It might cause some parasitics. It might cause physical damage. Or it might have no effect. It's a fashion tweak.I have a practical question about the Fosi V3 amplifier - is it technically correct to solder a wima mkp10 0.15uF in parallel with 63v/2200uF capacitors? Doesn't this increase distortion in class D amplifiers?
I've already done this and there was no damage, but subjectively I liked the sound with Wima more - now I've returned to the factory version without them and the magic is gone!)It might cause some parasitics. It might cause physical damage. Or it might have no effect. It's a fashion tweak.
Almost certainly placebo/sighted bias.I've already done this and there was no damage, but subjectively I liked the sound with Wima more - now I've returned to the factory version without them and the magic is gone!)
Wima's of that value aren't as good for decoupling a power supply rail than some lower value ceramic caps around 10nF or compound using 1-10uF in parallel to it near the power pins of opamps or so which can be confirmed by RF measurements in the MHz to GHz range on the power-pins. It is pointless to decouple reservoir caps themselves because of the inductance of the traces going to the circuits.I've already done this and there was no damage, but subjectively I liked the sound with Wima more - now I've returned to the factory version without them and the magic is gone!)
They do something, because when comparing the sound with other class AB amplifiers, the "puff" when instantly switching with the selector button (between two amplifiers for one pair of speaker systems) is heard more clearly than in the version without Wima and at the same time Fosi goes into protection and switches off a little earlier than in the basic version.Wima's of that value aren't as good for decoupling a power supply rail than some lower value ceramic caps around 10nF or compound using 1-10uF in parallel to it near the power pins of opamps or so which can be confirmed by RF measurements in the MHz to GHz range on the power-pins. It is pointless to decouple reservoir caps themselves because of the inductance of the traces going to the circuits.
That said, most likely the wima does absolutely nothing for technical performance nor will the measurements improve but knowing they are in there WILL do something (positive) in your brain and if that's your magic...by all means solder them in and once again enjoy the magic. I am all for that but won't do anything for me... That's how perceptual bias works. Enjoy it and or playing with more expensive caps others claim bring even more magic. As long as you believe it will work for you.
If you do this without basic controls, what you have there is a brain trick having nothing to do with the actual sound.They do something, because when comparing the sound with other class AB amplifiers, the "puff" when instantly switching with the selector button (between two amplifiers for one pair of speaker systems) is heard more clearly than in the version without Wima and at the same time Fosi goes into protection and switches off a little earlier than in the basic version.
of course, that's why I asked the question, which I'll repeat again - does this theoretically improve or worsen the sound in class D amplifiers?If you do this without basic controls, what you have there is a brain trick having nothing to do with the actual sound.
It doesn't do anything consistent to the Class. The answer will be specific to the amplifier you are making the mod to (regardless of class). And no-one can answer it unless they measure the results, or do the detailed design calculations.of course, that's why I asked the question, which I'll repeat again - does this theoretically improve or worsen the sound in class D amplifiers?
of course, that's why I asked the question, which I'll repeat again - does this theoretically improve or worsen the sound in class D amplifiers?
That's right, but we all know that Fosi doesn't have the best schematic solution for the TPA 3255 - there are already better measured amplifiers and most likely even better ones are in the pipeline. There is no need to convince me of the usefulness of bypassing electrolytic capacitors, in Sansui and Accuphase amplifiers (and not only) this has been used for a long time, and in top models it is even multi-stage. I am interested in using this trick specifically in class D due to the specifics of their operation, which differs from traditional amplification classes.The question is too generalized. Most likely it won't do diddly-squat. There's a small risk of it forming an unintentional resonance circuit, but you'd need to do measurements to verify whether or not it happens in this specific case. It also helps to make a schematic before you just start soldering in more components. If Fosi already bypass the electrolytics with SMD ceramics, then the Wimas absolutely won't do any good.
EDIT: @antcollinet beat me to it
And what we are pointing out, is there is nothing in those specifics of Class D, that means "this trick"* applies more or less to class D than it does to any other class.I am interested in using this trick specifically in class D due to the specifics of their operation, which differs from traditional amplification classes.
I am interested in using this trick specifically in class D due to the specifics of their operation, which differs from traditional amplification classes.
As others have explained, this is not FOSI specific, or Class D specific. Using a bypass capacitor on the main electrolytic supply bank is probably not beneficial, because you need to know the layout and length of the rails which come after. You may make things unstable.That's right, but we all know that Fosi doesn't have the best schematic solution for the TPA 3255 - there are already better measured amplifiers and most likely even better ones are in the pipeline. There is no need to convince me of the usefulness of bypassing electrolytic capacitors, in Sansui and Accuphase amplifiers (and not only) this has been used for a long time, and in top models it is even multi-stage. I am interested in using this trick specifically in class D due to the specifics of their operation, which differs from traditional amplification classes.
No, he's talking about the bulk PSU capacitors. 63v/2200uF Electrolytics.I assume you're talking about improving the output filter?
But does it actually do anything there or it it for show? Where I've encountered it, it was the latter.There is no need to convince me of the usefulness of bypassing electrolytic capacitors, in Sansui and Accuphase amplifiers (and not only) this has been used for a long time, and in top models it is even multi-stage.
No, he's talking about the bulk PSU capacitors. 63v/2200uF Electrolytics.
In class A, AB, G and H there is no fast switching involved and usually one can get by with smoothing caps and the occasional decoupling near the power and/or voltage amplification stage to prevent instability.That's right, but we all know that Fosi doesn't have the best schematic solution for the TPA 3255 - there are already better measured amplifiers and most likely even better ones are in the pipeline. There is no need to convince me of the usefulness of bypassing electrolytic capacitors, in Sansui and Accuphase amplifiers (and not only) this has been used for a long time, and in top models it is even multi-stage. I am interested in using this trick specifically in class D due to the specifics of their operation, which differs from traditional amplification classes.