PA100 (x2 LM3886) FeedBack Capacitors

[Al1B]

as you can see there are two Capacitors (C2 & C4) in this Schematic, that better be non-polar version....

i put two 220uf 50v in series with negative pins connected to each other and got something around 110uf at last....

can somebody explain me the difference this 10uf can make?

and the other thing,, What is so special about "BlackGate STD" capacitors, i tried to search on google but no results...

thanx Already

[sweetperfume]

does this LM3886 require a stabilized power supply....i got two of them and just blew up when i tested those

[kimk]

Electrolyte capacitor connected in series capacitor nonpolar when after ...

10UF may be too small, is not conducive to the low-frequency extension ..

Large capacity equivalent series inductance and large leakage current, dissipation factor will be big ..

[AndrewT]

polar electrolytic are OK in those locations.
Add protective diode in at least one direction +ve of diode to +ve of electrolytic.

You can also add a protective diode in the opposite direction if the electrolytic voltage rating is at or less than the -ve rail to power ground voltage.

[AndrewT]

Originally Posted by sweetperfume

does this LM3886 require a stabilized power supply....i got two of them and just blew up when i tested those

no.

[Al1B]

Andrew T: so u say i use the ones i made with a little difference in capcitance ? or normal electryicals ? which makes better results ?

im yet wondering what makes those black caps (1000uf 50v) that big they are...

[sgrossklass]

Absolute values of C2 and C4 are not too critical, they're only needed to reduce gain to unity at DC and cutoff is plenty low enough for that. Real bipolar ones would be preferred, though with 1k of series R it's not too much of a deal either.

1000µ buffer caps seem a little excessive, they're less than an order of magnitude smaller than typical power supply bulk capacitance. Anyway, it doesn't hurt either.

[jcx]

C8,9 are a bad idea - don't put C there, you could disconnect them from the -in and gnd those ends of the caps

also from the pic I bet the PCB power layout is the classic wrong +,- PS on opposite edges of the board

[danielwritesbac]

Originally Posted by Al1B

as you can see there are two Capacitors (C2 & C4) in this Schematic, that better be non-polar version....
i put two 220uf 50v in series with negative pins connected to each other and got something around 110uf at last....

can somebody explain me the difference this 10uf can make?

and the other thing,, What is so special about "BlackGate STD" capacitors, i tried to search on google but no results...

thanx Already

A polar cap datasheet may also list its reverse voltage tolerances. For example, a 6.3v cap may have insufficient reverse tolerance. However, a 25v polar cap may have enough reverse tolerance for the job. Check the datasheets.

A larger NFB cap can "allow" louder lowest notes, so what is the percentage difference between 100 and 110 and how much many more notes lower might that be able to play? Two. It can pass about two notes lower pitch.

There are many interesting bass effects possible in the relationship between the input cap versus the NFB cap.

Why not un-series your 220uF and use the 220uF values for NFB cap for half the distortion? Hey, no problem going bigger as long as its clear (a good performing cap). Also potentially helpful to treble is to add a little 10nF inexpensive polyester in parallel to the NFB cap.

Most audiophile capacitors are also know as "Low Impedance" and "Low ESR" which are very useful types to put at predrive and "right next to the chip" as well as useful for signal caps. Many manufacturers make a selection of low impedance cap.

If building without a scope handy, C8, C9 are actually a good idea for Parallel Non-Inverting LM3886. The C8, C9 caps promote stability, and its better to promote stability in some way rather than do without.

[Marc Vi.]

To have a - 3dB cutoff frequency of 4 Hz, C2 and C4 should be 39 microFarad. The nearest by value is 47 microFarad. So you put in serie two capacitors of 100 microFarad, voltage reversed connected.