Great, thanks HH. Quite a short list in the end. Never heard of the 145 before.
Basically, anything related to the 250, is a regulated design. Guess we should include its predecessor, the original 200…? Not sure… 135 & 300 definitely - as direct 250 derivatives. I believe the 500 is effectively a bridged 250…?
Am sure @Richard.Dane can confirm, for us.
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The NAP-V145 was a single channel version of the NAP250.2, intended for AV use.
Yes, the original NAP200 was the first regulated amp, and this was then developed into the NAP250.
I’d forgotten the original 200. Do you know how the NAB 300 fitted in? And NAB rather than NAP, do I recall it was a BBC specific amp?
The NAB300 was a professional version of the NAP250 for studio use. It used similar amp and reg boards but balanced input and frame transformer. According to Naim it didn’t sound as good as a regular NAP250.
Thanks Richard. Was it therefore B for Broadcast?
Possibly, or B for balanced.
I bet that was jolly good for its day
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That is the first time I have seen a picture of the NAB300, other than in the Naim catalogue.
Thank you, Harry… 
Wow!!! 
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Here are a couple more, one with lower capacity reservoir caps.
Fun fact - the rear fan is rated at 240V & runs at full tilt all the time.
Regards
Neil.
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There’s definitely something very cool about them, the power amp PCBs are hidden away within the heatsink.
Regards
Neil.
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Looking at the 3 posted, I can see clear detail differences between each of them. The Cap size clearly, but also the wiring. The ‘Choc Block’ is missing from No.3 (the small Cap version) and the wiring routing is different in each example.
From what I can make out there is a ceramic resistor by the fuses that then feeds the fan?
In the last photo you’ve posted it looks like 2 resistors and a switch at the other end of the back panel for “two stage” cooling
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Hi Richard,
I can’t be sure, as I haven’t looked inside a NAB300 for many years, but I think the thing(s) by the fuses are mains filter capacitors & the switch modification looks to be in the earthing - possibly to alleviate a hum loop?
Regards
Neil.
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Okay I think I know the difference between regulated and unregulated PS in theory but what’s the difference in audio terms?