NAC 92 maiden voyage into mod land

[nickcase]

Thanks David

I've swapped the 10u output SMRs for Silmics. The difference is enormous, smoother and warmer but also more muddied.

We'll see how the sound changes over the next two weeks, the previous Silmics I used sounded rubbish for at least a week before livening up.

Frank, you mentioned replacing the tants in the PA was a big improvement for you. I've not had a detailed look inside a Naim PA (mines a 180) is there a thread on this somewhere or are these tants obvious?

Nick

 

[Anderzander]

I'd be interested in this too

When I looked in my 140 there did appear to be a load of BC128 candidates

 

[fatcat]

In the picture below.

Top right orange tant. 10uf/35V Coupling
Bottom two orange tants. 10uf/35V SAO circuit.
I have removed the SAO circuit as recommended by LesW

Top left plum tant 47uf/6v Feedback.
(From memory I think the feedback cap is in series with a 1K resistor)
Bottom right plum tant 47uf/6v (not got a clue what this is).


In my ageing 110, I found replacing the coupling tants with a new tant the key.

See thread.
http://www.pinkfishmedia.net/forum/showthread.php?s=&threadid=11522&highlight=tant

Nick.
Your feedback cap may be 100uf. I have read a thread that indicates Naim now use 2x47uf instead of 100uf in the lager amps.

Anders
If you don't try tants first, you wont hear how Naim intended your 140 to sound.

 

[nickcase]

Thanks Frank, I'll take a look inside my "lager" amp tomorrow, hopefully I won't find any ringpulls or football hooligans

 

[fatcat]

Originally posted by nickcase
Thanks Frank, I'll take a look inside my "lager" amp tomorrow, hopefully I won't find any ringpulls or football hooligans

A Freudian slip. I’m glad Mus didn’t notice it, he thinks I'm a bit of a lush.

 

[nickcase]

Frank

Your feedback cap may be 100uf.

Nothing greater than 47uF.

See picture - 3 Blue 10u tants and 3 plum/red 47u tants. The other 4 caps are 470pF , polystyrene I assume.

I've mislaid my small hex bits so I couldn't get the board out tonight to trace tracks.

I'm not familiar with the circuit, any advice on what is what here?

 

[fatcat]

Nick

The 2 plum 47uf next to each other may be in parallel giving an effective feedback cap value of 94uf. (2 caps are probably bitter than 1, in lager amps)

The 1 plum on its own is the one I don’t know what it does.

Top right blue is coupling

Bottom pair of blue SOA.

As you have blue caps in there they may not be very old.

 

[Anderzander]

to compare here's a 140

 

[fatcat]

Put the 10uf SRM’s in the buffer outputs last weekend. Didn’t like them at all. Bass and mid/bass disappeared, music lifeless, timing went AWOL.

Today. Tants went back in. Very happy again.

 

[Basil]

Fatcat,

According to the "Naim Preamp Mods and Upgrades" section at acoustica, you should only use SMR's on the inputs.

 

[Linnik]

Hi Anderzander & al,

Those bolts and nuts of the transistors would be quite easy to change for stainless steel hexagonals. Both the smaller ones on the board and the power transtrs.
And it will sound better again..

Cheers,

Oz