NAC 42 to Snaps connection

No, you don't. The 42 has only a 4 pin connection. The 42.5 has both a 4 pin and 5 pin. You need a 4 to 4 Snaic. If it's a 42.5 you very likely need a link plug for the 5 pin socket. 

It's a 42 normally used with a 110.

So you just need another 4 to 4 Snaic. 

Output to amplifier has 4 pin. Output to power supply has 5 pin. I just don't understand.

This is what the back should look like if it's a 42.5. Connect to the 4 pin socket. Put a link plug in the 5 pin socket. 

Don't forget that you connect the 42 to the snaps, and the snaps to the 110. There is no direct link between the 42 and the 110.  

Thank you I'm going to try (actually I'm going to tell the friend who owns it).

BTW then it shouldn't work connected via Snaic to the 110 without the 5 pin plug...

No, it won't work, unless of course it's been messed around internally over the years. 

HH, it might be worth posting pages 14 & 15 from the user manual for the OP, or he could look for himself......the clue is at the top of HH's screenshot 

To try to clarify - based on my own first hand knowledge....

An NAC42 only has a 4 pin DIN connection. Which connects to the Power Amp, or SNAPS via a 4 pin to 4 pin interconnect, which may be a SNAIC.

An NAC42-5 has both 4 pin and 5 pin connections. The 4 pin connects as above, while the 5 pin connects to a HiCap (or similar) via a 5 pin to 5 pin interconnect, which is always a SNAIC. 

When all else fails, re-read the instructions.....

Yes - the 4 pin connection allows a single 24v rail to be carried from the 110 to power the pre-amp. It also allows use with the Snaps which has a single 24v rail output. 

In this setup you either have 42 > Snaic 4 > 110 or 42 > Snaic 4 > Snaps > Snaic 4 > 110

The 5 pin connection (42.5 on) allows a Hi-Cap to be used which can provide 2x 24v rails to power the preamp

In this setup you have 42.5 > Snaic 5 > Hi-Cap > Snaic 4 > 110

If you have a 42.5 and it has a 5 pin socket then you need

42 > Snaic 4 > 110 or 42 > Snaic 4 > Snaps > Snaic 4 > 110 - in either case you will need the link plug in place in the 5 pin socket on the pre-amp. It's purpose is to link the internal 24v rails when a single rail power supply is used. 

Ok bit confused about that (sounds like a 42.5 as many have mentioned above) but if he uses it without the link plug and if that works ok with the 110 then just connect as so - 

42 > Snaic 4 > Snaps > Snaic 4 > 110

Ignore the 5 pin socket - sounds like it's been wired internally (so be careful and get it checked if you intended to add a Hi-Cap in future) which would need to use this connector. 

This is the way he tried first but it doesn't work. Also he connected the nac 5 pin output to a flatcap and the nac was powered.

I wonder if the Snaps may have some problems...

If it works with the 110 into the 4 pin socket, but now with the snaps into the same socket, there is an issue with the snaps. 

Regarding the preamp, it's a 42.5, otherwise it would not have the 5 pin socket. The .5 upgrade could be done by dealers, who wrote the '.5' on the back with a felt tip pen. Or, in the case of your friend's amp, didn't. I'd get the amps sent to Class A in Sheffield for a service and a check. I'd also think about getting a serviced chrome bumper Hicap, which is much better than the little snaps.