Naim Pre Amps

[neiljadman]

Slightly off topic... but I'm curious! One reads of "chrome bumper", "olive" etc but I don't recall seeing a variety of different topologies etc... people say "ah what you need is the olive era one" etc/whatever... call me a cynic... but are they basically all the same apart from restyled casework? Are any differences just a few resistor value changes as you mention re specific pre amp models as above?

Same basic topology and new casework yes but as CAD design and Circuit Board manufacture technologies improved Naim moved from hand drawn single sided boards to CAD design, through hole and then full two layer boards. Whether that really resulted in any sonic improvement is anybody's guess.

 

[nobeone]

There is a theory the hand drawn, and hence mostly copper single sided boards that were chrome bumper era, sound better than the sight revised layouts CAD drawn (thinner tracks, they didn't copper fill to the same extent) olive era boards. Essentially the same circuits, components, but different PCB ...

 

[Jonathan]

Also in moving from the 72 to 102 to 82 there were some component values changed to the input buffer (TA or 729) circuits. Interestingly the values in the 72 were the same as the 82 but the 102 used different values (cynically some might say in a deliberate downgrade/compromise to create the upgrade path). IMHO the 102 certainly benefits from the values being changed back to the 72 spec -along with a few other mods of course!

most interesting - i remember demo-ing the 102 at a dealer and getting into a bit of an argument with the dealer over the fact that i thought my olive 62 sounded much better than the 102 - dealer contended it was quite impossible of course ... but this might explain why that was

 

[neiljadman]

most interesting - i remember demo-ing the 102 at a dealer and getting into a bit of an argument with the dealer over the fact that i thought my olive 62 sounded much better than the 102 - dealer contended it was quite impossible of course ... but this might explain why that was

Remember though that the 62 used 324 type input buffers as opposed to the 72 and 102s 729 style input buffers.

 

[colasblue]

62's always had CAD laid out boards. To get hand drawn boards you need the original 12's 42's and 32's (note not the 32.5's and 42.5's).

I don't think the boards make very much difference most of the time in the pre amps but the carbon composition resistors vs later metal films possibly do.

The only situation I've observed where board layout is important is in power amps in active systems.

Amps with different regulator or amp board layouts generally don't gel so well as ones with identical layouts.

The board is an active component in any real world circuit so different layouts will perform and measure slightly differently, but you can only really tell when there's an explicit real time comparison going on between channels, be that L/R or around the crossover regions in active systems.

I actually have a quad railed 42 which I occasionally drop into replace my 82 and they are way more similar than different.

The 82 digs out more detail which is probably the 729 circuit vs the 324 but the 42 boogies along very nicely in a way that the 82 doesn't quite match.

 

[sq225917]

I think you're wrong, the 72 defo had hand drawn, euler curve boards. Cad boards didn't come until much later.

 

[booja30]

If you look at the phono boards over time, the earlier ones look like psychedelic art, and the later ones have lines of uniform thickness and perfect arcs. All the boards in my 72 are like the latter.

72 boards:

Hand drawn early rev 323:

 

[Dowser]

To answer the OPs question, in the case of the 32 and 62, yes, they both used the same 321 and 324 circuits with identical component values. The 92 used the Nait3 preamp board which may have used simplified versions of either or both circuits - (I'll update this if I go through my NAIT 3 files). The 202 and 252 are the new casework versions of the Olive series 102 and 52, and would have used the 729 style TA input buffer in place of the 324 buffer; see discussion below.

There were some subtle component value changes to the 321 gain circuits between the 42/32/62 and 72 which are listed on the Acoustica site.

Also in moving from the 72 to 102 to 82 there were some component values changed to the input buffer (TA or 729) circuits. Interestingly the values in the 72 were the same as the 82 but the 102 used different values (cynically some might say in a deliberate downgrade/compromise to create the upgrade path). IMHO the 102 certainly benefits from the values being changed back to the 72 spec -along with a few other mods of course!

The main difference between the 102, 82 and 52 is actually in the number or power rails that can be used - see my posting for 102 mods for more details: https://drive.google.com/file/d/0ByAeclGjRjLUQjZEa0d4U3hhVGM/view?usp=sharing

But right through to the 52, the components used were the very same except for those Samwha electrolytics replacing the ROEs, which I think happened with the 102, though this might only have been on later years.

Now I have never pulled apart a 555, but I have heard that the tantalum signal coupling caps made way for Wima MKS2 film caps, can anyone confirm that? And I do know that one of the resistors in a critical position in the 555 preamp was tightly measured, sorted and matched to a specific value - I have an ex NANA tech's set of bench repair components and one of the drawers is labelled to that effect.

Excellent reference document Neil, thank you!

