Hierarchy of Chrome Bumper Pre-Amps?

First question?  Best for what?

If best for a pair of turntables, tape decks, need for mono etc.. then only consider a NAC32 or NAC32.5. The latter is the later and better unit, with the ability to be powered from a dual-rail supply such as a Hicap.  The earliest bolt-down NAC32 is essentially a NAC12 with expanded input and mono capability.

If best for sound quality then it's not quite so straightforward.  JV always considered a NAC42 and NAC32 to perform essentially the same, just that one provides more facilities and inputs.  However, the NAC32.5 could be further upgraded with NA729 time-aligned boards and arguably this is best of the bunch.  However, out of my collection of CB shoe-box pre-amps, worst is probably a well used example of a NAC32.5, but there's also another slightly later NAC32.5 that's one of the best, along with a NAC62 that's also very good.  Most special of all is a particularly fine example of a NAC42.5 - one of about four that I have had and by far the best.  So, you start to see the problem; consistency back then wasn't quite as good as nowadays, and age and use have both ensured that all bets are off if trying to devise a strict hierarchy.  

p.s. Oh, and that's just judged via the line inputs.  The various phono cards present a whole new set of variables...

Basically, your best bet is to look for a good 32.5 and fit NA729 boards.

Thanks Richard, my usage would be line level, no phono (as I own no vinyl). Currently running the Bolt-down CB250 fronted by my UnitiQute and sounding goooood :-)

After the 32.5 came the 72 and then the 82 and then the 52 in terms of improving sound quality.

Again, as Richard has said, age/condition are important, but a "good" 52 will outperform a "good" 72 etc

Skyhigh posted:

Thanks Richard, my usage would be line level, no phono (as I own no vinyl). Currently running the Bolt-down CB250 fronted by my UnitiQute and sounding goooood :-)

In which case you need to fit the "Blank" boards or the "CD" boards or use the "Tape" or "Tuner" inputs

...except I have a lovely late NAC32.5 with NA729 boards - it sounds great but that NAC42.5 is extra-special, an aberration perhaps?

If it were me, and I didn't need the extra facilities offered by a NAC32.5, then I'd be looking for a really nice CB NAC62.  All the ones I've tried have sounded great, never come across a duffer (but that's not to say they aren't out there), even after all these years.  You should land a lovely one for around £200.

Out of interest Richard, how did the 12 compare to the later preamps ?

NA729 boards? Without looking inside my late (green LED) 32.5, how would I know? And where do they go? 

For me the 32.5 was an upgrade from a 42 (big knobs, red LED). The difference was huge! Immediate. No going back. A real revelation in clarity and timing and body. Still going strong, although a service from Class A a few years ago cleaned the 'stereo wall' (N.Peart).

James, my NAC12 is a very early one that has had a number of Naim upgrades over the years (for example it now sports ALPS Blue Pots) but hasn't had a service for some time, so maybe not entirely representative.  However, compared to the others it's very direct, if not as sweet or expansive.  Differences though are not massive - you can tell they are all essentially very similar.  It's just some have that little extra "je ne sais quoi" that is nigh on impossible to pin down but is the difference between excellence and magic.

Loki,

the NA729s (NA329) were an upgrade for the NAC32.5 - the upgrade replaced input NA324 boards with NA329s and NA321s with newer design NA321s to match the NA329s.

You would be able to tell by carefully opening up the pre-amp and looking at the numbers on the daughter boards.

This was essentially the main upgrade with the arrival of the NAC72.  However, an upgraded NAC32.5 with NA329 or 729 boards is not identical with a NAC72 - if you listen to vinyl, in some ways it's better because you retain the very useful Mono switch of the NAC32.5.

Richard Dane posted:

James, my NAC12 is a very early one that has had a number of Naim upgrades over the years (for example it now sports ALPS Blue Pots) but hasn't had a service for some time, so maybe not entirely representative.  However, compared to the others it's very direct, if not as sweet or expansive.  Differences though are not massive - you can tell they are all essentially very similar.  It's just some have that little extra "je ne sais quoi" that is nigh on impossible to pin down but is the difference between excellence and magic.

Thanks for the info Richard. Your warmed over 12 sounds (no pun intended) rather lovely. There's just something about the very early gear, maybe the simplicity with no superfluous functions, that is rather attractive. 

'Very useful mono button'

THank you Richard, I shall check later. What exactly is the advantage of the mono button? I do predominantly listen to vinyl, but have oft wondered. On my mc2 power amp for the PA system, we use mono bridge mode to double the power, but the switch is on the power amp not the control section (mixing desk). I guess that's not the same?!

The advantage of the mono button is that it cuts down on a lot of the noise that a stereo cartridge relays when tracking a mono cut LP.

So no power advantage then?!

If a stereo LP is cut properly in mono compatible stereo there is every advantage from the purely musical perspective to using the mono button as well. 

If the music depends on stereo effect, then the music is probably just candy-flosse ... not worth replaying twice. 

ATB from George

Loki, no power advantage. I think you are confusing this with a stereo power amp that can be bridged and used as a monobloc. Nothing to do with the mono switch on a preamp.

Thought so, just wanted to be clear. No end of rumours in Valhalla!