causes the excess low-frequency noise in the thread you linked to. It might be less of an issue for Jan with his DC bias of only about 10 mV, but you can better be safe than sorry and use normal aluminium electrolytics.
I opened the preamp up just today and discovered that those electrolytics at the phono headamp input are actual tantalums!
Jan
Jan