Intermodulation distortion is a fancy term for signals affecting one another. If an amplifier were perfectly linear, then one signal would add to another perfectly. In practice, an amplifier is not perfectly linear and this causes the signals to interfere with one another and this causes distortion. This rather unnatural, electrical distortion mechanism (air doesn't suffer this) makes it harder for our brains to discriminate the original signals.
Ok traberbam ty but i don't know how we can hear that on a youtube video done with a smartphone
Someone try this KIT of 250.2 ?
http://bbs.hifidiy.net/thread-1346141-1-1.html
He copy the PCB directly but seems to have a mistake on negative power rail
And he draw schematics of the 250.2 but i don't find someone who can confirm it works proprely
Someone try this KIT of 250.2 ?
http://bbs.hifidiy.net/thread-1346141-1-1.html
He copy the PCB directly but seems to have a mistake on negative power rail
And he draw schematics of the 250.2 but i don't find someone who can confirm it works proprely
Good day
I buy this board in Ali store about 5 month ago but that PCBs have of few mistakes (not enough roads) I mail to trader and he say “you need solder with wire of all not enough roads…” hhhhhh
This PCBs stay with me and I not make it to full amp )
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Good day Cris
Yes correct
In attachment Ali NAP250.2 PCBs with one of mistakes
)p.s.
Dear Chinese boys if your watching this post please correct yours mushkelya boards !!!
)) h h h h hAttachments
Original NAP models have been altered many times, beginning with the first range in the 1970s, as you would expect when newer and better audio semis were still being developed. If your schematic is of that same official Naim NAP 250 amplifier module that has been floating around the internet for many years and among repairers and hobbyists for even longer, it will be quite different to anything Naim have produced in the last 20 years or so. The current DR versions of NAP250, 300 and 350 would probably indicate how far their power supplies have come since early days.
l would not assume anything about that early schematic being useful for later versions of NAP250 nor is there any correlation with Avondale Audio basing their clone on it and fitting slug transistors like MJ15003, as output power transistors. That's more or less sticking with the past for its own sake or because they are cheap and available everywhere, rather than taking advantage of what's improved in recent years.
l would not assume anything about that early schematic being useful for later versions of NAP250 nor is there any correlation with Avondale Audio basing their clone on it and fitting slug transistors like MJ15003, as output power transistors. That's more or less sticking with the past for its own sake or because they are cheap and available everywhere, rather than taking advantage of what's improved in recent years.
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Yes ian I agree that we are working here on an old diagram, some transistor references are no longer available whether it is the ZTX108/384 or those of the output. So I had thought that working from the 250.2 diagrams could make it possible to have the right transistor references, it is still necessary to have reliable diagrams which I doubt about those that I have just found...
Someone said on this forum (Jp43?) that putting the ZTX384 instead of the 2N5551 improved the sound, so I thought why not give it a try, there are models on eBay that seem to be, given the photos of the old ones (so can be real and not counterfeits)
I'm pretty sure about my schematic and PCB on the old 250, so redoing better routing, modifying the output transistors, with transistor pairing and if I find real ZTX384/108s, the result should already be improved.
PS: I just saw that Dorkmeister who made his 250 clone from my PCBs and my component list posted on this forum and seems to find the result very good, after I don't know what point comparison he has in terms of amplification since he did not know the naim amps.
PS2:If I think that the transistors have a great importance in the final result, I think that all the components have their importance, I chose only high quality components, resistors at 0.5Watts in order to reduce noise, Capacitors are all MKP or organic polymer (except the unavailable 39pf which are MICA), I think this plays into the end result.
Someone said on this forum (Jp43?) that putting the ZTX384 instead of the 2N5551 improved the sound, so I thought why not give it a try, there are models on eBay that seem to be, given the photos of the old ones (so can be real and not counterfeits)
I'm pretty sure about my schematic and PCB on the old 250, so redoing better routing, modifying the output transistors, with transistor pairing and if I find real ZTX384/108s, the result should already be improved.
