advertisement


Naim Nac 12

yurivv said:
As for the op-amps, I’ve seen scans of an old mag that contained the very first test by reporter Paul Rasmussen. He tested a pre/power 12/160 combo. According to the article, the pre-amp had inbuilt op-amps and the manufacturer had already made a new version (i. e. "v.2") that was entirely different from the old one. So personally, I believe the rumor that the first version of NAC 12 had inbuilt op-amps.
Click to expand...

yurivv said:
P.R. also mentioned that by the time the review was published Naim had already made the second version of the pre-amp, which means there were only a few pre-amps of version 1 in existence. I wonder if any of these have survived.
Click to expand...

I suspect that the Op-Amp version of the NAC12 was a working proto-type and never made it as a production item. This is one of the problems with small cottage manufacturers as naim was back then.

In the company I work for, access to proto-type and "pre-production" builds is very restricted and never seen by the general public. Once a Proto-type has served its purpose it is generally destroyed. I suspect this is how most main stream HiFi manufacturers (including naim as it is now) would operate today.

LPSpinner.
 
LPSpinner said:
I suspect that the Op-Amp version of the NAC12 was a working proto-type and never made it as a production item.
Click to expand...

This might be the case although the pre-amp featured in the article had a standard case with all the labels on the back.

Another thing I find surprising is that the DIN sockets the first versions had are completely identical to those installed on modern (black and olive) devices. I saw those sockets in pictures featured in the reviews of 12/160 and NAP 120.

I also used to have a NAP 120 with a modern DIN socket:

DP3M0413 by yurivv69, on Flickr

DSC_9875 by yurivv69, on Flickr


The pictures clearly show that the device underwent some late modifications (service) and I thought the socket was retrofitted. But the pictures featured in the very first review show it has the same socket. And the same sockets can be seen in the pictures of 12/160. Weird.
 
yurivv said:
This might be the case although the pre-amp featured in the article had a standard case with all the labels on the back.

Another thing I find surprising is that the DIN sockets the first versions had are completely identical to those installed on modern (black and olive) devices. I saw those sockets in pictures featured in the reviews of 12/160 and NAP 120...

...The pictures clearly show that the device underwent some late modifications (service) and I thought the socket was retrofitted. But the pictures featured in the very first review show it has the same socket. And the same sockets can be seen in the pictures of 12/160. Weird.
Click to expand...

Yes, It looks like niam started out using the PREH locking collar DIN sockets but changed to the latching type only to return to the PREH DIN plugs about the time they moved from the Chrome bumper to the Olive series.

LPSpinner
 
Jeroen sent me a leaflet of the Nac12. Preh locking din sockets. My units with serial numbers 53x and 105x are both fitted with the latching type.

nac12s.jpg
 
I see that the earliest devices had some orange electrolytic capacitors which were later replaced by ROE maroons.

I have device number 515 which has black ITT capacitors on all six boards. I first thought it was some kind of late modification, but if you look at the boards through a magnifying glass you can see that these capacitors were installed by the manufacturer. I’ve never seen such capacitors in any Naim device other than this one. Does anyone have any information on this?

10 by yurivv69, on Flickr
 
Jeam said:
Hi svein,

What do you mean by leaflet? Sorry, from Holland.......😄

Regards,
Jeroen
Click to expand...

Hi Jeroen,
FireMoon explained this well, you sent me an email with a pdf of a printed sheet of paper with info on the Nac12 and Nap160, Nap120 and Nap250 from the 70s. I just wanted to give you the credit for being the source of this interesting information:)

Best regards
Svein
 
Jeam said:
Hi svein,

What do you mean by leaflet? Sorry, from Holland.......��

Regards,
Jeroen
Click to expand...
As FireMoon says it's a part of the sales documentation. Usually a single piece of paper, folded up, that tells you all about how wonderful the product is, where you can get it and usually some promotional stuff like a discount or free gift to people who show this leaflet at the shop.

Also colloquially known as a "flyer" or maybe "flier". As in "Is there anything in the post today?"
"No, not really. Electricity bill, and a couple of flyers from the pizza takeaway and that new Chinese restaurant."
 
