it's a shame that you live on the other side of the planet because I recommend toroidiy transfos!
their quality is excellent and they have an internal screen that makes them perfectly silent even with sensitive circuits
Transformatory toroidalne - Producent transformatorow Toroidy.pl
their quality is excellent and they have an internal screen that makes them perfectly silent even with sensitive circuits
Transformatory toroidalne - Producent transformatorow Toroidy.pl
A bigger problem is that a custom transformer is needed for NAP200. I think this would cost quite a lot from a European manufacturer. When the NAP 200 kits were first shown here, guys were having to order their 400VA transformers from local manufacturers to get the two 2 centre-tapped secondary windings required for a clone build but keep freight costs down. A screen costs almost nothing to fit but the charges for such options can add up to unbelievable totals in one-off quantity.
Quite a lot of high-end amplifiers have been using dual mono construction for many years. Stereo systems need it to give optimum stereo performance - an added cost but much cheaper than two monobloc power amplifiers.
Most commercial audio products have some type of custom power transformer and the cost of more secondary windings isn't great in large quantity. Normally, a dual mono build is simply done with 2 smaller toroids each having a standard, dual secondary winding. For example, you might use a 300VA transformer for a normal 100W stereo amplifier but when constructed as dual mono amplifier, 2 x 160VA transformers would be used and the amplifiers finished as separate, electrically isolated amplifiers in the same case. There is an exception to full isolation which has to be in the grounding of both amplifiers to the case. This is a legal requirement in many countries.
The NAP 200 PCB has dual, separately laid out power supplies, one for each channel but their departure from dual mono principles is to use a single transformer having both sets of secondary windings on the same core. Some criticise this type of power supply because the windings are still magnetically coupled and hence not fully isolated in the way dual transformers would make them.
It might be interesting to check whether you could hear some difference if dual transformers were used but the size of the PCB and the cutaway for a single large toroid
makes this a very difficult thing to try in the appropriate case size.
Most commercial audio products have some type of custom power transformer and the cost of more secondary windings isn't great in large quantity. Normally, a dual mono build is simply done with 2 smaller toroids each having a standard, dual secondary winding. For example, you might use a 300VA transformer for a normal 100W stereo amplifier but when constructed as dual mono amplifier, 2 x 160VA transformers would be used and the amplifiers finished as separate, electrically isolated amplifiers in the same case. There is an exception to full isolation which has to be in the grounding of both amplifiers to the case. This is a legal requirement in many countries.
The NAP 200 PCB has dual, separately laid out power supplies, one for each channel but their departure from dual mono principles is to use a single transformer having both sets of secondary windings on the same core. Some criticise this type of power supply because the windings are still magnetically coupled and hence not fully isolated in the way dual transformers would make them.
It might be interesting to check whether you could hear some difference if dual transformers were used but the size of the PCB and the cutaway for a single large toroid
makes this a very difficult thing to try in the appropriate case size.
ok, nothing new to me then.
I had an interesting experience qlqs years ago with a dual mono amp.
two switches, two transformer, two pcb, two for cinch etc etc etc.
the amp worked perfectly if I operated one side at a time or if I plugged two different sources on each of the inputs.
but if I plugged a single stereo source on each of the two channels, a track between the two volume potentiometers went up in smoke and the fuses were blowing.
I took a long time to understand that I had a lack of isolation on one of the transformer that looped through the ground.
I changed both transfo and it still works perfectly for years
I had an interesting experience qlqs years ago with a dual mono amp.
two switches, two transformer, two pcb, two for cinch etc etc etc.
the amp worked perfectly if I operated one side at a time or if I plugged two different sources on each of the inputs.
but if I plugged a single stereo source on each of the two channels, a track between the two volume potentiometers went up in smoke and the fuses were blowing.
I took a long time to understand that I had a lack of isolation on one of the transformer that looped through the ground.
I changed both transfo and it still works perfectly for years
My nap clone has actually 4 separate secondary windings, you wont notice this on pics...
They are center-tapped and then paralleled by me to get only 1 center-tap conf.
238V AC on mains = +/- 35V DC on nap rails.
7.2OHM LOAD on both channels takes rails to +/- 28V DC...
If you ask toroidy politely, they will wind you whatever specs you need
They are center-tapped and then paralleled by me to get only 1 center-tap conf.
238V AC on mains = +/- 35V DC on nap rails.
7.2OHM LOAD on both channels takes rails to +/- 28V DC...
If you ask toroidy politely, they will wind you whatever specs you need
So you could have a dual mono build of this type if you chose to
The total test load current seems too much for the power supply though 
20% regulation is cruel or its an E-I type transformer.
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Yes my NAP200 clone transformer also has the same config as rensli. It has 4x28V outputs so 2 of the wires were combined to make a centre tap for each channel. It came with a diagram so it was quite easy to pick the correct ones.
My transformer came off the auction site, and seeing how popular the kit is there were quite a few sellers from China, HK, Taiwan that makes them. But the quality compared to toroidy, nuvotem, or hammond is anyone's guess.
My transformer came off the auction site, and seeing how popular the kit is there were quite a few sellers from China, HK, Taiwan that makes them. But the quality compared to toroidy, nuvotem, or hammond is anyone's guess.
This question was probably made somewhere, but does anyone know what did change in the Naim NAP 250 DR?
They mention the reference in the supply regulator, which apparently was a diode and now it's a chip. They also changed the transistor insulators, from mica to ceramic.
Those are all changes that could be used on the eBay DIY version probably.