PS: I just saw that Dorkmeister who made his 250 clone from my PCBs and my component list posted on this forum and seems to find the result very good, after I don't know what point comparison he has in terms of amplification since he did not know the naim amps.
PS2:If I think that the transistors have a great importance in the final result, I think that all the components have their importance, I chose only high quality components, resistors at 0.5Watts in order to reduce noise, Capacitors are all MKP or organic polymer (except the unavailable 39pf which are MICA), I think this plays into the end result.
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I can't say it's actually the case here but when transistor types are simply swapped for others because they should, in theory, work fine and are cheaply available to kit suppliers in China, there will almost certainly be some other changes necessary to maintain operating conditions in line with the original product. For example, you may have wondered like I did, why Naim always stuck to those tough little Zetex/Diodes Inc. VAS transistors such as ZTX653/753. Well, if you swap them for any "correct type" low capacitance VAS transistor there, it's "poof"- gone is the Naim PR&T sound effect. 'interesting how some errors can lead to better or rather, more entertaining sound quality, don't you think?
I doubt if any other engineer/designer would think and work like JV today, but his self-taught design and manufacturing ideas are what we we face when messing with DIY Naim clones and trying to reconcile the differences to what we know today, with the benefit of up to 50 years hindsight.
Components are an issue but not to the degree that semis are. I don't recall any mica types specified in Naim products though and any benefit might only be stability at RF frequencies which is somewhat out of our reach. Generally speaking, don't substitute them just because they are old, different and thus "cool."
I doubt if any other engineer/designer would think and work like JV today, but his self-taught design and manufacturing ideas are what we we face when messing with DIY Naim clones and trying to reconcile the differences to what we know today, with the benefit of up to 50 years hindsight.
Components are an issue but not to the degree that semis are. I don't recall any mica types specified in Naim products though and any benefit might only be stability at RF frequencies which is somewhat out of our reach. Generally speaking, don't substitute them just because they are old, different and thus "cool."
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I've also changed 2N5551 with ZTX108/ZTX384 (I've got both). I'm using wima FKP caps; I assumed better than MKP.
My bias was changing with temprature. I seperated the power transistors cooler in the box. Now, there is a wall between pcb&cooler. This is better.
Film caps are really only a problem because of size. Polypropylene (MKP) is bulky and this can cause more problems than the type of plastic film. They can be moved about to reduce interference and hum to some degree but often, what you really needed was just a tiny COG/NPO type ceramic cap. Consider the requirements and location first - the appropriate type of cap then follows.
Audio design is tricky for many reasons. For example, sonic perception is not directly measurable by instrumentation. It’s also tricky because system behaviour is more important than individual component behaviour. This is hard to get your head around.
Perhaps counter-intuitive, is the possibility of designing a better system by using “worse” components!
We first consider the components because that’s a lot easier. They have data sheets with simplified parameters. A transistor with higher ft must be better, right? Or a new power transistor must be better than an 40 year old one. Well, yes but what is better as a component is not always better in a particular system.
This is why there is confusion and argument about Naim component choices and upgrades. Substituting a better part can actually make things sound worse, even though it doesn’t seem to make any sense.
Perhaps counter-intuitive, is the possibility of designing a better system by using “worse” components!
We first consider the components because that’s a lot easier. They have data sheets with simplified parameters. A transistor with higher ft must be better, right? Or a new power transistor must be better than an 40 year old one. Well, yes but what is better as a component is not always better in a particular system.
This is why there is confusion and argument about Naim component choices and upgrades. Substituting a better part can actually make things sound worse, even though it doesn’t seem to make any sense.
Mica dielectric goes back a long, long way to radios where stable capacitance was critical to tuning. Stable meaning very low drift vs temperature and time.
In audio, on the other hand, the instantaneous dielectric properties are critical, unlike in radios.
There is a paper about a study of dielectric properties and their pertinence to audio circuits. It has been linked many times here but I don’t have it handy.