Aha, just learned some more english.....��

I've justput some 322 into my old nac 12 and it sound wonderful with the well tempered!
 
It is quite inappropriate to make a sweeping statement like Dmitre has, and it would be good if he would explain his experience/reasoning.

In my case I had (still have) an original Nac12s, which came with a tiny external power supply that was rather tired. Having consulted Naim I took both items to the factory to be refurbished, and was informed about the option to go dual-rail, which would allow the Nac12s to run off a HiCap or even a Supercap. At the factory I listened to the dual-rail Nac12 Naim had been using for some years to quality-check Nac-52 pre-amps and SuperCap power supplies as these were built. I had my Nac12s rebuilt to the same specification. As others have observed, providing you don't want additional inputs beyond Phono, Tuner and FM, this is a brilliant little pre-amp.

In my experience a Nac12 which has been refurbished does most definitely benefit from the dual-rail modification verus the original PS or a Snaps, especially if you are going to run your amplification into 3-way or otherwise demanding speakers. The chief audible benefit is that that the bigger power supplies then deliver all the pre-amp's range and subtlety to the amp/speakers.

I currently have 3 Nac12 pre-amps, as well as a modified Nac72 and a Nac60. In the past I have had Nac42.5, Nac32/32.5 and Nac52 pre-amps. I have also had Nap-135, Nap-250, Nap-180 and Nap-160 power amps.

My overall judgement is very similar to the view expressed by Gaius. First, make sure your Nac12 is in the best possible shape. Second, consider the cost/benefits of dual-rail. Third, aim for a Nap-160 as the optimal power-amp partner for your pre-amp and PS.

Skyebridge
 
skyebridge said:
It is quite inappropriate to make a sweeping statement like Dmitre has, and it would be good if he would explain his experience/reasoning.

In my case I had (still have) an original Nac12s, which came with a tiny external power supply that was rather tired. Having consulted Naim I took both items to the factory to be refurbished, and was informed about the option to go dual-rail, which would allow the Nac12s to run off a HiCap or even a Supercap. At the factory I listened to the dual-rail Nac12 Naim had been using for some years to quality-check Nac-52 pre-amps and SuperCap power supplies as these were built. I had my Nac12s rebuilt to the same specification. As others have observed, providing you don't want additional inputs beyond Phono, Tuner and FM, this is a brilliant little pre-amp.

In my experience a Nac12 which has been refurbished does most definitely benefit from the dual-rail modification verus the original PS or a Snaps, especially if you are going to run your amplification into 3-way or otherwise demanding speakers. The chief audible benefit is that that the bigger power supplies then deliver all the pre-amp's range and subtlety to the amp/speakers.

I currently have 3 Nac12 pre-amps, as well as a modified Nac72 and a Nac60. In the past I have had Nac42.5, Nac32/32.5 and Nac52 pre-amps. I have also had Nap-135, Nap-250, Nap-180 and Nap-160 power amps.

My overall judgement is very similar to the view expressed by Gaius. First, make sure your Nac12 is in the best possible shape. Second, consider the cost/benefits of dual-rail. Third, aim for a Nap-160 as the optimal power-amp partner for your pre-amp and PS.

Skyebridge
Click to expand...

Good post and good to see you back on pfm. :)

I also understood the Factory used the 12 to QC the 52, that's quite something!

I have never heard a 12S with a Supercap, that might just be awesome!

Do let me know if you ever want to sell one of your 12s.

Cheers,

Mark
 
Looks like a Nac12 would be a reasonably easy candidate to diy/clone, with original examples getting rarer and more difficult to get hold of. Would be easy to scan the underside of the circuit boards, use a photo-editing program to create new 'master' files, and etch duplicate boards. I think they were all one-sided pcbs? Would be quite keen on giving this a go.
Does anybody know if there are any scans out there of the motherboard & plug-in boards?

