The size of electrolytic capacitors?

[elac310]

[QUOTE]Originally posted by stein2
[B] "I remain modest compared to your amount of filtering, and for starters remain modest on the amp as well. Just doing the finishing touches on mounting up the copper rails for the filters on a Pass F5 clone, start with a 500VA toroid with 2x18 + 2x18VAC (four 18V secondaries at 7.1 Amps each) then, 35A/500V bridges (one per each channel) and 2x25.000uF, 0.22R/25W, followed with 4x33.000uF. In total 364.000uF for two channels, not counting the smaller 470uF on the PCB and the block ones over the big electrolytes. Should be fine I think..."

Well, you say you end up with 364,000 uF for two channels, which is quite a lot. At these levels of capacitance, I don't think 360,000 or 600,000 uF make a difference. In fact, the last reason (I did not mention) why I chose the 4x150,000 caps is aesthetic. These 22cm (8 inches?) capacitors are the longest/highest I managed to find as they will fit well into, and fill up the future enclosure which will look rather empty otherwise :-))) ; nothing to do (I hope...) with Freud.

I very much like your idea of the 470uF decoupling caps mounted on the PCBs; this is also something I intend to experiment with, including with values available as film capacitors (MKP, MKT etc.).

[stein2]

Originally posted by elac310

Well, you say you end up with 364,000 uF for two channels, which is quite a lot. At these levels of capacitance, I don't think 360,000 or 600,000 uF make a difference. In fact, the last reason (I did not mention) why I chose the 4x150,000 caps is aesthetic. These 22cm (8 inches?) capacitors are the longest/highest I managed to find as they will fit well into, and fill up the future enclosure which will look rather empty otherwise :-))) ; nothing to do (I hope...) with Freud.

I very much like your idea of the 470uF decoupling caps mounted on the PCBs; this is also something I intend to experiment with, including with values available as film capacitors (MKP, MKT etc.). [/B]

I went for the maximal capacity I could fit into the future box because the F5 as mainly all the class A amplifiers are designed to work reliably and be as stable as possible with any load one attaches to the speaker out terminal...
My ESLs are nominally 4 Ohms, but like many of that sort, have a nasty tendency to drop below that nominal figure and the only precaution one can apply knowing the conditions during exploitation is to go a few Volts lower with PSU and increase the amount of current the amp can deliver when the impedance drops. That is of course, limited with many other factors, including the type and capability of the output device(s) to deliver the required "Umph, Kick and Bang" etc... I also opted for capacitors that go maybe halfway up the housing because once boxed and furthermore, when the components "settle in" after a few weeks I'll have to fine tune the amps again and filling the box all the way up would definitely not make my life easier when it comes to fiddling with the tiny screwdriver inside the 50C hot amp...

[lineup]

Originally posted by elac310

On a similar issue, I remember NP was also in favour of standard 25-35A rectifier bridges (in one of his papers available on passDIY.com I think he says he does not like too much fast rectifiers). But someone suggested that some of his post-Aleph designs do now make use of fast/ultrafast rectifiers.

Again, all this is probably another topic...

This is correct.
Nelson Pass has never in the past to my knowledge advocated explicitly
- Fast Recovery rectifier diodes/bridges
- Special Black Gate caps anywhere for his Diy Audio Amplifiers
www.passdiy.com articles projects
On the contrary!!!!
In his info and articles you find references to ordinary
- Silicon diodes rectifiers of good current rating.
- Standard good quality Electrolytic capacitors for filtering


Now, even Nelson Pass has to follow the road his users takes.
At least take in to consideration.
If people are obscessed with using fast recovery diodes,
at AC Supply frequencies of 100, 120 Hertz
than he did listen a bit .. and probably decided to go with the flow.
If his faithful users likes Dark, Black or any other color of Caps,
why tell them not to
And same with those diodes.

Nelson has never been too dogmatic, about details of less importance.
Fast Recovery will work as well as Silicon ordinary low price diodes.
Why bother .. let them have it
And be happy

[wakibaki]

Originally posted by lineup
.. and probably decided to go with the flow

Dead right, lineup.

You guys are arguing about how many angels can dance on the head of a pin.

Fine.

Have you tried listening to music?

w

Just follow good electronic practise as is considered adequate in other noise sensitive applications. e.g. radio.

[Nelson Pass]

Originally posted by lineup
Now, even Nelson Pass has to follow the road his users takes.
At least take in to consideration.
If people are obscessed with using fast recovery diodes,
at AC Supply frequencies of 100, 120 Hertz
than he did listen a bit .. and probably decided to go with the flow.
If his faithful users likes Dark, Black or any other color of Caps,
why tell them not to

Yes, a few years ago we switched our production over to fast rectifiers.
This was essential to meeting emi standards in some countries we export to,
aside from any sonic improvement.

As to capacitors, I recommend the Elna "silk" caps if you are using
electrolytics, otherwise we are using polyproplene where possible
and where caps are necessary.

But in general I don't like to take sides in the passive parts wars. There
are plenty of others with strong opinions.

[wakibaki]

Hi Nelson.

I'm sure neither lineup nor I intended to talk about you as though you weren't there.

w

[flg]

The size of Electrolytic Caps? Well, I'm going off thread but I don't think anyone will actually notice...
The Diode thing is not anything to do with ripple @50-60Hz. Any reasonable component spec'ed for the I and V will work in that regard. The only somewhat less than sublte aspect beside the heat dissapation would be what happens when you turn on the amp from a cold state. The inrush current from charging 2.2 Gigafarad of caps will be enough to weld most of your PSU into one solid peice of ??? Those Diode bridges N.P. suggests are relatively inexpensive and generally rated at 35A+, and momentarily much higher, capable of the inrush current of something close to his suggested cap bank.
But, this is DIY Most of us are out to make all the improvements we can afford, figure out, get by the wife, etc. The subtle part... When the diode bridge crosses 0V, it causes a little problem somewhat like a class B amp's crossover distortion. It has to somehow jump over two Vbe's without anyone noticing and it has trouble doing that. For that short time, only during 0 crossing, the standard diode will make a bunch of high freq noise You can see sizeable spikes on your scope if you look. I beleive those spikes are going back through the transformer and out the AC line causing the EMI problem N.P. just mentioned. Well, what do you think happens in your amp? That noise burst goes flying right through your 2mH inductor due to parasitic/leakage L and C and goes right into your amp rails A CRC may be better at attenuating this noise than a CLC. What about your PSU filtering? Well, I'm sure it helps a little but you have ESR and ESL in your filter caps and possibly even more of a problem with 2.2 GigaFarads worth. Your power Supply works damn good at 50-60Hz but I havent herd anyone say anything about that high freq diode noise???
Basically all these fast, soft, Silicon Carbide, schotky etc. produce less 0 crossing noise Using TV Damper Diodes (tubes) is said to be the best but I shouldn't go there...
I suppose after all that, I could move on with MHO to the topic at hand Maybe next post...