BPA300 mono block finished and measured

Hi,
Sorry for that. I do not know how to delete this picture item. It was proud and put a picture from one working test setting. Today I made the second circuit. It does not work at all. DC setting cannot change and 1= -1.6mV (negative) 2=0.5mV 3=-1.6mV (negative)
Total different to the first one.
I am afraid that 2 (neg) or one the positive LM3886 fails/broken. I think try to desolder these all and put new one's.
With regards Frits
 
BPA300v2, Stereo

Hi,
This is my new BPA300v2 stereo amplifier :eek:
 

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P-A, the RIFA caps is capable of delivery very high current, I accidentially shorted one fully charged 47000uF with a screw driver, a very big spark occured and the steel screw driver had a big dent on the surface!

I love them! ;)

can you say it is safe to use 40V caps, in application, whose value is close to rectified dc voltage (in your case you have 35vdc)?

i think to use 40V 22000uF kendeil caps for rectification in my lm3886 project but i wonder whether should i be worried about this issue...

can you help me?
 
My car is rated 220km/h , does that mean I should drive it with 220Km/h all the time?NO!
.

220 kph gets a little hairy in most cars and is usually not much fun - even in cars you might think were designed for it. I've done it in three different Lotuses with completely different results. The Esprit S4S would just drift up to 135mph without you noticing it, when you were trying to keep it below 100. The Excel SE would just get there and feel fairly OK, but even Autoroute bends would feel much tighter turns than they were. The Esprit S3 could get there fairly easily but it wasn't a great experience. The front gets so light that you know you are taking a risk; most of the surefooted qualities of the car have disappeared by that point, though you are still 15 mph off its top speed. Seriously not fun. I would dread to think what it's like in less good cars. You would have to be mad, reckless or under 25.

That bit of fun aside, it has no bearing on capacitors. First of all they are mostly used outside their specs anyway because the charging pulses tend to way exceed their ripple current ratings if the amplifier is being pushed. Secondly, heat is the main killer of capacitors, and that comes in the form of moderate shortening of life rather than catastrophic failure. Low ESR capacitors will obviously heat up less and that tends to translate into longer life. Mounting your capacitors outside the casing, as in some old amps like the Crown DC300, is actually a great idea which is overlooked these days. You can find reservoir capacitors that are still working just fine (ish) 40 years later. (It might be a good idea to change them but you will definitely change the sound of what you have got.) Thirdly, the rating is based on the plating times and voltages of the electrodes. The idea is that there will be no reversal of the electro-chemistry at the rated voltage. In fact quite a bit of latitude will be built in to ensure that is the case. Of course this will be cut to the bone if you are buying cheap Chinese capacitors that may well have been relabelled with new optimistic ratings in a Shenzen market, but it won't be the case for anything you buy through a decent distributor. (And if you want cheap and good then just pick Samwha - and tell Dawn I sent you.) Fourthly, if you are pushing a power supply hard you won't be getting its no-signal voltage. Almost any transformer you are likely to use will have sagged by a couple of volts, at minimum! To see by how much, just have a look at the drops in power between 8 ohm and 4 ohm loads - and 2 ohms if that's OK to test. That will give you the exact output resistance, or load regulation (which is so much less useful). Fifthly, if you really have a concern for your capacitors then parallel them up (which does not necessarily mean going up in total value, though you could). This will give them a much easier life - especially if you don't go up in value - and, as the ever-useful Rod Elliot points out, can also be a lot cheaper. You could also be creative as you do this. One of the most fun things I have seen in the last few years was a power supply on an amplifier from a Pure stack system (Pure did some great things, incidentally) and it paralleled a 6m8 and a 2m2 pair of small dimensioned capacitors on each side of its power supply. This gave a hugely improved impedance curve over a single 10mF capacitor. A brilliant idea!

In summary, I would say that running 35V rails from 40V capacitors is a day in the sun. 38V would be fine too. In fact, I see zero reason not to run the full 40V. And a few volts more wouldn't hurt either, especially if you are spreading the load. Often, the next step up is 63V, and that just becomes absurd in terms of cost. Nor are you usually getting any greater performance, but you are paying for the fact that they can't produce as many items per hour because of the extra plating time and voltage. There are plenty of places to get caught up in what is "good", or even "good practice" but this isn't one of them.
 
But electrolytic caps are normally rated for working voltage, not absolute maximum, ie a 10V cap can run at 10V for its entire life. So for 35V rails 40V caps are fine, just so long as that 35V doesn't rise above 40V due to load variation or mains voltage variation, ie the worst case working voltage is what matters.



If in doubt measure the leakage current of a 40V and a 63V cap and see if there's a significant difference - if so the 40V one is "optimistically" rated.
 
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