Hi ! Here is a nap300 build I just completed for a friend. He gave me acces to a few pairs of original nap250 boards and asked me to build him an amp around the only pair of nap300 boards he had. Given the price of these amps on the new market, I couldn’t say no. (Free projects, why would I say no anyway) it has two 500va transformers that were made for Cambridge 650r receicers and a total of 80000uf. anyway, that is the story behind the build. I still have two other build to complete with nap250 boards.
So here is my question. I don’t have access to the service manual or even a schematic for the nap300. I have set the bias to 9mv across both 22r emiter resistors according to the information i’ve found on the internet. DC offset is damn near perfect at 1mV on both channels. BUT, there’s two more pots on each boards that are still unused (by me). My guess is that they are used to set the rail’s voltage, but I don’t know what voltage to set it and where to measure it. Does anyone have information about this ? Thanks !
btw, it sounds incredible. Very detailed but smooth at the same time. Really good match with my series 80 B&W 802 ! The clear cover is only temporary…
So here is my question. I don’t have access to the service manual or even a schematic for the nap300. I have set the bias to 9mv across both 22r emiter resistors according to the information i’ve found on the internet. DC offset is damn near perfect at 1mV on both channels. BUT, there’s two more pots on each boards that are still unused (by me). My guess is that they are used to set the rail’s voltage, but I don’t know what voltage to set it and where to measure it. Does anyone have information about this ? Thanks !
btw, it sounds incredible. Very detailed but smooth at the same time. Really good match with my series 80 B&W 802 ! The clear cover is only temporary…
Last edited:
Nice work! To meet NAP300 specs of 90WPC/8R though, you would likely have needed higher than nominal +/-40V regulated PSUs. In the process of assembly, you could also have traced some of the schematic details and differences to widely known and published models like NAP250, for example, from examining the boards and connection details.
Parts details aren't shown on any printed overlay but I think you must know more than said so far, about NAP 300. Why not share the relevant design details that would make your assembly work and valuable contribution to our limited (also near zero?) knowledge of the product something we can follow and understand. Perhaps then we can offer at least some help on setting close, if not absolutely correct rail voltages. 'question is though; within sensible limits, does it really matter if they're not absolutely correct for a clone?
Parts details aren't shown on any printed overlay but I think you must know more than said so far, about NAP 300. Why not share the relevant design details that would make your assembly work and valuable contribution to our limited (also near zero?) knowledge of the product something we can follow and understand. Perhaps then we can offer at least some help on setting close, if not absolutely correct rail voltages. 'question is though; within sensible limits, does it really matter if they're not absolutely correct for a clone?
Last edited:
From the information I have, the boards should be supplied +\-52v. They get the supply that the trannys/psu I built can provide, i just don’t remember the exact values. I gave back the amp to it’s owner as is since it played really well and nothing seemed wrong about it. Can we really call this a clone when the boards are original ones ? 😅
i will be able to share a bit more information when i build my own nap250dr. Still have 3 pairs of 250dr boards in their original naim boxes and full original documentation and schematics for them. Not shure if i’d share everything for obvious reasons. These things aren’t supposed to be public…
from what I understand, the nap300 and nap250 are very similar. Same output devices, same input impedance. The only significant difference is the regulator. The 300 is built into two boxes, but in reality the power supply box is pretty much empty. It looks pretty much like the upgraded psu you can get for any naim product (hicap, etc). The 300 boards are bigger and have more parts mostly because of the regulator as far as I know. The 10w difference is only a rail voltage/bias difference. Not really a circuit difference.
i will be able to share a bit more information when i build my own nap250dr. Still have 3 pairs of 250dr boards in their original naim boxes and full original documentation and schematics for them. Not shure if i’d share everything for obvious reasons. These things aren’t supposed to be public…
from what I understand, the nap300 and nap250 are very similar. Same output devices, same input impedance. The only significant difference is the regulator. The 300 is built into two boxes, but in reality the power supply box is pretty much empty. It looks pretty much like the upgraded psu you can get for any naim product (hicap, etc). The 300 boards are bigger and have more parts mostly because of the regulator as far as I know. The 10w difference is only a rail voltage/bias difference. Not really a circuit difference.
Attachments
Last edited:
A friend want to replace the main elcaps in the PS for NAP300 - go to the attached images No 1+2.
Service manual and schematics are not online for download.
What is the aim of the parts (several small signal transistors and resistors) close to the BHC elcap quartet on that PCB ?
Maybe a control unit for the relay on the inrush limiter unit on right edge close to the IEC plug ?
Best thanks for an information.
Service manual and schematics are not online for download.
What is the aim of the parts (several small signal transistors and resistors) close to the BHC elcap quartet on that PCB ?
Maybe a control unit for the relay on the inrush limiter unit on right edge close to the IEC plug ?
Best thanks for an information.
Attachments
Could be a discharge circuit...
See also here:
https://pinkfishmedia.net/forum/threads/555ps-dr-towering-inferno-–-resistor-values-needed-please.254206/
See also here:
https://pinkfishmedia.net/forum/threads/555ps-dr-towering-inferno-–-resistor-values-needed-please.254206/
