Bench Monitor Amplifier. Part 1. Based on Naim NAP250 clone kits. Giving 50 watts into 8 ohms.

[@sunnykfc]

I think this is the clone of the nap250 in 1970's, do you know of any clone of the recent DR version?

[@MichaelBeeny]

Yes, it is a 250 clone. I've never really liked the sound of NAP250 or other amps based on this circuit. Too slow for my taste!

[@sunnykfc]

@MichaelBeeny thanks sir.😊

[@dab9742]

Hi Beeny, Have you tried the MJ15024G / MJ15025G 2x15W 8Ω Class A Bipolar Amplifier based on the 1969 JL Hood Class A? Kit sold by Audiophonic, it works very well, is very pleasant to listen to, very easy to set up !

[@MichaelBeeny]

I'm not a lover of class A. I don't see the point of it. If you operate most amplifiers in class AB you have the best of both class A and class B If you bias a class AB correctly, you will have no crossover distortion. So, what do you gain? Nothing except lots of waisted power consumption, lots of heat. So why would you do it?? It will not sound better and certainly does not measure any better. Still, some people dream it sounds better. Some people believe in fairy's and gods!!

[@dab9742]

@@MichaelBeeny It is only 2x15 watts, not overly hot (37-39°) and I assure you it works very well. The advantage is that it gets to the right operating temperature more quickly, it's immediately ready to go, but in my humble opinion, it should only be used for speakers with relatively high output.

[@MichaelBeeny]

@@dab9742 I'm sure your right. No reason for it not to sound good. But it won't sound better than class AB.

[@MarcelOoms]

Hi Michael, nice projects and gear! I like the simple look of the case. Where did you get it?

[@MichaelBeeny]

Hi Marcel, good to see you here again. I've had the box a while now but this was the product from eBay JC229A Full Aluminum Amplifier Case Preamp Chassis DAC Box PSU Enclosure New. Quite a few to choose from, some with sinks, some without. Postage is the killer, silly money!

[@Yradex]

Hello Michael! Great project and presentation. One question - where do you connect output to the speakers. I can see positive out on the PCB but where is negative? Thank you and keep up good work!

[@MichaelBeeny]

It goes to the 0 volts on the power supply board.

[@ford1546]

@@MichaelBeeny What are we going to do with the nap250 clone when it is so bad. Even an old one Superscope by Marantz R-1240. from the 70's has better sound quality and you can easily hear it by comparison. much better to buy L12.2 L15 L20

[@MichaelBeeny]

@@ford1546 I only use it as a monitor with my small Wharfedale speakers on my Video editing PC. It's not demanding work ands it's fine for that application.

[@Unker_Spunkanathan]

Hi Michael, let us know how the amp sounds when you transformer arrives. I was deciding the LJM nap250 vs MX50SE and eventually bought the MX50SE coz everyone seemed to have only good things to say about it. Perhaps it's coz the NAP250 has some expectation to live up to since it was inspired by the Naim. Also interesting that you did not use a buffer or preamp for this project. Space constraint?

[@MichaelBeeny]

Until I have made full tests I don't know the input sensitivity yet. As it will be fed 90% of the time with the PC, probably wont need a pre amp. We shall see!

[@rtonge3753]

Hi Michael, thinking of buying this set up and getting my soldering iron out. I see on the power board you have a blue wire that goes to the positive speaker terminal, what about the negative terminal? This must be pulled from somewhere else please can you help. Thanks Rick

[@MichaelBeeny]

Good question Rick, it goes to the 0volts on the power supply board. Or via the speaker protection boards speaker negative. Don't forget to use such a board as the amplifier needs a few seconds delay before the speakers are connected. I cover this in the video, or the follow up if I recall.

[@rtonge3753]

@@MichaelBeeny brilliant thanks

[@moodyga40]

no amp should put dc on the output when turned on. dif drive may not be working

[@ford1546]

@Cheerful YC Michael can you say your opinion on NAP250 CLONE? On ebay it says that I shall adjust power to transistors in the following way. voltage across the cement resistor = 1.5 MV-3MV. I have adjusted to approx. 116mv according to the measuring instrument I have. Otherwise the heat sink will not get any temperature above room temperature when it is only on without sound input. This is MUCH more than recommended. Will this affect the sound quality? Heatsink does not get so hot after 30 minutes! about. 30 degrees in a room of 33 degrees

[@Unker_Spunkanathan]

@skrotkalle skrotkalle, I just acquired a Chinese clone of the nap140 and that's why I am revisiting this video. I understand that there are only slight difference in the design of the different version of NAP. Main changes were in the implementation of the power supply. From the Internet, I gathered that the rail current (QI?) should be around 36~38mA, not more than 40mA. The current through the output transistor would be around 15~20mA. I set mine around 👆🏻 and the amp is just about warm to touch, perhaps 40°C.

