NAP-140 Clone Amp Kit on Ebay

[Ruwe]

Originally Posted by GEirin

Nigel, what is the function of R+C // R in the driver input?

GEirin,
I'm away, but the discussion is getting so interesting... I can't resist... Now we are trying to unmystify the Naim's circuit secrets

Here are my 2 cents: The R/C circuits are adding some phase margin at frequencies starting somewhere above 700kHz if I remember correctly. I guess for improved stability. Unfortunately, the critical frequency of the R/C is determined by the drivers bandwidth; actually, by all transistors BW and poles that they create. For our DIY versions we don't know whether those R/Cs are optimal in any given semiconductor choice, but they work ... obviously.

I tried once to make them identical, because I thought "why not, why should they be different?". Well, I noticed that some imbalance was present. There is certain current flowing through them and when they are the "Naim way" the voltage drop across them is equal. If you make them identical, the voltage drop is different and that in my opinion will make the feedback to work harder in order to keep the output to 0V.

The question is why the current through them is different? I don't see it. Someone, please explain the Kirchhoff law to me ...
If Nigel or anyone else can give some idea that would be very nice. They are cleverly calculated for the same fc, but kind of adopted for different currents through them (I'm talking DC currents here).
The R/C groups and the 22k resistor are the 2 things that make this circuit different from the basic and not upgraded Self Blameless. I suspect that they are the reason for the good Naim sound plus, for some unclear reason, the quasi-complementary output. Would be nice to know scientifically how to tweak any similar circuit and to achieve the same excellent results.

[nigel pearson]

Ruwe it's two things . The Quad ESL 57's is the key and the imbalance between a Darlington and a Szikai pair also ( Apologies to the people who just love music , it is a fascination for people like me who should go to bed at 1.1 3 AM to talk about this ) .

It was a marriage . The sound between Naim and 57's is something to dream to own .

Adjust the power amp to +/- 27 V regulated for optimum ESL 57 performance .

[nigel pearson]

Kirchhoff is badly said by me to be

"The sum of the currents entering a node is equal to the sum of the current exiting it ". I have in fact combined two laws . I was taught that in electronics in 1974 when as usual I asked an audio question .

What does it mean ? It is like saying how many motors cars enter a roundabout ( road junction ) and how many leave . It should always be equal .

The implication of this is that everything is in the signal path .

When Kirchhoff can not be used one applies Gaussian Sphere principle . An op amp is like that . We can not enter the op amp so we say what is around the op amp is the Kirchhoff solution .

Apologies to kit builders and music lovers .

Kirchhoff is obvious . Yet it seems to escape the attention of many audio engineers .

KIrchoff - Bunsen Burner . We all used them at school .

[nigel pearson]

[IMG][/IMG]

There seems to be no decent Gauss explanation on the net so this is how I learnt it .

See the simple object inside the circle . That's the op amp and we then say it is a node .

[masood]

Originally Posted by filholder

Current stage, progressed slowed a great deal my deadly man flu

dear sir ,
plz send me its pcb diagram.thans

[Ian Finch]

Masood, This is a thread about kits bought on Ebay. The post by filholder is four years ago.
If you want to copy Ebay kits you can read any Ebay trader's site quoted from the posts in this thread and maybe you can see the images well enough to copy.

As you can buy the complete kit for the parts cost, it may just be a waste of materials. copying them.

[masood]

dear ian,
thanks alot.yours masood

[nigel pearson]

A freind of mine originated this circuit as far as I know . He isn't mentioned here . Keep a copy of this safe if you ever want to do a tube design . It also shows how a LM317 can be used at higher voltages . This is a very good design .

DIY Test Equipment for Audio and Ham Radio Enthusiasts

[luisitoloco22]

Hello everyone: I wanted to consult those who have created this circuit if used a voltage exceeding 40 volts feeding symmetric, for example: 45 volts symmetric
regards

[ciariello]

Originally Posted by ciariello

i attach some picture ...
maybe could be useful to find the problem...

hi guys i have a question. My Homemade NAP140 has a problem assembled in 2010.
The resistors R6-R7 (on both channel) are blackened, browned and very hot when you touch them. I state that the amp works but I think it's a symptom of some problem.
Can someone help me?