Recapping NAC32

[mcai7et2]

I have a rather old NAC32 (older than I am!) and I am putting together an order as RS at the moment for new PSU caps and schottky diodes for my CDP (Elna Stargets) and thought I would replace the Electrolytics in my NAC.

The obvious choice for the replacements is Oscons but they are not available in the same values as the current caps (47u @ 40v), is there a different value that would do as well (or better) or are there any other good choices for these caps?

Kind regards,

Edward

PS.

I am also planning to remove the relay board from the NAC, are there any caveats or things I need to consider before I do this. The pre is powered straight from my NCC200 power amp so there is no way I can change the order the components are switcheed on.

 

[chiily]

Edward,

On the MC boards there are two 47uF caps. The one on the power supply rail can be replaced with a 25v 56uF Oscon SP with a cleaning up of the sound with a touch of added pace. The other 47uF I've left as the standard ROE one.

I've had great results replacing the 22nF and 6.8nF polyester caps with polystyrene ones on the same value. Finding a 68nf polystyrene has proved very difficult, so look for a PPS (Polyphenylene sulphide) at 68nF. The result is a clean, dry(ish) sound, but fast.

If you want to go a little further then the input and output tants are well worth replacing on the MC card. Try either the BC128 or the 10uF, Oscon, SP.

A little further takes you to replacing the 15R resistors in the transistor ladder with some close tolerance metal films. Try measuring a batch and get the closest matching.

Moving to replacing resistors, have a look here

As for the rest of the boards: I've just replaced the power rail caps with the 56uF SPs.

The boards do benefit from a sprinkling of quality components, but don't go too far and only change one thing at a time.

As you have a 32 you may wish to investigate cutting a power track and converting to a 32.5. I'm not sure you can do this as I have a 32.5, but it's worth looking at. If you do split the power rails you'll need a 5 pin din, 240 deg so when you build a DIYHiCap with a couple of Andy's excellent Super Regulators it's a simply matter of plugging it in.

 

[mcai7et2]

Wow, a lot to think about there, thanks for the info!

I only have a CDP (at the moment) so have pulled the two sets of Phono boards. Lots to think about for the other bits of the Pre, and I will get a Rega 3 soon, I promise.

How tolerant are 25v Oscons to higher voltages? I am keen to try out Les's trick of boosting voltage to 30v from the supply, but do not want to toast my new caps in the process.

Thanks again,

Ed

 

[chiily]

Originally posted by mcai7et2
How tolerant are 25v Oscons to higher voltages? I am keen to try out Les's trick of boosting voltage to 30v from the supply, but do not want to toast my new caps in the process.

Thanks again,

Ed

I have read never to over voltage OSCONs, they fail closed cct, that is they stop acting as a cap and act as a wire! Not a good move.