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Old 29th September 2012, 01:39 PM   #971
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by nigel pearson View Post
............I do feel that the Naim is a ..........case of bad is good ...............
I would re-phrase that into
Naim have very deliberately "tuned" the sound of their amplifier to appeal to a particular customer.

That "tuning" does not make the amplifier bad, nor does it make the amplifier "not good".. It is made to suit a particular purpose. Make money for Naim.

You listen, you like, you buy.

That is not a put down, that is pure business sense.

My first two posts made no mention of whether Naim were good or not good or bad.

They were simple statements and as such they did not deserve the abuse that Har posted !
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Old 29th September 2012, 01:50 PM   #972
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That's right . I think we can have our cake and eat it with this . It means trying each factor very gently to see ones own taste . What is depressing here is that the kits are not as Naim as they should be .

As someone who used Naim for years I always liked their way of making me enjoy music . Sometimes that was when feeling very jaded returning from work . The negatives completely disappeared when using Quad ESL 57's . Even heard that using the Nait Mk 1 . I have no explanation for that except Julian Vereker loved the Quads . Depth and neutrality were the missing qualities . CD and " better " amplifiers never recused me from being knackered, LP12 and Nait did .
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Old 29th September 2012, 07:50 PM   #973
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Hello

AndrewT or Nigel can you open a new thread about that all Hitachi Fet amplifier please.
I ask you guys because to me English a second language(ESL), I'm far from fluent English.
I'm interested on that amplifier a lot, also I would like to discus the replacement of the J Fets.
Since those Hithachi JFet no longer available probably we could use replace them with Toshiba 2SK170 or 2SK246 both has at home limited quantity.
The rest of Hitachi mosfets I have.
These amp circuit look simple, comes from a great source.
We can play also to replace the power Fet with bipolar if that would be better.
I did started a thread several years with a Darlington amplifier but I got so much negative from some guys I gave up the thread not the amplifier.
Al do I built the amp and very-very hard to explain how great that amp sound.
I built and tested so many amp (close to 100 different with fet, transistors, tube chip) but these amp stand out sound wise compare to Aleph30 clone, X, NCC200, Naim Clone, Symasym, ProFet etc
All my respect to the amplifiers I mentioned, they are not bad at all, actually many of them great amp!!!!
I didn't had not much success on the forum with that thread.
Again (one of)the best amplifier (if not the best) I ever heard in my system or I owned!!!
Also I had over 300-400 commercial amplifier over the last 22 years. Not to many $$$$ but still
nothing come close sound wise at all.
Sometimes I do repair amplifiers sometimes buy & sell them especially at the beginning when I was searching for a good sounding amp..
Some guys who hate Darlington started to post negative thinks there and killed the tread.
That is the reason why I would like someone would be so kind to open a new thread with these Hitachi schematic.
Thanks
Greetings Gabor
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Old 29th September 2012, 11:12 PM   #974
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I don't understand anyone criticizing another person in these threads . The exception is if something has safety problems . There is always someone who knows more , I often find those who know most show it by communicating better . I wonder if hi fi died because it became technical when in truth it is about liking music ? I have heard many products which have measurements that look so good as to be perfect . Often the sound is less than excellent . Often many years later the reason is found . Here is one . To this very day I have no idea why . I wonder if the speakers I liked at the time were not allowing it to shine ? It claimed zero distortion which was probably true at the time due to ability of measuring equipment to detect it . Radford said all distrotion below noise , no meaningful way to measure it .

A Paul Kemble web page - the Radford HD250 and ZD22 amplifiers.


Darlingtons are excellent devices and make designing easier . Complimentary feedback pairs ( CFP ) are better, they are slightly more prone to oscillation . A Darlington and CFP can be made from the same parts . Then there are output triples of which the Quasi Complimentary versions are especially interesting ( Quad 303 ) . The Naim is half Darlington and half CFP and is called Quasi Complimentary . MOSFET's on paper are the worst of all devices . I find in real life they are the most obliging .

