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Old 30th April 2012, 02:11 PM   #891
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Default VAS re

[IMG]Click the image to open in full size.[/IMG]

To be strict a slight tweak of the resistor also ( 5K6 ) if sticking with the original intention of the circuit . If using a different transformer just ask . The boxed resistor is ( 50 / 40 ) x 4K7 = 5K875 to a good approximation .
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Old 30th April 2012, 07:18 PM   #892
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Quote:
Originally Posted by nigel pearson View Post
Hi , I was just going to switch off for the day . The idea is to have any ripple in the 50 V supply well above the smooth supply . It is cheap to do .

There will be very complex ripple free PSU designs you could try . However consider how bad the usual arrangement is . Anything will be heaven by comparison . This simple idea is fast and quiet .

The amp will seem more powerful because it will maintain full 38.3 V . If you lift the zener on a red LED you can even have 40V .

Let me know if you do it and the sound .

Nigel
Thanks understood. I like this solution of decoupling.
I need only trim my beautiful gold plated red pcb
next weeks I hope to begin assembling some parts.
talk to you soon
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Old 30th April 2012, 07:35 PM   #893
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Default Andrew

Just got me before turning off the computer . Thank Andrew for the nice correction . Will you be the first in the world to have a NAP 210 ( sort of between a 160 and 250 ) ? If anyone wonders I am off work sick and need to do this .
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Old 1st May 2012, 01:55 PM   #894
GEirin is offline GEirin  Argentina
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Hi Nigel
I have read your posts in this discussion. Very interesting. I was surprised by his revelation, the secrets of Naim, the 22K resistor at the collector of the input differential pair. Thank you very much.
Now I wonder: Are there other secrets in the Naim?. In the post, 98, 99,100 is argued that there is a configuration error. The connection point between the positive output transistor and the resistance of 27R is incorrectly represented in the diagram. What is your opinion?
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Old 1st May 2012, 02:07 PM   #895
GEirin is offline GEirin  Argentina
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Default R+C//R

Nigel, what is the function of R+C // R in the driver input?
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Old 1st May 2012, 02:09 PM   #896
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Phase lead/lag networks ?
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Old 1st May 2012, 02:38 PM   #897
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Hi , I read your post and thought you were absolutely correct . If I send you the amplifier that possibly inspired the Naim ( Sinclair Z 30 which was a kit in 1969 ) you will see that the Naim is much better and almost modern . The Sinclair Neoteric which preceded it is a work of genius however not commercial ( it is said to be a design classic and might have inspired the Lecson ) . If you get it right I hope you will post the results .

If you use the design in Self you will have to recalculate as he gives examples for Darlingtons or CFbP ( Szikai ) . I don't remember for a Quasi complimentary design although I might be wrong ? The Naim is half Darlington and half Szikai . I would guess choose a resistor half way between his examples perhaps ? You will have to follow all of his advice if you want to benefit ( mount the Vbe multiplier transistor near the power transistor as he shows ) . I found the Sinclair stuff so here is for anyone who likes tech talk .

very first "blameless" amplifier prior 1969

The advantage of doing it as you suggest is to make the initial switch on period better . After half an hour not much difference . To be honest Naim type amps do not draw much power and should be left to stay warm . I remember a man saying he would leave his girlfriend because she switched off his Naim amp . That will take a week to be right he said . I would say the Self circuit will account for fluctuations of power and room temperature better . If you do it please do a before and after bias check ( measure V of emitter resistors ) .I would like the before and after data for all to see if you can ( clip type test leads and over hours of use ) . Take readings when not playing music .

I have a name for the Naim . It is corrupted Blameless principle ( 22K ) . I approve of the corrupted part . Musically it is more correct .

If anyone wants to help me I am doing a project on the evolution of the blameless amplifier ( my private mailbox ) . I am saying the Naim is the first I know of which is in the pattern . Heath AA 1640 perhaps . Gogny 1964 is a starting point . Any you find will be interesting . All will have LTP input .

I should say this is a Thread about building NAP 140 Clone . Hope new people will ( you should ) .
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Old 1st May 2012, 03:50 PM   #898
GEirin is offline GEirin  Argentina
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Hi Nigel
If your intention is to improve the NAP (Naim), you could open another thread? "Improving the NAP"?
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Old 1st May 2012, 04:51 PM   #899
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Default Improving the Naim

First . If we are honest these are Naim inspired circuits . Julian Vereker told me no one can copy a Naim because the transformer design is special and other details . That is a bit like saying the AC Cobra car kits are nothing like an AC Cobra . Yes and no . However they are paying tribute to the design in both cases . If anyone reading this will never be a kit builder just go buy a secondhand Naim , it will almost certainly prove to be reliable . It will be an investment and will not loose money . That must tell you something ?

If you want to start a new thread invite me and I will come along . Call it the corrupted blameless amplifier or something . We can say we use ready made Naim clone PCB's as it saves investing in bespoke PCB's . We love Naim and it inspired a quest to make our own version . If no one comes to the thread we can invent another title until they do .

One thing will be to take out all of the compensation and protection and be responsible people and not party with the amps . You will be surprised how much we can take out and it will get better . I beg that you keep a clone to reference too . It is too easy to say a thing is better just because it's your own design . R/C question . I will answer that tomorrow if can . My next work project has turned up so I must get on with that .
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Old 2nd May 2012, 09:00 AM   #900
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Default R+C//R

There are plenty of text books that deal with the R+C//R compensation . Most require high level maths . I speculate that this was to get an amp without an output choke to drive Quad ELS 57 the reference speaker of Naim Audio 1971 . The Quad is a complex load . If anyone can find a Spice model for the Quads it might be fun to verify this . The striking thing is the R+C//R is not symmetrical ( nor is the output stage ) . This all looks like the work of a genius . Leave well alone I would say if asking . At the pub my friend suggested that these would have been set with a dummy load and square waves at ( 7 kHz I thought ) . In the Self type amp this would be a 100 R resistor .
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