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NAP 90 versus NAP 160

I quite agree. The ITT caps are 80 mm high with a diameter of 40 mm. You can now get a quality 10,000 uF, 40V capacitor in a 35 mm diameter can that's 35 mm tall. As near as damn it that's one third of the original volume.

But it doesn't alter my belief that throwing enormously large amounts of capacitance at a well-designed (in its day) power supply is not necessarily a good thing.
 
OP do bear in mind you'll be devaluing the 160 as soon as you take your soldering iron to it (even with the tiny solder burn to that wire I'd call yours an orig/ unmolested 160 there- ie I cant see any diy at all tbh). Fine if like mine (olive nap 140) if it was cheap & you know its a keeper though.

I might be inclined to try an olive nap 140 1st. I think you'll find it ticks all the boxes you're after, going from a nap 90 that is: a very old bolt-top 160 as it is, might not be quite the 'gem' the later cb ones can be (my later cb one certainly was).
 
Captain, that's a good point. The amp cost £275 and I can't tell if it's going to be a keeper until I've heard it working properly, which judging from the comments on here, it may not be. As I mentioned, it sounds good, but not much of an improvement on the 90.

If I get it properly serviced then it will owe me around £500 (?)

As long as I stay away from Johnny Blue's system, I wouldn't have thought I'd need to upgrade it, but then again, I think I could be heading down the slippery upgrade slope...
 
It's already been messed about with, as the thread to which I linked earlier makes clear, and others' observations on the photos point to the same thing. Let's get the best out of it with minimal investment...
 
Exactly. You'll always get this sort of reaction in the Audio forum.

We're not talking about mucking about with a 3 year old Aston Martin but rather about keeping a 35 year old Austin Maxi running as well as possible. Hence my carefully considered first post to the thread indicating how that could be achieved for around £35.

So Kim should end up with a £310 amplifier that will kick the backside of many a more modern device.

Last word of advice - stick with like-for-like (other than fitting higher voltage rated capacitors where appropriate) and you won't go far wrong.

Do let us know how it goes and don't forget to check what the output transistors are.

malcolm
 
misterc6 said:
Exactly. You'll always get this sort of reaction in the Audio forum.

We're not talking about mucking about with a 3 year old Aston Martin but rather about keeping a 35 year old Austin Maxi running as well as possible. Hence my carefully considered first post to the thread indicating how that could be achieved for around £35.

So Kim should end up with a £310 amplifier that will kick the backside of many a more modern device.

Last word of advice - stick with like-for-like (other than fitting higher voltage rated capacitors where appropriate) and you won't go far wrong.

Do let us know how it goes and don't forget to check what the output transistors are.

malcolm
Click to expand...

You've hit on the perfect analogy for Kim, he loves his motors!
 
The transformer/bridge rectifier arrangement is apparently wrong. There should be two, half of each being used, bolted cases amps usually have 4 discrete power diodes, as in the CJ photos. This is a mystery, because the implication is that there's an unused transformer winding somewhere.

If this amp is configured as Naim built it then it's very rare.

The preamp PSU is also unusually arranged, although the wiring colours match other amps.

Worth investigating by someone who knows what they're doing.

Paul
 
Ok let's say it has been tinkered with then- OP how was it sold to you, as 100% orig? or having been tinkered with? it certainly shouldn't have been sold as orig, if Paul Ranson et al are correct which I wouldn't disagree with in retrospect, and as you paid £275 that's spot-on (actually twds top £ tbh) for an unmolested bolt-top nap 160. Id have thought it was, in fact worth £150 ish in tinkered-with condition. I just hope it wasn't sold on pfm as orig then..
 
Paul Ranson said:
The transformer/bridge rectifier arrangement is apparently wrong. There should be two, half of each being used, bolted cases amps usually have 4 discrete power diodes, as in the CJ photos. This is a mystery, because the implication is that there's an unused transformer winding somewhere.

If this amp is configured as Naim built it then it's very rare.

The preamp PSU is also unusually arranged, although the wiring colours match other amps.

Worth investigating by someone who knows what they're doing.

Paul
Click to expand...

I understand what you are saying Paul and this is the first block bridge rectifier that I've seen in a 160. And also the first with a PAPS1 regulator board rather than a simple three terminal regulator. However I come back to the point that the dividing screen is not drilled for four diodes and it seems unlikely that any 'bodger' would replace the screen.

Turning to your point about the transformer/bridge rectifier arrangement I think you may be confusing the 160 which I believe is a perfectly standard arrangement with what is found in the 250 bolt down.