Although this is not Naim talk it is helping us to understand Naim better . Naim selected Quasi Comp as the best compromise , many still believe this to be true . If I doubt it I feel the Quad triples in the 303 even better . Rumour has it NAP 160 was to be 303's replacement . The design was adapted to Naim needs . I have no idea if it is true . I suspect it is . It makes sense as the 405 came out at the same time more or less . The 303 continued and is probably a better amplifier than the 405 or early NAP 160 .
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Old 30th September 2012, 04:34 AM   #975
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[QUOTE=nigel pearson;3184202] MOSFET's on paper are the worst of all devices . I find in real life they are the most obliging .

Hello Nigel
I agree with these statement. I tested the ProFet (french) amplifier (clone) with Renesans mosfet and I didn't like the sound at all. Soft, muddy......(my fried like that set up a lot) So I changed the Renesans mosfets to Exicon (it has more transistor like sound). The sound opened up it was much cleaner and the bass got deeper has more controlled.
All do the same time I did replaced the 2PC 0.22uF capacitor on the PC board, the Wima MKP to Russian PIO.
What is interesting Jean Marc prefer the Hitachi mosfets at his commercial amp and what he listening at home to>>>>
Now I have a couple pair Exicon, orig Hitachi, and some Class D mosfet at home.
Can be the Renesans not the same quality than the Hitachi was, I don't know.

Which Naim clone do you have?? From Jim's Audio. I never heard that.
And what type of transistors you use.
All I can say I like my NCC clone very much but how I wrote before I spent a lot of time (weeks). I did listen almost every component..
Now I have some problem, it was built as a Stereo amp.
I used 4PC AeroM (Mallory) 66 000uF capacitor CRC set up PS.
Now I'll rebuild it I want to make it as a dual mono amp with two separate power supply.
I only has 4PC AeroM capacitor so that is not enough to build a CRC capacitor bank. And I don't have room enough for more large can capacitors.
I plan to use 4PC 18 000uF Panasonic and 2PC 10 000uF Nower (audio cap) for each channel.
I have to do more listening test with the new caps com pare to the AeroM. Also I want to test Greg B modification..
If the caps degrade the sound even a bit I have to give up my dual mono dream.
Each transformer 250VA and I get 40VDC.
I have a larger transformer 500VA but that would give 50VDC (bit to high). With that I can't use the AeroM caps. I need min 63V caps. I have some Nippon CC 100 000uF 75V but I don't know much about the sound quality.. I never tested.
I don't want to use regulated PS. Tend to sound thin and clinical. I used only the transistor type in my Hiraga Class A and the Monster H. All do both class A amplifier..
Probably mosfet fore regulated PS would be better who knows. A lot of test again..
I have 4PC 50 000uF Kendeil caps but I keep those to my Darlington amp.
Will see, all I know I like these amp sound better than many high power Class A amplifier and less heat and lower power bill..
I have 2PC NCC200 PC board clone, home brew not supper quality, if you want them you can have it free. Just to test the NCC type to.

Greetings Gabor

Last edited by gaborbela; 30th September 2012 at 04:39 AM.
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Old 30th September 2012, 08:56 AM   #976
AndrewT is offline AndrewT  Scotland
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I believe the first C in a CRC has much less influence on the Audio Sound that comes out of the amplifier.
The decoupling has the most influence in keeping the audio signal uncontaminated.
The last C of the CRC is possibly the next most important.

The first C is there attenuating interference. Use the best cap for that job and that job alone. Don't select on the basis of "good Audio" characteristics.

I think it was JCurl that suggested the first C (at the mains input) should be a 10uF polypropylene. That is obviously an extreme case of attenuating the interference at the earliest stage.
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Last edited by AndrewT; 30th September 2012 at 08:58 AM.
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Old 30th September 2012, 09:54 AM   #977
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Hi Gabor ,

I had any Naim amp I wanted at one time . I mostly used a Nait 1 with Royd speakers as compared with most things they were 90% as good as I needed . Even though I love classical music the slightly wrong sound I got was not so different when comparing live sound in slightly less good acoustics . I can live with that . Quad ESL 57's are the cure . The Royd has the attack as if Quads . The tonality is slightly wrong .

Then poverty struck . I had to improvise . I had to learn why I like what I do and build it . Unfortunately the building becomes interesting in it's own right . 80% of what I build is a waste of time , of which 90% looked a waste of time . How can one give opinions if never having tried ? Simulation is not trying , if does say perhaps that is a waste of time to try some things . 10% of what I build is better than expected . A small percentage looked totally wrong and wasn't .

