capacitor polarity in a phono stage project

The power supply you have there requires a transformer with a centre tap -- this means a secondary with 3 wires. If yours only has 2, you need to get another transformer as the one you have is wrong.

What you need is a 36VCT, or a 18-0-18V transformer (both mean the same thing).

It is possible that you have two windings on your transformer (4 secondary wires, 2 for each winding). If these are both 18V windings, you can connect these in series to get 36VCT. However you need to connect them the right way or you'll get 0V (but that won't hurt anything).

I also think you can pretty much ignore all of what that guy says about one power supply sounding better than the other. When he says he maybe doesn't trust his ears, it's not his ears but his brain that is fooled.

 

It's simple.

1) use your multimeter to determine which wires are pairs (you may not need to do this)

2) connect one wire from each pair together.

3) apply power to the transformer (careful!) and measure the voltage across the remaining pair of wires.

4) if you measure something > 30V -- congratulations you have wired the transformer up as 36V centre tapped. The joined wires are the centre tap.

5) if you measure < 18V then you have one pair around the wrong way. Undo the join and swap one wire for it's opposite pair. Repeat step (3) and you should have success.

Note: there are several risks:

A) electrocuting yourself on the mains
B) connecting the mains to the secondary and generating a very high voltage on the primary
C) shorting a winding

To prevent (C) measure the resistance between any pair of wires you join in step (2) or (5) and make sure that there is no connection between them before you join them.

 

You only need a single power supply. It provides power to both channels.

 

Without looking at the project details, I would say yes. It is a little unusual (although not unheard of) to have separate power supplies for each channel. In general it's cheaper to make one large power supply instead of two smaller ones.

 

I have to warn you, every time I read that page I cringe at something they say.

Take this for example:

Complete male bovine excrement.
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and add OFC speaker cables to the list of woo woo improvements

Dave

 

Different brands actually do make a difference in some circumstances, and different types of capacitor certainly do. Go with the same type of capacitor as recommended and purchase from a reputable source (mouser, digikey, RS (Radio Spares, NOT radio shack), etc).

Just don't make us read any more of that page than we have to, OK?

 

Not audible differences, but poor quality electrolytics failing or having the wrong capacitance/voltage.

The obvious thing is the premature failure of low ESR caps (or capacitors in a high ripple-current environment). But there are also images going around of large metal can capacitors being filled with... a much smaller capacitor and something to make them feel heavy.

The important thing is to get quality parts where substitutions of fakes is less likely.