72 vs 32.5 question

Hi-Fi Corner
1

Say you have a serviced 72 and an unserviced 32.5. Can you drop the 72 boards into the 32.5, and suddenly you more or less have a serviced 32.5?

I recognize that would not cover all the potential service requirements, but maybe it’d be pretty close?

2

One for @Richard.Dane or @NeilS , methinks… :thinking:

3

There’s certainly a lot that’s similar, and in most cases the boards can be swapped directly. However, with essentially two versions to the NAC72, there may be an issue (possibly with the NA729s?). I don’t know for sure where, but I’m sure @NeilS can enlighten us.

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4

I am under the impression that a large part of Naim equipment servicing is replacing any worn out capacitors (‘recapping’). You won’t achieve that by installing input boards from another preamp.

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5

2 versions? Is this because of the use of 329? or 324 boards, or something else?

6

Im not sure there is anything on the main board that gets changed. All the caps that are changed i think are on the daughter boards.

7

Yes. The first version of the 72 has 2 pair of BNC input - one marked Phono and the other marked Aux (which usually had the 328 V variable line level boards fitted). The 2nd version has just one set of BNC’s - for Phono. There is another DIN input instead of the 2nd set of BNC’s - which is now ‘direct’ (no boards involved) - marked CD (!!).

I have owned both versions… :grimacing:

8

With the NAC32 and NAC72, pretty much all the circuitry is on daughter boards, so it is possible to just swap out old boards for newly serviced ones. Of course that won’t fix any other issues there may be with things like the pots, switches or socketry.

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9

Thank you, Richard. That’s my lesson for the day, and it’s not even ten o’clock.

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10

Ah, that bit i thought i knew. It was the alterative daughter boards that i thought may have created the 2nd version.

11

Then what happens to the 72? Are you going to use if as a doorstop?

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12

AFAIK, it was the change to the input configuration - which probably meant a different main PCB.

13

It was this bit in the FAQ that caught my eye.
" NA329 - Time-aligned input buffer boards (similar to NA729), retrofittable for upgrade by replacing the input pair of NA324s x 2 "

14

Just a stopgap solution for the 32.5 until getting it serviced

15

Seem to recall you can use the 729 in a NAC 32.5 - it’s just that the balance control won’t work.

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16

To answer the OP’s original question, yes you can use the 72 boards in a 32.
The 729 was used in the 72 & the 329 the 32 - same PCB, but the 329 has a couple more components fitted to facilitate the mono/stereo function.
So the 32’s mono/stereo switch will have no function with 729s fitted.
Easy way to tell them apart:
729 = 4 gold receptacles.
329 = 5 gold receptacles.

Regards
Neil.

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17

Thank you Neil!

18

Thanks Neil, I knew there was some issue here with the NA729s and thanks for confirming that you lose the mono function, with 729s against 324s or 329s

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19

Are the 329 boards still available?

20

I don’t think any of the NA3xx boards have been made by Naim for many years.

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