I have a FM transmitter that costs $8 . It is one of the least wrong things I have . !

I was talking to Bob Stuart in the late 1970's . I criticized him for allowing Naim to beat him to the market with the Naim NAP 160 . The Meridian 101 103 ( 105 ) was Bob's Naim . Bob gave a lecture called something like " Distortion in amplifiers due to loss of information " . Bob argued that any device that could be eliminated will improve sound quality . Others say each transistor is like a photograph of a previous photograph . Without reference to the original photograph it looks great . The original had more detail . Obviously minimum standards of distortion and bandwidth need to be guaranteed . After the lecture Julian Vereker stayed behind and begged Bob to fast track him on amplifier design . Julian was a mechanical engineer and knew as much as the new-Be's here . Bob told Julian to buy a Sinclair kit , make it reliable and add the largest power supply he could . Bob laughed and said " I didn't expect him to go into production with that " . The truth is slightly more complicated . Julian met Alan Mornington West who gave Naim the intellectual gravitas they needed . However it was Julian who listened and rejected . It is this ability to reject seemingly good circuits which is the difference . In my experience many people who are capable of designing great amplifiers do not have the ability to know when they have failed . Somehow they let their best and most learned friend the oscilloscope listen for them . Or ask Mr LT Spice what he thinks .

Naim amplifiers sound badly wrong when mismatched to a system . I have no idea why . The marriage with the Quads suggests it is not the Naim that is to blame . I can say that marriage is so dramatic as to be like the lady who takes her glasses off and lets her hair down in an old film . She was always the nicest lady he knew , now she is beautiful .

Power supplies are fun and go on for ever as research . Try all the wrong things like 2 x 2200 uF . Just to say you have . At low levels they might sound better ! One could have PSU's with options .

The Hitachi might be best as usually used . It can be simplified further if doing a Bob Stuart . Here is a version very faithful to the original with very simple PCB layout . I can absolutely guarantee this layout as a good stating point . If anyone gets to make some PCB's I would like some .

87MOSFET
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Old 30th September 2012, 10:37 AM   #978
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Quote:
Originally Posted by AndrewT View Post
I believe the first C in a CRC has much less influence on the Audio Sound that comes out of the amplifier.
The decoupling has the most influence in keeping the audio signal uncontaminated.
The last C of the CRC is possibly the next most important.

The first C is there attenuating interference. Use the best cap for that job and that job alone. Don't select on the basis of "good Audio" characteristics.

I think it was J Curl that suggested the first C (at the mains input) should be a 10uF polypropylene. That is obviously an extreme case of attenuating the interference at the earliest stage.
Hi Andrew . The regs time constant is 5CR < 2 seconds for the discharge resistor . Douglas Self thinks that 470 nF is an optimum maximum .

I tried to stop Either-Net over the mains appearing in my amplifier . I had very little success . Naturally it is designed to penetrate through the house and overcome the filtering devices that even washing machines have . I tried classical Pi filters with both common mode and differential chokes . I would call it RF aids , it's that bad . I could not get an exact spec for how it works . That would help .

Anyone have any ideas ?

I am supposed to be installing new mains sockets today in the kitchen . Then designing something with a hex inverter . I am not doing well am I .
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Old 30th September 2012, 10:57 AM   #979
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by nigel pearson View Post
Hi Andrew . The regs time constant is 5CR < 2 seconds for the discharge resistor . Douglas Self thinks that 470 nF is an optimum maximum . .
I was replying to the query on PSU and the capacitances he had to work with to create two monoblocks from one stereo.
Quote:
I used 4PC AeroM (Mallory) 66 000uF capacitor CRC set up PS.
Now I'll rebuild it I want to make it as a dual mono amp with two separate power supply.
I can't see what your 470nF has to do with his capacitors.
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Old 30th September 2012, 11:26 AM   #980
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10 uF at mains input and John Curl , 470 nF was D Self's recommendation . Nice idea , needs a discharge resistor to meet regs . I have never been clear if a big 10 uF high voltage caps are allowed for this use ? One can use 5 x 2.2 uF class X2 which certainly are . As motors use these non X2 caps I suppose they must be OK ?
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