NAP250 clone

[traderbam]

I was trying to be subtle but it seems I failed. Anyway, what's your take on the purpose of C7 there?

I don't know what subtlety is, lol. C7 is there to stabilize the bias circuit as you know but Naim puts it between C & E.

 

[traderbam]

Ian, collector-follower topology...what do you think?

 

[Ian Finch]

I simply don't think well as I nearly freeze here but I have assumed C7 is just an oversized signal bypass cap. applied along the lines of Self's model blameless design. Often it's a smaller film cap. but nothing surprises me for JV's designs. This isn't his baby, it's 250.2 though. Perhaps someone with access to Steve Sells' previous work at Roksan and elsewhere has a hint of where this comes from, if not a error by the reverse engineer, who could be D. Albert or @Leo, not a Chinese reverse engineer, since hifidiy.net usually just watermarks and posts other people's work from the net .

 

[Oleg Turbin]

If you can make a working DR schematic please post here, or at least PM me :круто:

Attached new NAP250 schematics, reverse engineered by a member of a chinese forum:

Good day Dear JPK this is NAP250.2 schematics of China nap250.2 clone supplier add this schematics with boards in attachment photos (with mistakes in roads hhhhhh).
Buy this and you need wire …. Wire? Why wire? Aaaaaa …how to much ??? Wireeee… )))
Also I think this first amp by Steve Sels design )) (many many many current sources …) after that new Naim designers make 250DR amp…

 

[jpk73]

I attach some NAP300 DR and non-DR pictures, maybe it helps as well:

 

[jpk73]

NAP500 (I would love to see a non-DR schematic):

 

[jpk73]

more:

 

[jpk73]

A NAP250DR diagram, taken from some Naim whitepaper, and 2 diagrams about the NAP500 (totally guess work): I am not sure about the PDIP8 in the middle, maybe it's a phase splitter, or some protection circuit...?

 

[jpk73]

Some NAP135 pictures:

 

[jpk73]

...and regarding C7: here some schematics of other Naim amps:

 

[jpk73]

Finally, just in case, probably not needed, but PCB pictures of original NAP250 boards:

 

[traderbam]

Thanks JPK73!

 

[Oleg Turbin]

Finally, just in case, probably not needed, but PCB pictures of original NAP250 boards:

Nice work Jpk73!!! Thanks!!!

 

[traderbam]

I simply don't think well as I nearly freeze here but I have assumed C7 is just an oversized signal bypass cap. applied along the lines of Self's model blameless design. Often it's a smaller film cap. but nothing surprises me for JV's designs. This isn't his baby, it's 250.2 though. Perhaps someone with access to Steve Sells' previous work at Roksan and elsewhere has a hint of where this comes from, if not a error by the reverse engineer, who could be D. Albert or @Leo, not a Chinese reverse engineer, since hifidiy.net usually just watermarks and posts other people's work from the net .

The NAP300 photo also shows C7 in a different place, as does the Nait5i.
I didn’t know Sells worked at Roksan.
As we have commented in the past, Sells appears to have lost/discarded the original recipe. Not good.

 

[jpk73]

Hence I am most interested in a non-DR NAP500. It seems to me the 500 has 250/300-like main boards with the added circuit around the PDIP8 in the center, plus the smaller middle PCBs, plus a fan like the 135. So are we able to put together a NAP500 clone...?

 

[traderbam]

The 500 has two amps in bridge mode, each with a regulator, per channel. 16 power transistors in total. Perhaps like a bridged 135.

 

[Ian Finch]

I've been poring over the XS2 schematic posted earlier (thanks indeed, jpk, you've shed light where there was darkness!) and that really surprised me. l've seen a few unusual topologies but that one has me stumped. Is it a "clever clogs" tech idea that didn't really sing or dance or is it a cinderella waiting for someone to slap on the makeup and hairdo, teach a few moves and presto! A star performer is (re)born?

As it stands, I understand XS is not exactly a popular line but what does that matter to Naim fans? They'll enthuse and slaver over the brand name regardless of what's inside or should that be "not inside"

 

[Oleg Turbin]

The NAP300 photo also shows C7 in a different place, as does the Nait5i.
I didn’t know Sells worked at Roksan.
As we have commented in the past, Sells appears to have lost/discarded the original recipe. Not good.

Yes dear Steve permit only “Steve design” in all Naim amps but old design it’s Julian Vereker ideas and music soul
please see photos of old board nap 250 published by jpk73 and you watch soul design
If I working in Naim Audio I will changed of all new Naim amps And change all design of all amps and preamps boards … but I go to another way with my teacher Julian Wereker
Very interesting somebody in Naim Audio designers read this forum or not ? Hhhhhh ))

 

[jpk73]

I own a Supernait v1, I guess it is practically an XS with a larger PSU plus a DAC and preamp and rec-out etc., but it sounds typical Naim and very good indeed (I prefer the Supernait to the Avondale NCC300 BTW). I owned NAP90, NAP135 (both passive and 6* active into NBLs), NAP500 in the past and can tell that the 500 is a totally different beast (it outperformend the active setup by far). Stupid me that I didn't open it and took pics before I had to sell it, but at that time I wasn't into diy yet...

 

[jpk73]

The 500 has two amps in bridge mode, each with a regulator, per channel. 16 power transistors in total. Perhaps like a bridged 135.

I am not so sure if it's just a bridged 135. There might be more into it...