build power supply for35vdc rails

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Hello and hi,

I am in the process of getting ready for another amp, solid state this time and I want to build a good power supply giving 35-0-35 vdc. A few questions please: are electro caps rated for 50 volts good enough or do I have to use 63 volt. I wanted to use the panasonic fc but digikey only go to 2200uf 50 v or 1800 63v. When you make that jump in voltage the price goes up. I thought of using multiple smaller electros in parallel rather than let's say 4 10000uf 50-63v; one transformer'400va{eventually] may use a 160va for now I have on hand. dual secondaries. 2- 35a bridge rectifiers. I source parts from the USA or Canada. In the big electro's how are the panasonic ts? or are there any others I could consider here in north Amer.?

thanks and happy holidays,
doggy:cubehead: :Present: :santa:
 
greetings all;still exploring cap choices

For something to do, I pulled the top off my lm3875 chip amp. I wasn't planning to keep it, so I stripped off all the extra ps caps I had put on earlier. using it, it didn't sound to bad with the original 1500uf pana. fc.; but a little harsh. So I was having some fun and removed the fc's and put in just 2- 100uf on each side. It works but not enough power. I found out I don't like the panasonic fc's-strange that; but stranger still is what I ended up using and liking. You know those 330 uf 200volt caps you find in most computer ps? the ones no one think they are any good for anything? thats what I put in and they sound excellent. I also tied the 2 caps together with a 200 volt 470 on each side. I also increased the gain by adding a carbon comp 285r to the bottom of the board. The chip seems to have woken up but also a little more diode noise which I have not been able to fully suppress. This is the briangt kit.

cheers
doggy:)
 
Guys...

The rule for "working voltage" in caps is to run them AT their working voltage. A slight increase, the 20% cited by Quasi, is fine but there is no motivation to go further unless you suspect that you may exceed the MAXIMUM or SURGE voltage.

Electrolytic's benefit by being run at or near their rated working voltage. This maintains the chemistry of the plates.
 
Off Topic

Poobah,

The dog trick works very well.
My dog went nuts to get the third biscuit out of my pocket.
(then she stopped--knew there wasn't a fourth one)
My wife is convinced it has nothing to do with counting -- the dog just sniffs the biscuit on me-- but I still think it's a good party trick.


Andy
 
Andy,

Well there would have been crumbs with all their freshly exposed surface area still in your "empty" pocket... and the dog wasn't interested in those.

Three IS a fairly large number... we're talkin' math here. Were it my wife, I would suspect jealousy...

;)
 
cap related questions

Is there a difference in electrolytics if the mfd is the same but the voltage rating is different. Yes using the cap within its voltage limitations. To my observation the higher voltage rated cap is bigger. What is the internal differences and should they sound the same?Would either one be better ?
Cheers
doggy :confused:
 
Yep,

Same capacitance... bigger voltage... bigger cap. Caps DON'T benefit (or your sound) by being run under their WVDC. Voltage, at the rated Working Voltage Direct Current is required to maintain the health and internal chenmistry over time... Also, caps with higher voltages often have worse "ESR" relative to their capacitance. ESR is generally bad in audio.

:D
 
A lot depends on the DC voltage surge the circuit may expect to see... regardless of "working voltage" the max or surge voltage shold NEVER be exceeded.

Also in the last decade especially, electrolytic technology has advanced to the point where is has become harder and harder to get small value/voltage caps. Many times you will see 200 Volts caps on the output of a circuit because these are the caps that they also bought for the input... a means of reducing inventory.

Read the manufacturers recommendations... very hard to get to... and you'll find what they say about operating voltage... keep in mind it is all BS... they say they will last 2000 hours... and they last 20 years... most of the time.
 
doggy said:
I wonder why 200 volt caps are found in most computer supplies?
Seems overkill for the output vdc.
cheers
doggy
The power supply is an offline switcher, it rectifies the AC mains directly, smooths it with the 200 volt caps, chops it up at a high frequency and can then use a smaller transformer. I suspect there would be some lower voltage caps as well.
 
Very good poobah, that's what I suspected with manufacturers; and also in my experience many caps years old are still good; although I have some cardboard wrapped caps from a baldwin tone cab that i would think twice about using.

I don't know about switching supplies-but I could probably find out; yes there are smaller caps; 16vdc.

I wonder if 2 supplies can be hooked up in series to give 24vdc, like batteries? or 3 to give 36vdc?

cheers
doggy:)
 
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