[@ford1546]

@@Unker_Spunkanathan @Cheerful YC I understand. What are we going to do with the nap250 clone when it is so bad. Even an old one Superscope by Marantz R-1240. from the 70's has better sound quality and you can easily hear it by comparison. much better to buy L12.2 L15 L20

[@ford1546]

@@Unker_Spunkanathan nap 250 also uses a 10uf tantalum capacitor which is not the best capacitor type to use at the audio input on amplifiers. what happens to the sound quality and brighter areas if you remove it or replace it with a good quality capacitor??

[@ford1546]

@@Unker_Spunkanathan @@Unker_Spunkanathan Why so many small transistors? have amplifiers built-in EQ.? An EQ. is only transistor and capacitor and resistor!

[@Unker_Spunkanathan]

@@ford1546 really have no idea about the different transistor stages. Don't know enough for electronic design. My 1990s harman kardon had even more parts on its pcb

[@pedropaulofontes4084]

You thing Nain250 best amplifier or LA12? What do you prefe?

[@MichaelBeeny]

It's like chalk and cheese, no comparison at all. The L12/2 wins by a VERY LARGE margin.

[@edwardbalboa5528]

The genuine NAIM amps ARE bandlimited + use very low bias..... Don't understand your complaints , as the board is an accurate clone of naim

[@MichaelBeeny]

Low bias means crossover distension, that I don't like. You cannot have no crossover and low bias, that's called class B. Why would you reduce the band flatness within the range of hearing? Should be VERY flat from 20Hz to 20Khz . This amplifier has a dropping HF and visible cross over as supplied. That is not the kind of results I expect from a good amplifier. Both can be fixed, as shown in follow up videos.

[@moodyga40]

25 x 1.414 = 35.35 v /0/35.35 v 70.70 volt swint it will work good

[@MichaelBeeny]

Don't forget the voltage drop across the diodes!! Welcome Ian.

[@moodyga40]

Yep .6 volt x 4

[@ford1546]

NAIM NAP250 CLONE I made a bigger comparison between NAP250 CLONE and 5 standard mid-range amplifiers from the 70's and 80's and 90's. I was disappointed with the sound quality of the NAP250 CLONE. It has such a dark sound. even superscope r-1270 from 70's has better and clearer sound. almost all old amplifiers i compared to had better sound quality than the nap250 CLONE has. understand well why you do not like the sound of naim amplifiers

[@cheerfulyc7125]

Frankly, there are a lot of different versions of the NAP design in the clone market ... I got the impression that you are using not the 100% clone version. I strongly recommend you to try out the version using the Sanken 2SC2922 as the output transistor. The board is a direct clone of the NAP 200 even in its circuit board layout! Good Luck!!!

[@ford1546]

@@cheerfulyc7125 I have (sanken 2sc2922) edition. (L12.2) (L15) (L20) are better amplifiers with better sound! Naim nap250 is a bit dark and has a bad treble! the person in the video the person in the video has said that he has sold Naim in store before but has never liked the sound out of Naim amplifiers. I was very disappointed with the nap250.

[@cheerfulyc7125]

@@ford1546 Yes, NAP250 never sounds as good as the NAP200! Also, in the clone market, many have found the clones don't sound as good as the original, even if some are using a direct clone copy (despite using the exact component values) can attribute to the following issues ... (1) The transistors especially in the differential stage are not closely matched (The Chinese will not give u direct match pair for that kind of money one paid) (2) The input gain stage is not directly thermal coupled ... causing thermal gain drift (3) If one deploy a fully regulated PSU in the clone, the sound can even be better than the original! The NAP200 is simply a gem if one know what one is doing!!! 🙏🙏🙏

[@ford1546]

@@cheerfulyc7125 nap 250 clone uses a 10uf tantalum capacitor in series on line inn. sound in. Tantalum is not a good capacitor for this use.

[@cheerfulyc7125]

@@ford1546 Yap, this is one of the many factors that it is dark sounding! Also, in the real world, NAP250 is never better sounding than the NAP200, that is why Naim upgrade its product line from NAP250 to NAP250 DR using a completely new circuit topology and the output transistors are totally proprietary (known as NA009) which has better output current and transconductor abilities! The new NAP250 DR amp is now better sounding than the NAP200 and there is no way for the Chinese to clone it!!!

[@MichaelBeeny]

Click here for part 2 kzbin.info/www/bejne/rGHXn4mHqMSKipI