Cheers,

- John
 
Hi Guys;
I have seen versions of the NAC12 for use with a SNAPS (2x24V split rail) and NAP250 as a factory supplied option. From what I can gather, this version was the last generation of the NAC12 that had the latest main board where the output-muting relay was moved to a separate plug in card. The track layout on this PCB would easily accommodate the splitting of the 24V track on the main board. I’m not sure how easy it would be to split the 24V tracks into two separate feeds on the earlier version main boards or how you would actually divide up the feed. I understand that the 4 main boards (2 input buffers and 2 output boards) got one supply and the 2 phono boards shared the other 24V supply with the output muting board. Simply splitting the 24V feed into Left and Right channel is not how naim did it and besides, to do that properly would require a third 24V feed for the output muting circuit.

Before you decide to modify your NAC12 to split rail operation you need to consider how you will ultimately use your NAC12. If you are only ever going to using it with a power-amp that has a 24V feed then you may be better off leaving it as a single rail. In Particular, the NAP160 (bolt together case version) has its own 24V winding on the mains transformer. This to me suggests an operating condition that is the most optimum as you keep all your earths at one location and the signal passes though one cable and only one set of plugs, the 24V feed also gets its own transformer winding rather than scavenge from one of the main amp rails.

I would think carefully and consider how you ultimately wish to use the NAC12 before undertaking any major modification. Unlike the 32.5, 72 and the 62 which could be used either way with a bridging plug and were fitted with both 4 and 5 pin sockets that allowed either single or split rail operation, a NAC12 is either single or split rail operation. You become locked into one configuration or the other unless you drill into the casework to fit a second socket (and make up a special bridging plug) or by making up you own special 5 pin to 4 pin interconnecting lead for the times you want to run from a single 24V feed and 4 pin power-amp socket. This latter option sounds the most elegant to me as you are not unnecessarily diverging from the original NAC12 appearance or configuration. If you do convert the NAC12 to split rail make sure you use a 240 degree 5 pin socket rather than a standard 180 degree 5 pin socket for the 2x24V pre-out socket and make sure you observe the standard naim pin configuration. The last thing you want to do is push 24V DC back into another source component then wonder why it wont work any more.

Look forward to seeing lots of pictures of the finished project. :D

LPSpinner.
 
There's a lot of good sense in the last post. The way you split the power rails should be guided by what you anticipate your use to be. In all the chrome bumper and olive NACs that are dual-railed Naim chose not to split the rails by channels. This leads to a situation in the 32.5 and 72 if you don't use phono boards or the tape out buffer boards you are effectively back to a single rail preamplifier.

I've made a DIY preamplifier which has a 12 motherboard in a 72 chassis. This arose because I bought a 72 with a butchered motherboard and a 12 motherboard that someone had stripped out of its original chassis. This project has been documented in the DIY section before. I've now split the rails so that one powers the left channel and logo display whilst the other powers the right channel and relay board (325). This is achieved with just a few track cuts and links and is easily reversed. Giving a third power rail to the relay board and logo is possible but I doubt if it would reap any substantial benefits.

My power source is a CB SNAPS fitted with an Avondale TPR4 and I currently use a NAP140 making a very nice little system.
 
LPSpinner said:
Hi Guys;
I have seen versions of the NAC12 for use with a SNAPS (2x24V split rail) and NAP250 as a factory supplied option. From what I can gather, this version was the last generation of the NAC12 that had the latest main board where the output-muting relay was moved to a separate plug in card. The track layout on this PCB would easily accommodate the splitting of the 24V track on the main board. I’m not sure how easy it would be to split the 24V tracks into two separate feeds on the earlier version main boards or how you would actually divide up the feed. I understand that the 4 main boards (2 input buffers and 2 output boards) got one supply and the 2 phono boards shared the other 24V supply with the output muting board. Simply splitting the 24V feed into Left and Right channel is not how naim did it and besides, to do that properly would require a third 24V feed for the output muting circuit.

Before you decide to modify your NAC12 to split rail operation you need to consider how you will ultimately use your NAC12. If you are only ever going to using it with a power-amp that has a 24V feed then you may be better off leaving it as a single rail. In Particular, the NAP160 (bolt together case version) has its own 24V winding on the mains transformer. This to me suggests an operating condition that is the most optimum as you keep all your earths at one location and the signal passes though one cable and only one set of plugs, the 24V feed also gets its own transformer winding rather than scavenge from one of the main amp rails.

