Power supply Capacitors

[Vivek]

I have an amp with 4700uF caps in the power supply.I want to know if increasing the capacitance(say to 10000uf)will help improve the sound.Thanks.

[datanasov]

It dependns of the power of your amp. Up to 25W it wouldn't improve the sound. I prefere to use 4x4700uF.

[Vivek]

My amp has a power rating of 21W RMS per channel and 250W PMPO.It is not high end stuff,but is reasonably good sounding.It does not matter because I plan to build the 60W amp from ESP.Thanks anyway.

[vdi_nenna]

I think it will help. I think it will tighten up the bass. When the amp needs more current, usually in the bass freq., it will have it on reserve.
There are formulas out there to estimate what you might need, but I think the more the better. But, on start-up, those Caps will put a strain on your bridge.

[Vivek]

Sounds good.I will give it a try.I can perhaps use a bridge of higher current rating if the present one fails.Thanks guys.

[mullins]

I saw your post and thought I'd give it a try myself. I had some 37,000 ufd caps for a future project so for kicks I swapped them with some 11,000 ufd in a Soundcraftsman amp I have. WOW there is a pretty big difference in the bass, with much cleaner bass at low levels and quite a bit more power before the onset of clipping. Now I just have to figure out how to FIT these in the case!

[Vivek]

I too can hear the difference in the bass.But Mullins,watch out for the bridge as has been pointed out by vdi_nenna.So let's kick *** guys.

[Eric]

OK, so if the caps are too big, the bridge can fail. Is there any way to determine the failure point BEFORE the failure actually occurs? Calculations, etc? Or, for a given size of caps, how can you determine the capacity of the bridge to support them - preferrably before they fail?

[vdi_nenna]

It does make a difference, doesn't it??

The caps will not drawl much more voltage (there may be a peak voltage...I'm not 100%, most likely!), but they will need larger amounts of energy to fill to capacity. This is a problem at start up. Ever hear the thump in your speakers when you power up some amps? That's where the problem starts, then it goes back to normal. All that energy gets drawn to fill up those large resevoir caps. (This is the argument for leaving you amp on all the time. But some think that leaving it on will degrade parts just as well, so which is it? I don't know. That's why it's an argument!!) The break down of the rectifiers happens over time. The bridge should be at lease twice the secondary voltage coming out of the transformer, and maybe 5 times the current drawl.

I keep refering to Nelson Pass and Pass Labs. They have a great article on his "ARTICLES" web page about power supplies. It explains power supplies pretty well. Also, read the A75 article from cover to cover. I learned so much from it.

Oh, one last thing!! Be real careful when working with Power supply CAPS!! I've seen them melt tips of screw drivers!! They can store a voltage long after the power is cut from them!!! It's their job! Find out how dissipate the stored voltage. Anyone know a good value and wattage of resistor to do it??

Great to hear the upgrade helped!!

[mullins]

Well I normally leave the thing on. As a matter of fact I have been running this particular amplifier constantly for about the past 3 years. Nothing has ever failed in it. So I am not worried about the rectifier failing. As for discharging big capacitors it is really quite simple, just take a screwdriver, grab the rubber handle and use the metal part to short out the capacitor! It is dangerous I am sure, but so is sky-diving.