Take a look at the first photo here:

http://picasaweb.google.com/misterc6mg/NAP160?feat=directlink

I believe this comes from a totally original bolt-down 160. The four diodes are arranged as a normal bridge rectifier. On the amplifier side of the screen the two cathodes are connected together and go to the positive rail. Similarly the two anodes are connected together and go to the negative rail.

On the power supply side of the screen you can see the three wires from the main centre-tapped secondary of the transformer. The colour coding is strange but the ends of the winding are green/yellow and yellow and each goes to opposite nodes of the bridge rectifier. The centre-tap of the winding is green and goes to the earth point at the junction of the two large caps. This is the normal arrangement for getting positive and negative power rails. The two grey wires from the positive side capacitor go back to the bulb in the power switch.

Additionally the transformer has a smaller secondary for the pre-amp supply - the two orange wires connected to the small bridge rectifier on top of the 3,300 uF capacitor.

If you flick through to the third picture which I believe to be an 160 that seen a straight forward capacitor replacement service you'll see that the arrangement is also a standard bridge rectifier for a centre tapped secondary although the cable colours are different. In this picture you can also just see the standard three-pin regulator for the pre-amp supply.

Turning to the photos of the OP's amplifier the arrangement is exactly the same except that the four diodes are encapsulated in one block, the three-pin regulator has been replaced by a PAPS1 and the power feed back to the power button illumination is missing. Many users disabled the bulb for sonic reasons anyway. I do agree that this is unlike any other bolt-down 160 I've seen but the lack of other holes in the dividing screen convinces me that it must have been manufactured this way.

malcolm

p.s. I suppose this arrangement should be referred to as Full Wave Rectification rather than Full Wave Bridge Rectification see: http://www.play-hookey.com/ac_theory/ps_rectifiers.html
 
You're quite possibly right, and that would follow with the extruded case version having two sets of reservoirs for the power amp but only two bridge rectifiers.

So it's likely this is a very late bolted case NAP160, overlapping at least with the NAP110.

Paul
 
The Captain said:
Ok let's say it has been tinkered with then- OP how was it sold to you, as 100% orig? or having been tinkered with? it certainly shouldn't have been sold as orig,
Click to expand...

From the Fleabay ad:

For Sale - My Naim Nap 160 Power Amp. This amplifier is over 20 years old, It has been in my loft unused for 10 years I had forgotten I had it. Ive tested the amp and it sounds brilliant, Ive heard that there is plenty of upgrades for this amp, It has never been touched so there is plenty of scope for the winning bidder to further improve the sound quality of this great amp.
 
hollamby said:
From the Fleabay ad:

For Sale - My Naim Nap 160 Power Amp. This amplifier is over 20 years old, It has been in my loft unused for 10 years I had forgotten I had it. Ive tested the amp and it sounds brilliant, Ive heard that there is plenty of upgrades for this amp, It has never been touched so there is plenty of scope for the winning bidder to further improve the sound quality of this great amp.
Click to expand...

Well, we know that's clearly untrue, don't we!
 
It's more like 30 years old.

It may improve with time as the caps come back to life.

But the £35 refresh discussed up thread is the way to go. IMO.

If it sounds OK now perhaps use it for a while and see.

Paul
 
There are photos of NAP110s that show the hardwired preamp PSU arrangement, and then others with a small PCB. Both these examples had blue ITT type reservoir and protruding speaker connectors.

So I think this is a very late NAP160, somewhere between the arrival of the NAP110 in the extruded case and the move of the power amps to the full width extruded cases. An interesting bit of history.

Serial numbers would be informative, perhaps this is an 'employee build' of some form.

Paul
 
I think for the OP its well worth taking stock getting the final answer 1st as to if it IS orig, or has been tinkered with (its still unclear, I'd be surprised tho if it wasn't as it was originally even with this mystery 'extra board', but that's just my opinion).

So email naim, or phone naim/ Sheila with its seriel no. Ask if there were any slight internal layout differences in nap 160's.
 
The one that CJ has pictured above is serial number 2006.

I believe that it was well after this time that Naim adopted the sequential numbering scheme where two consecutive numbers could be entirely different products and when I e-mailed Naim that said that their records did not go back this far. So there could be anything from none to 134 NAP160s between the two serial numbers.

I had also considered it being an employee build, but they normally have no serial number.

malcolm
 
Quick question: can I assume the V rating for the tant caps is as flexible as for the big electrolytics.

Zener has very helpfully supplied Farnell part numbers, but the 100uf 6v tants are US stock only (extra £15+ shipping, plus volcanic ash delays). Will the 10V version be OK?
 
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