 

[sq225917]

I guess we mean different things by cad boards. I'm talking about proper cad routed layout, not help with drawing curves in an early dtp package.

 

[booja30]

I think folks had been mentioning layout and consistency in traces. Clearly in the 72/olive era boards there is more consistent track width, separation, etc.

 

[nobeone]

I guess we mean different things by cad boards. I'm talking about proper cad routed layout, not help with drawing curves in an early dtp package.

Yes we are talking about different things, I was meaning simply a computer was used to do the layout, Computer Aided Design, you are talking about auto routing perhaps? Anyways, from my perspective booja is showing my interpretation of CAD and hand drawn

I would agree with colasblue on the difference being more for power amps with hand drawn curcuits, and since this is a pre amp thread my apologies if my previous comments knocked the thread off topic a little ...

 

[MJS]

Naim shifted to a number of CAD/CAM/CAT manufacturing techniques starting with the introduction of the Olive series. I know, I was there, programming first the insertion machine that stuffed the boards, and later the Teradyne testing system.

Same basic topology and new casework yes but as CAD design and Circuit Board manufacture technologies improved Naim moved from hand drawn single sided boards to CAD design, through hole and then full two layer boards. Whether that really resulted in any sonic improvement is anybody's guess.

The early hand-drawn amp boards definitely have a more relaxed and refined presentation. The CAD drawn amps sound a little more 3D in comparison.

 

[m3trackboy]

Thanks for all the comments really helpful.
Now for a newbie stupid question: what order does the signal go , is it TA > Gain stage > Buffer and what stages is the vol / balance control between?

 

[wylton]

most interesting - i remember demo-ing the 102 at a dealer and getting into a bit of an argument with the dealer over the fact that i thought my olive 62 sounded much better than the 102 - dealer contended it was quite impossible of course ... but this might explain why that was

I have a 102 and I prefer it to the 72 that I had previously, but I also like the 62 & the 42.5! I also have a 22 and a couple of 12's too, but I haven't found the time to test them yet. Based on other peoples experience the 12 should be good! the only thing I don't like about the older pre-amps is that they only have 3 x inputs.

 

[neiljadman]

...what order does the signal go , is it TA > Gain stage > Buffer and what stages is the vol / balance control between?

IIRC it's:

Input - Input selector switch - Input buffer (324 or 729s) - volume pot - balance pot - Gain circuit - delay relay - output

The tape output buffers take the signal from the input selector before they hit the input buffer.

 

[MJS]

As Neil says above, but low range pre-amps (NAC12,42,62,92) did not have a tape buffer. On those the switched input was routed directly to the tape output pins via 680R resistors before it got to the main buffer stage. Out of interest the Nait1 and 2 didn't even have a buffer circuit - the signal went straight into the gain stage.

 

[m3trackboy]

Thanks for the reply's
The 729's seem to be a Marmite circuit, some people absolutely hate them others love em!
At the moment i'm using a NAC92 which seems to be input buffer and gain stage but no TA's.
Not sure which way to go, a pair of Les W's boards or "convert" the input buffer into a TA on the 92. I had a quick look and I think there is enough room to shoehorn the required components in on the end of the buffers. Prefer to keep the 92 as the case is of similar proportions to the other kit. If I power each stage separately it should produce very respectable results. Although I enjoy the DIY side my main aim is to listen to the music!

 

[neiljadman]

As Neil says above, but low range pre-amps (NAC12,42,62,92) did not have a tape buffer. On those the switched input was routed directly to the tape output pins via 680R resistors before it got to the main buffer stage. Out of interest the Nait1 and 2 didn't even have a buffer circuit - the signal went straight into the gain stage.

Oddly I have always regarded those resistors as a very primitive buffer

And again IIRC, the gain stage is a simplified version of the 321 - having one fewer transistors in it.

... At the moment i'm using a NAC92 which seems to be input buffer and gain stage but no TA's.

Since the NAC90 is the front end of the NAIT3 this might be interesting...https://pinkfishmedia.net/forum/threads/fun-games-with-a-nait3.76926/

 

[Jonathan]

As Neil says above, but low range pre-amps (NAC12,42,62,92) did not have a tape buffer. On those the switched input was routed directly to the tape output pins via 680R resistors before it got to the main buffer stage. Out of interest the Nait1 and 2 didn't even have a buffer circuit - the signal went straight into the gain stage.

i would love it if someone might explain to me in real terms what having the tape buffer gets you ... as someone who has a few open reel decks it may be of interest

 

[neiljadman]

As I understand it (in layman's terms) it prevents the preamp section seeing any signal fluctuations/drain caused by tape deck, which could be audible. It works on the tape output only and isn't needed if you never use that output for any purpose.