Aleph 2 Supply Filtering

[macka]

Hi guys,

I am currently building the Aleph 2 and are currently considering what to use for filter capacitors.

Can anyone advise if it is better to use multiple capacitors, say 10 - 15 x 10,000 +- rather than say 4 x 20,000 +-. for channel.

I assume that bigger hi voltage caps would have good ripple current rating, but on the other hand a number of smaller caps in parrellel may offer lower ESR at hi frequencies and similar ripple rating.

Is this correct?

If I use smaller but many what is the best way of wiring them up?

I ask this as I have found useful quantities on ebay.

Any comments for recommendations would be welcome.

regards

macka

 

[FEThead]

used caps

macka,

You are correct when you say that bigger HV caps generaly have better ripple current rating but a number of smaller caps may have lower ESR. You have to know more about the individual caps to make that call. And when you buy used stuff it can be hard to tell exactly what you are getting. And then they may have been sitting around for awhile, or have had a "rough" life and deteriorated.

I suggest you use seperate wires (as thick as convienent for minimum resistance) for each cap. ("Star" configuration as opposed to "long chain" if that makes sense.)

If you have a massive low ESR cap bank you will have a huge in rush current when you turn the amp on. Either add some circuitry to limit that inrush or be sure your transformer and diodes can handle it.

If you buy them on ebay and don't like them you can resell them on ebay! (been there / done that)

As for the high frequency stuff from the amp, use smaller caps (a few uF, good quality) mounted close to the amp.

Happy building and listening!

 

[GRollins]

Mind you, there's another way of going at this whole capacitance thing. Look at what it will cost you $/uF. Make a spreadsheet. Divide it out. You'll find some interesting things along the way.
If you choose to buy surplus/used, you're on your own in every sense of the phrase.

Grey

 

[HarryHaller]

Surplus caps

1.There are some excellent buys on surplus caps in the USA. I don't know about shipping to down under but for us in the USA the following link has a great selection.

2. The Sprague 36D series, the Mallory CGS, and the CDE computer grade caps are great for power amps.

3. I would go maybe 10 to 20V over the working DC voltage for your application. Too high a voltage leads to increasing ESR.

4. Do some research. Get a part number from the Suplus supplier and go to the Web for data sheet.

5. Form the caps with a large value resistor as in Walt Jung's article. You can weed out bad caps before you blow anything up.

6. Small high quality Bypass caps should go close to the circuit you are regulating to bypass the inductance of the large caps and thier wiring. A 220UF in parallel with a 2uF film works great. If you are going to fuse the supply, this is good place for the fuse, after the big supply caps and before the local bypass caps.

I found some of the best sounding large filter caps (RIFA) made in a surplus store for about a 6th of retail for new ones. I didn't know anything about them when I saw them first. I did a little research on the web and went back and purchased all of them. Pass on the Grey poupon....for advice that cuts the mustard.

H.H.

http://www.surplussales.com/ElectrolyticsList.html
http://www.capacitors.com/pickcap/pickcap.htm

 

[macka]

Supply Filtering

Hi Guys,

Thankyou for your very helpful input.

Well, I bit the bullet basically on the price quantity issue and have bought quantity of (70) 15,000 uf 63 volt Samhwa brand from a trader in the USA for US $40.00. The shipping cost almost as much as the product! But they sell for about US$10.00 each down here

They guy had a number of boxes so I assume they were NOS.

They appear unused and sealed in the box (internet image) so it will be intersting to see what happens when they arrive in about 4 weeks.

For the layout I thought a E shaped with a pair of = pads (=) representing -+ inbetween the two ends like the giagram below might work . (This took ages to draw!)

>

> (a la Aleph 30 image from Volksamp)
> ie i l================= (earth)
> l l - - -
> l l + + +
> l l =============== + positive
> l l + + +
> l l - - -
> l l=================== (earth)
> l l + + +
> l l - - -
> l l ================ - negative
> l l - - -
> l l + + +
> l l=================== (earth)
>
>
Note I would like to fit them into a compact square chassis like the original Alpeh's

regards

macka