I would think carefully and consider how you ultimately wish to use the NAC12 before undertaking any major modification. Unlike the 32.5, 72 and the 62 which could be used either way with a bridging plug and were fitted with both 4 and 5 pin sockets that allowed either single or split rail operation, a NAC12 is either single or split rail operation. You become locked into one configuration or the other unless you drill into the casework to fit a second socket (and make up a special bridging plug) or by making up you own special 5 pin to 4 pin interconnecting lead for the times you want to run from a single 24V feed and 4 pin power-amp socket. This latter option sounds the most elegant to me as you are not unnecessarily diverging from the original NAC12 appearance or configuration. If you do convert the NAC12 to split rail make sure you use a 240 degree 5 pin socket rather than a standard 180 degree 5 pin socket for the 2x24V pre-out socket and make sure you observe the standard naim pin configuration. The last thing you want to do is push 24V DC back into another source component then wonder why it wont work any more.

Look forward to seeing lots of pictures of the finished project. :D

LPSpinner.
Click to expand...

Mmm, shirley anyone contemplating turning a 12s into a 12s-5 would use it with a outboard PSU - a HiCap or, in my case, an emitter-follower PSU designed by a friend of mine (who designs amps for a living) outputting 2x +24v?

I didn't have any problem reconfiguring the power tracks to drive each channel independently (there aren't any phono boards in it) and it sounds very nice - although this is not in my "main system" and I'm not using a Naim power amp. (I don't think I have an output muting board?)

Sure I should probably extend this concept to drive each of the 4 PCBs independently but the cost/benefit ratio of this would be small, methinks.


Regards,

Andy
 
I’ve got almost nothing to add to LPSpinner’s post but I would like to share some of my personal experience. I’ve had four NAC 12 preamps, one v. 2 and three v. 3, two of them were serviced, one done by the factory and one by myself.

I’m not going to comment on dmitre’s post that splitting rails will ruin NAC 12’s sound since I’ve never had such modified versions. But I’ve had all sorts of vintage Naim components, almost all of them in fact, except the top line, so I’ve been able to try lots of possible combinations with my NAC 12s, including a Hi-Cap, but I got the best result from a v.2 preamp powered by a NAP 160.

I know dmitre personally, and he gave me his own set of 12/160 for a listening test. It produced a very similar result. The use of external power supplies enhances the formal characteristics of the sound but definitely makes a listening experience less engaging. I don't think a dual rail PS would substantially improve the situation as compared to the single rail mode.

I now have a NAC 82/Supercap as my main preamp, and although it demonstrates (on some records) impressive superiority in terms of formal characteristics, I often find it enjoyable to go back to my NAC 12. Perhaps that’s what dmitre meant when he warned against splitting rails and using advanced power supplies.

I haven’t tried the Avondale wiring scheme yet. I have a faulty NAP 110 I’m planning to rebuild and turn it into a sort of SNAPS with a modern regulator (Avondale TPR2?). Let's see how the NAC 12 will behave after that.
 
Hi Guys:
I have said this before in several threads, but the NAP160’s 24 Volt feed is unique amongst the niam Power-amps in that it is fed from a separate winding on the NAP160’s transformer. With a NAP160 you basically get a SNAPs built-in. Based on what I have seen this is the case for both the “bolt together” and the later “chrome bumper sleeved” version of the NAP160. The other naim amplifiers scavenge their 24V feed from the main positive rail of the amplifier. I'm referring to chrome bumper and olive only, I'm not sure about the current black case / green logo series of amplifiers. Like yurivv I quite like the sound from my NAC12 when powered from the NAP160, and that is generally how I use it. it just seems right.

When you look at the circuit for each board, (phono – MM & MC, input buffer and main gain board) they all have an amount of power supply decoupling fitted to each board. As an Engineer and some one who occasionally builds his own stuff as well as restores vintage gear, I often ask my self does the dual rail actually do anything? Is it the dual rail that creates the improvement or is there some other factor involved such as a modified earthing path or modified signal routing that results from the addition of the out-baord PSU, - Or perhaps we are all being fooled… :eek:

LPSPinner.
 
You must log in or register to reply here.


advertisement


Back
Top