I did my own listening tests with mica and ruled them out.
In audio, on the other hand, the instantaneous dielectric properties are critical, unlike in radios.
There is a paper about a study of dielectric properties and their pertinence to audio circuits. It has been linked many times here but I don’t have it handy.
I did my own listening tests with mica and ruled them out.
'Only just noticed that comprehensive article above - very good and helpful content .
I'm sure there are still some valid applications for mica caps in audio systems but I think mica's resurgence in popularity follows the antiquity as much as any fine sound quality it's said to confer, particularly for tube amplifier designs. Improved sound quality usually implies increased or modified types of distortion. The attraction though is much like the audiophile reverence for oil filled paper caps and essentially, anything old and dodgy from the tubes era, when popular audio was delivered universally by "steam wireless" and Bakelite disc recordings.
If you really do need stablity for some reason, such as making a low drift oscillator, silvered mica can solve a few problems there, if the price is competitive and values higher than a few hundred pF capacitance are still available. These types have contacts formed by sputtering or vapour depositing a thin layer of silver metal directly onto the mica sheet surfaces, forming contacts with better stability than the simple plated steel or brass clips used in standard mica caps.
I'm sure there are still some valid applications for mica caps in audio systems but I think mica's resurgence in popularity follows the antiquity as much as any fine sound quality it's said to confer, particularly for tube amplifier designs. Improved sound quality usually implies increased or modified types of distortion. The attraction though is much like the audiophile reverence for oil filled paper caps and essentially, anything old and dodgy from the tubes era, when popular audio was delivered universally by "steam wireless" and Bakelite disc recordings.
If you really do need stablity for some reason, such as making a low drift oscillator, silvered mica can solve a few problems there, if the price is competitive and values higher than a few hundred pF capacitance are still available. These types have contacts formed by sputtering or vapour depositing a thin layer of silver metal directly onto the mica sheet surfaces, forming contacts with better stability than the simple plated steel or brass clips used in standard mica caps.
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Note: I haven't seen mica caps that contain actual silver. They have normal metal deposited on to the mica surface; it's just that the process of doing this is called "silvering". This term sometimes gets lazily truncated to "silver mica".
I do worry a little that some folks might erroneously think that "silver mica" has superior audio qualities because it contains silver!
That's why I always call them silvered mica or just mica.
Seramic high voltage caps are nowadays (W-Jung.pdf is very old article) very stable (this knowledge somewhere in this forum). For example for class 1 seramic caps are written as "These ceramic capacitors offer a high level of stability and exhibit low loss levels and they are ideal for use in resonant circuits." https://www.electronics-notes.com/a.../ceramic-dielectric-types-c0g-x7r-z5u-y5v.php.
Yes, most forum heavyweights have generally supported the use of NPO (leaded format) or COG (SMD format) ceramic types in audio circuits, often including the feedback loop, for many years now. Of course, they are limited to small (pF) values in practice. Cheaper, smaller standard ceramics types are definitely still no-nos though, unless simply mains or power supply bypassing caps or similar.
I've seen this done and even done some metallizing and electroplating of plastics, ceramics, carbon-graphite and timber myself. I was using copper, silver and a range of special alloy wires containing nickeI, that unfortunately, weren't identifiable from available documents.
I worked 10 years as tech support for a multinational component and industrial electrical parts manufacturer, so I learnt a few things about old-time manufacturing techniques from their library of well-worn, heavily bound manuals for making Stackpole process carbon comp. resistors, pots and other common components of radios, TVs, audio and communications equipment . Their quality control systems were a maze of logical loops and traps - no doubt, the work of boffins of the day.
It's interesting that carbon comp. resistors live on in these tube revival days. Allen Bradley and Ohmite in the US, still supply them (at a price!) for military applications, where their ability to withstand high energy pulses is essential. If you test these resistor types over some years in use though, you'll see why they were hastily shown the door when compact domestic colour TV and video systems arrived.