NAP 250 experience
I just had some NAP250 boards made at JLC. I saw this french guy's video about his build on youtube. I asked him if he would share his gerbers and he said ok. My second NAP 250 clone - YouTube This is the first naim related product i've ever heard. I'm very impressed. I used some transformers from a NAD 2140 i parted out, and a case from an carvin bass amp someone gave me. heatsink is a big chunk of aluminum and fins on underside.
I just had some NAP250 boards made at JLC. I saw this french guy's video about his build on youtube. I asked him if he would share his gerbers and he said ok. My second NAP 250 clone - YouTube This is the first naim related product i've ever heard. I'm very impressed. I used some transformers from a NAD 2140 i parted out, and a case from an carvin bass amp someone gave me. heatsink is a big chunk of aluminum and fins on underside.
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Cool! How does it sound??? I just swapped my 2N5551 in the Vbe spreader for a vintage ZTX108C and can say it sounds much nicer (less sharp and bouncier). I have the feeling that all parts could change the sound, and I am not so sure about having films in place of styrenes (and lytics instead of tants). I bought my styrenes here:
Mouser
Farnell
Hificollective
Don Audio
Audiophonics
Mouser
Farnell
Hificollective
Don Audio
Audiophonics
Well i have zero experience with naim, and that box of stuff i threw together probably has very little relation to the real vintage amps. I can however get a feeling for what naim was going for based on the wide all encompasing sound characteristics that are derived from the circuit, and power regulation, which is not very common.. I've been in the midfi zone for a couple years and this amp made sure i'll never go back. The nimble pace and effortless wide detailed soundstage was simply outstanding. The bass was instantly so much better, better at giving dimension to the notes, better at separation, better control. simply outstanding. The rich beautiful mids and highs were gorgeous, female voices especially, outstanding. Based on my jalope, however far from the real thing, gave me a lot of respect for naim. I just built a pass f6 and i'm getting blown away in a similar way right now
I am glad you like the Naim style. In my ears Naim can best deliver the communicating aspects of music. Music speaks, sings, tells, touches. These things are the most important in my view and are intact with Naim.
I would be very interested to hear more about the differences between your NAP clone and the Pass!
Regarding the boards your are welcome to contact me by pm.
I would be very interested to hear more about the differences between your NAP clone and the Pass!
Regarding the boards your are welcome to contact me by pm.
Thanks! I made a version for plastic output devices and added 100R resistors (with solder jumpers to short them out) to the LTP in case BC546 is used instead of BC239. The TO92s in the LTP are placed so that they could be thermally coupled. Also I put the ZTX108 near the driver heatink so it could be thermally coupled to it as in the early NAP160. I kept the trace from TR2 short as was suggested earlier in this thread. What else can be done?
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Thanks! Even more beautiful with MJL3281s (shorter traces at the output devices):
And here a parallel output version (if we use BUV20s why not):
Question: will the MJL3281s behave well with the MJE243/253, or should I combine them with their stablemates MJE15032/33 as Neil McBride suggests?
And here a parallel output version (if we use BUV20s why not):
Question: will the MJL3281s behave well with the MJE243/253, or should I combine them with their stablemates MJE15032/33 as Neil McBride suggests?
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For the poor or profane
I am planning my next build and the issue of finding a suitable case took up a couple hours of my day today. I really don't want to spend a couple hundred bucks on a new empty box so i did some clicking. The best solution i found was to repurpose a pro-audio box from a "AMX Axcent 3 PRO Integrated Axxess ControlFrame" It is all aluminum, and is 3.47" x 17.0" x 13.65" (88.1 mm x 432 mm x 356.8 mm) close to the dimensions of the ebay boxes made for NAP250. There are some holes and slots on both the front and back that need to be either bondo'd or simply covered my screwing an aluminum plate over the whole area. I bought one today on ebay for $25 including delivery. There was one on craigslist but the guy wanted $30. There seems to be many offered on ebay from $25 to $50 or so.
Has anyone else found a better solution in the $50 zone?
Making Money Scrapping An AMX AXCENT PRO For Aluminum & Gold Boards! - YouTube
I am planning my next build and the issue of finding a suitable case took up a couple hours of my day today. I really don't want to spend a couple hundred bucks on a new empty box so i did some clicking. The best solution i found was to repurpose a pro-audio box from a "AMX Axcent 3 PRO Integrated Axxess ControlFrame" It is all aluminum, and is 3.47" x 17.0" x 13.65" (88.1 mm x 432 mm x 356.8 mm) close to the dimensions of the ebay boxes made for NAP250. There are some holes and slots on both the front and back that need to be either bondo'd or simply covered my screwing an aluminum plate over the whole area. I bought one today on ebay for $25 including delivery. There was one on craigslist but the guy wanted $30. There seems to be many offered on ebay from $25 to $50 or so.
Has anyone else found a better solution in the $50 zone?
Making Money Scrapping An AMX AXCENT PRO For Aluminum & Gold Boards! - YouTube
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Definately double front and back with aluminum, you can use it as heat sink for the power devices if you bolt parts like this to it (I used these, see earlier in this thread). Keep in mind that the NAP case should hold the air temperature around the transistors constant.
@JeffYoung, just to make sure as most sources quote 7mV for a standard NAP250 across both emitter resistors: am I missing something?
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@JeffYoung, I just checked what I can find regarding bias on NAP circuits, here some links:
Neil McBride describes setting bias by measuring voltage across the 0R22 emitter resistor at the positive power transistor and recommends 4.4~6.6mV
Acoustica.org recommends 4.5mV across the positive resistor and 8.0~8.9mV across both resistors.
NAP135 servicing thread on PFM states 7.0mV across both resistors.
Bias measuring thread on PFM discusses measuring in cold or warm state and agrees on ~7mV across both resistors.
The latest HackerNAP build instruction recommends 3~5mV after warm up and warns that bad things can happen above 6~7mV.
Neil McBride describes setting bias by measuring voltage across the 0R22 emitter resistor at the positive power transistor and recommends 4.4~6.6mV
Acoustica.org recommends 4.5mV across the positive resistor and 8.0~8.9mV across both resistors.
NAP135 servicing thread on PFM states 7.0mV across both resistors.
Bias measuring thread on PFM discusses measuring in cold or warm state and agrees on ~7mV across both resistors.
The latest HackerNAP build instruction recommends 3~5mV after warm up and warns that bad things can happen above 6~7mV.
My original interpretation was also 7mV across both, but someone who I trust said no, it's 14 across both together. I can't remember who it was, though. Probably either Les @ Avondale, Ian from PFM, or TraderBam. I can't think of anyone else I would have accepted without further question.
Hmm... there was also the tech who used to work at Naim. Could have been him too, but I can't ever remember his name....
Fat lot of use I am, huh?
Hmm... there was also the tech who used to work at Naim. Could have been him too, but I can't ever remember his name....
Fat lot of use I am, huh?
You did help more than a lot until now, many thanks! I designed cases for the NAP, see pictures below: one has the power transistors outside on these heatsinks, the other one has them inside, mounted on L-profiles which are attached to these even heavier heatsinks. So lighter heatsinks with the transistors directly sitting on them or heavier heatsinks but with the heat redirected through L-profiles: which version is better?
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