Not wishing to sound disrespectful to the NAP 140 and NAP 250 following, has someone tried using NPN and PNP transistors at the output?
They mention the reference in the supply regulator, which apparently was a diode and now it's a chip. They also changed the transistor insulators, from mica to ceramic.
Those are all changes that could be used on the eBay DIY version probably.
Not wishing to sound disrespectful to the NAP 140 and NAP 250 following, has someone tried using NPN and PNP transistors at the output?
Hi Carlmart
I can't say much about recent models but you are right in seeing some changes in components and hardware that are inevitable over 50 years. All NAP models up to about 2000, share essentially the same design and components. The regulation in NAP250 models is to allow the maximum safe power rating possible with some of the critical semis used. No other reason, as far as I know. It's understandable that many owners prefer the sound with regulation because it can reduce hum and line noise but there are others who prefer the richer, unregulated sound of NAP110, 140 or Nait models for example.
Naim's particular sound quality relies heavily on the type of VAS transistors. You'll find these are completely the wrong type by SOTA standards but they've never changed throughout the NAP range over decades. Changing from a quasi-complementary to complementary design would also alter the distortion profile and sound quality quite a lot. It may even sound better to a lot of people but the point of building one of these clones is either that you just want a cheap, simple amplifier kit or you specifically want to hear the original, identifiable Naim sound character - that pace, rhythm, timing (engagement) thing. It's a pity that just building a cheap Ebay type kit with generic parts won't do that but then, you don't get million dollar sound for $10 anywhere.
I think a lot of experienced amateurs and professionals have tried to adapt and modify the successful Naim concept by trying their ideas in that format too. It's not a design by an engineer, though. It obviously started that way but was then modified by a talented and astute amateur. Thus the mods and tweaks apply only to the use of some specific semis and topology used in the prototype. Technically speaking, NAP models have nowhere to go, other than to lose that sound quality and move on in other directions.
We been rediscovering that here, with members sharing their experimental mods. To me, it just means taking any kit of choice and ensuring that the producer didn't omit half the important circuit features and the semis are original types or exact replacements for critical roles. The quasi-complementary topology of the output stage also contributes a large part of the sound quality but the actual NPN output transistor type has been changed many times over the product lifetime from switching type to LAPT and high linearity types, without drama.
For interest, some 250DR facts and figures here: PressReader.com - Connecting People Through News
I can't say much about recent models but you are right in seeing some changes in components and hardware that are inevitable over 50 years. All NAP models up to about 2000, share essentially the same design and components. The regulation in NAP250 models is to allow the maximum safe power rating possible with some of the critical semis used. No other reason, as far as I know. It's understandable that many owners prefer the sound with regulation because it can reduce hum and line noise but there are others who prefer the richer, unregulated sound of NAP110, 140 or Nait models for example.
Naim's particular sound quality relies heavily on the type of VAS transistors. You'll find these are completely the wrong type by SOTA standards but they've never changed throughout the NAP range over decades. Changing from a quasi-complementary to complementary design would also alter the distortion profile and sound quality quite a lot. It may even sound better to a lot of people but the point of building one of these clones is either that you just want a cheap, simple amplifier kit or you specifically want to hear the original, identifiable Naim sound character - that pace, rhythm, timing (engagement) thing. It's a pity that just building a cheap Ebay type kit with generic parts won't do that but then, you don't get million dollar sound for $10 anywhere.
I think a lot of experienced amateurs and professionals have tried to adapt and modify the successful Naim concept by trying their ideas in that format too. It's not a design by an engineer, though. It obviously started that way but was then modified by a talented and astute amateur. Thus the mods and tweaks apply only to the use of some specific semis and topology used in the prototype. Technically speaking, NAP models have nowhere to go, other than to lose that sound quality and move on in other directions.
We been rediscovering that here, with members sharing their experimental mods. To me, it just means taking any kit of choice and ensuring that the producer didn't omit half the important circuit features and the semis are original types or exact replacements for critical roles. The quasi-complementary topology of the output stage also contributes a large part of the sound quality but the actual NPN output transistor type has been changed many times over the product lifetime from switching type to LAPT and high linearity types, without drama.
For interest, some 250DR facts and figures here: PressReader.com - Connecting People Through News
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Well, as I am not aware of the major generations, perhaps a summary can be made by each generation supporter.
Putting the different schematics one after the other might be a way to do so.
I know two, but I get confused between the NAP140 and the NAP250.
i dont know .
Ian should know or Nigel Pearson
for info, I had this kit (nap 140) assembled at home for 9 or 10 years dormant.
I had assembled, listened and then demounted I found it very average.
Then I had the opportunity to repair genuine naim (olive and chrome bumper) and looking for information I came across this thread, I learned a lot, I applied the wise advice, sought the right compasants and I now have one of the best amp I've had in my life and yet I had a lot, really a lot, I have about 10 pairs of speakers and it is naim with all.
it's not the best amp in the world, but it's always a pleasure to listen to music with it.
Ian should know or Nigel Pearson
for info, I had this kit (nap 140) assembled at home for 9 or 10 years dormant.
I had assembled, listened and then demounted I found it very average.
Then I had the opportunity to repair genuine naim (olive and chrome bumper) and looking for information I came across this thread, I learned a lot, I applied the wise advice, sought the right compasants and I now have one of the best amp I've had in my life and yet I had a lot, really a lot, I have about 10 pairs of speakers and it is naim with all.
it's not the best amp in the world, but it's always a pleasure to listen to music with it.