Options for NAC 12-help needed from old time Naim users

Posted by: Jens on 06 May 2002

Hi Folks,

My brother in law scored himself a bit of bargain last night: a NAC12S, NAP250 and homemade power supply for ca UK500, here in Perth, WA. Sounds very impressive, and that preamp is a cute looking box (narrower than a Hicap!). A couple of questions for old time Naim users:
a) What power supply options does he have with the NAC12? Should he look for a Snaps and then dual rail it so that he can power preamp and a CD3.5 (planned future purchase)? Can he do the same with a Flatcap? (Hicap is out for budget reasons, and I don't think the NAC12 accepts a Hicap).
b) How are the phono circuits configured? I assume NAC12S infers that the preamp contains S style MC boards or circuitry? Is this correct? Can he replace this with straight through boards if he wants to plug something else into the RCAs? Alternatively, are there MM boards available for the NAC12 if he decides to revive his old Dual turntable?

Looking forward to your input.

Cheers, Jens
Posted on: 06 May 2002 by Manu
NAC12S can only be powered by single rail PSU. A SNAPS can do the job perfectly.
Naim use to modified 12S for their own use with dual rail PSU, ask them, maybe they still do it.
In any case you can not use a PSU to power 2 dual rail devices (except the Flatcap2). The SNAPS was configured to power 2 single rail devices, but the 3.5 needs dual rail. You will need an other dual rail PSU for a 3.5.
You can use any 322, 323 board as phono board in the 12, and also the straight through board 326 (IIRC).

The 12S can sound quite well if in good order (recapped and cleaned)

Is your 250 a bolted case?

Emmanuel
Posted on: 06 May 2002 by Jens
Hi Manu,

Thanks for your quick reply. Let me see if I got this right: if my brother in law wants to use a single PS for both CD3.5 and NAC12, he needs to buy a Flatcap2, and convert the NAC12 into dual rail mode. Is that correct? Alternatively he can buy a Snaps to power the NAC12 only, and then whatever he wants to power the CD3.5 (which he hasn't got yet). That would have to remain a long term option, I suspect.

Good to know that he has a number of options with the phono boards.

The 250 is indeed the old bolt together case. Put together the pre and power amp are a nice bit of old history, but they still produce the goods, even after 20 years.

Cheers, Jens
Posted on: 07 May 2002 by David C
Jens,
Naim servied by triple digit serial number 250 last year. New caps transistors, the works, it cost about £150 and was a bargain for the improvement it brought. I don't think that the unit had been serviced since it left Salisbury.
Regards
David
Posted on: 07 May 2002 by Paul B
I owned a 12S years ago which I powered with an early Hicap. Unless the newer Hicaps are different today, a Hicap will power a 12S (at least it worked - very well - for me).

Paul
Posted on: 07 May 2002 by Paul Ranson
There was a sizeable gap (a year or two) between the HICAP and the -5 modification/revision to the 42/32. IIRC everybody upgraded to HICAP anyway. I don't know when the NAXO revision that benefited from two supplies was made.

Anyway a HICAP will work fine with a NAC12, but perhaps isn't an economic route.

Paul
Posted on: 07 May 2002 by Manu
Today a kit enter my shop for service (recap):
250 bolted,
12s,
naps : funny little box with a small laminated transformer, a bridge, a cap and a 7824.
Will post a picture of this first naim PSU, i think all components are originals.
I will check the 12 to see if it is easy to dual-rail it.

Emmanuel
Posted on: 07 May 2002 by Manu
As promised, some picture of NAPS. This one is probably original.
It has no serial number. On the sticker, instead of serial number, it is written: "110v".

Emmanuel
Posted on: 07 May 2002 by Manu
I'm not able to add multiple picture, so this is the second picture.

Emmanuel
Posted on: 07 May 2002 by Manu
And inside the matchbox.

Emmanuel
Posted on: 08 May 2002 by trevor chin
quote:
Originally posted by Manu:
Today a kit enter my shop for service (recap):
250 bolted,
12s,
naps : funny little box with a small laminated transformer, a bridge, a cap and a 7824.
Will post a picture of this first naim PSU, i think all components are originals.
I will check the 12 to see if it is easy to dual-rail it.

Emmanuel

hi manu,
I think what you have is a power supply for a early linn movig coil phono stage, called a pnag??? made by naim for linn. A precurser to the linnk??

Trevor
Posted on: 08 May 2002 by Jens
Manu,

That was good timing. Have you looked inside the NAC12S yet? What would be the benefits of converting it to dual rail? Is a flatcap 2 going to do a better job of powering it than a Snaps?

Cheers, Jens
Posted on: 09 May 2002 by Manu
Trevor,
It is realy a NAPS. Maybe used for what you said also.
It has been made to accomodate 250 users, to power their preamp.

Jens,
It will be for today. Post results in the evening, so tomorrow for you.

Emmanuel
Posted on: 10 May 2002 by Hon
I once owned a used bolt together cased 32 pre which comes with the same NAPS. The 32/Naps was bought together with a bolt together cased 250 power amp which I still use daily. The year of manufacture of the Naps is about 1977 which is printed on the reservoir caps. More details can be found on my webpage.

Hon
Posted on: 10 May 2002 by Manu
It is quite easy to dual rail a 12.
The power track is splited in 2 at the post.
Just cut the track on one side, insert a new post, solder it to the track under and to the 2nd power wire.
One supply will power the phono boards, the input boards, the led.
The other will power the output boards and the relay.

Emmanuel
Posted on: 12 May 2002 by Jens
Manu,

I'm glad to hear that it is a simple matter to dual rail the NAC12S. How does this improve the preamp? I can see that it gives my brother in law more options to choose from among power supplies, but is it also likely to be an improvement over the original Snaps?

Cheers, Jens