Out of curiosity I recently moved my second HiCap DR from the SuperLine to “upgrade 2” at the rear of my Nac 282 resulting in the SL being powered by the AUX2 power output on my now dual-HiCap NAC 282. I was genuinely surprised how well it performs in this configuration, to my ears, vinyl sounded better with more grip and authority and there was also a noticeable uplift (again to my ears) to the NDX2 and CD5Si. As a result, I have retained the second HiCap DR powering the 282.
This has caused me to wonder how the AUX2 implementation differs between the 282 and the 252. I’ve found posts by Richard Dane stating that the 282 AUX2 is not fed from dedicated transformer windings, whereas the 252 AUX2 is fed from dedicated windings and regulators on the SuperCap.
My question is simply: what is the architectural difference? As far as can be discussed publicly:
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How is the AUX2 power derived on the 282 compared with the 252?
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Are the 252 AUX2 regulators dedicated to the SuperLine, or shared with parts of the preamp?
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Is there any published information or block diagram showing the topology?
I’m not looking for advice on the best way to power a SuperLine, nor am I comparing the sonic merits of different power supply options. My curiosity is purely about the engineering differences between the AUX2 implementation on the NAC 282 and the NAC 252.
Thank you in advance for any information shared.
On the 282, depending on the power supply configuration you are using (single rail, 2 rails, 4 rails), you tend to be sharing the aux2 rails with other parts of the preamp. If you were using a Supercap or dual Hicaps to give 4 power rails with both upgrade 1 and 2 sockets being used then quoting the faq here for when all 4 rails are used…
Upgrade 1 socket powers the left channel: 729 input filter stage and tape buffer off one regulator. This regulator also powers one side of the aux2 output (for the right channel of a stageline), gain stage off the other regulator
Upgrade 2 socket powers the right channel: 729 input filter stage and tape buffer off one regulator. This regulator also powers the other side of the aux2 output (for the left channel of a stageline), gain stage off the other regulator
With a 252, you are connected to the Supercap via a Burndy cable and this provides two dedicated rails directly from the Supercap to the aux2 socket. Nothing else in the preamp utilises these rails.
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Thank you so much for such a knowledgeable and concise response 
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Thanks, but kudos really to Richard for getting the definitive answer from Naim R&D as to how the various parts of the 282 (and 82) are powered in dual power supply (4 rail) configuration.
A subject of much debate on here over the years.
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I somehow managed to have 3 HCdrs with my 282 and superline. To be fair I couldn’t hear a difference with the dedicated HC on the SL.
The extra buggeration and no difference in sound had me sell the extra HC. By this point naim had stopped selling them, so I actually made money selling it. Enough, that I bought a pre owned supercap to replace the two HCs. Tye SCdr made no difference in sound to me, and if honest I think the two HCs were better on the 282, but that’s another well trodden debate. But a look inside the HC and the SC and you may see why two HCs should sound better.
Anyway, as always a SC on a 282 tends to lead in one direction only. And one that saw me sell off my final two HCs.
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No need to ask which direction that went. 
Were you pleased with the 252?
Haha, yes and yes. As always I bought pre owned for a good price and near mint condition; not bad for a 2003 model. Full and first service back at naim. Cant say i heard any sound improvements, but I got peace of mind. The pot was changed due to the usual imbalance at low volume issues for one that was pretty similarly not great ! And as moaned previously naim failed to rectify an original build sin- id taken internal phots pre and post service for curiosity.
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