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Old 28th November 2012, 10:35 AM   #1001
Telstar is offline Telstar  Italy
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Quote:
Originally Posted by nigel pearson View Post
With some reluctance people had to accept Naim were right and they could justifiably state a feedback pair could perform exactly as an PNP or better . When PNP's caught up using all CfbP seems even better .
Hello Nigel,
Reading you is always a pleasure, and I'm sure nobody would object if you indulge more in British hifi history

I found that matching the drivers in a CFP is very critical, how about the Naim's quasi?
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"The total harmonic distortion is not a measure of the degree of distastefulness to the listener and it is recommended that its use should be discontinued." D. Masa, 1938
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Old 28th November 2012, 11:33 AM   #1002
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Hi Telstar ,

The whole thing about all conventional output stages is they seem less trouble than people would expect . This is because it is a current amplifier with a voltage gain of between 78% MOSFET and 97% CfbP . The 94% of Darlington's is especailly fortunate I have found for the more old fashioned designs ( Velleman sell one ) . The Naim is one side CfbP so it sort of answers the question . In recent times I have become very brave and wire my outputs away from the bias stage on long wires . No real problems . This means I don't have to ruin PCB's when trying new things . When building a CfbP I solder the transistors together so as to be one device . Why we can not buy a super transistor like this I do not know ? The stability can be enhanced by soldering a small capacitor between base and collector of the input device . This will mimic the slightly slower transistors of old , it will have superb linearity . Some people are noticing medium speed transistors sound best . It is probable that they have a better balance of gain , stability and bandwidth ?

About hearing . 200 Hz to 10 000 Hz is not bad ( a good TV ) . Some research shows 2 MHz has some relevance to our hearing ( waveform shape ) . I supplied some KEF T27 tweeters to Oxford University guaranteed to give 40kHz . The guys said we humans seem to hear mostly as a digital system , perhaps we detect digital distortion easily because of this ( his words ) . The ear also is a crude analogue device of about 30% THD . On top of that a pulse seems to come back to the ear from the brain which is very fast ( phase lock loop was suggested ) . One other conjecture . The ear produces harmonics very like SE valve amps ( the internal resonance of the chamber ) . Thus as long as it is below 1% THD the ear says that is zero distortion . If the pattern changes slightly we say it is coloured . Thus 1 % or below with linear harmonics zero distortion will be heard . The Naim distortion is almost that and seems contrived ( 1 K + 22K LTP ) . The Naim has slight more 1/3 rd harmonic which gives a dry/ fast sound , my suspicion is not a choice . The Quad 303 seems almost perfect . The 303 is a Quasi design also .
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Old 28th November 2012, 11:58 AM   #1003
Telstar is offline Telstar  Italy
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I think they dont make CFP dual tranasistors because there isn't enough demand? People wants super high gain so they make darlingtons. Idk really, but sounds like a good idea for diy. The discrete semiconductor industry is so f-cked up today...

Quote:
Originally Posted by nigel pearson View Post
The ear produces harmonics very like SE valve amps ( the internal resonance of the chamber ) . Thus as long as it is below 1% THD the ear says that is zero distortion . If the pattern changes slightly we say it is coloured . Thus 1 % or below with linear harmonics zero distortion will be heard . The Naim distortion is almost that and seems contrived ( 1 K + 22K LTP ) . The Naim has slight more 1/3 rd harmonic which gives a dry/ fast sound , my suspicion is not a choice . The Quad 303 seems almost perfect . The 303 is a Quasi design also .
idk... I like good tube amps, but mostly push-pull of triodes with serious iron -the stuff i cannot afford nor dare to build myself. I had a few tech chats with friends and the conclusion seemed to be that vacuum tubes are better because of physics, because the electrons travels much faster in there.
I like fast amps, but I hope for true speed not the fake PRAT induced by 3rd/5th harmonic excess (I'm sure you understand what i mean, NVA for instance).

I remember somebody did some tests and THD of about 0,1% can be heard, less than that guess not, unless is alot of high-order garbage (i believe in the weighted harmonics order).
I do not have much experience in naim sound, besides their cd-players. Have heard only recent top of the line amps and they do sound good, but nothing to yell miracle. Probably more neutral and less fussy with cables than the old ones? Lots of PRAT and slightly dark yet timbrically correct sound is how i describe Naim house sound. I think JV had good ears.

I want to build this "naim NAP clone" because it's a simple circuit, and allows me to try quasi sound. I'd rather use a reputable circuit than some random one found on the net. I'm still young and I'm not sure where my preference will land in the end, but I like to find an explanation of what I hear to the circuitry and the measurements.

I've read all this thread, and it's obvious that somebody liking is not somebody else's (i.e. the inductor at the output -which is something i must try with and without).

It's so true the thing that you said about using cables to connect the output transistors!
I have a mockup switching circuit on breadboard to test 4 different output transistors (yes, CFP, but the drivers stay same, as I dont want to get crazy ) in my headamp. Zero noise pickup or oscillations. Among other things, I hear a different armonic spectrum with different pairs.

uh sorry for long post, this happens when i have lunchbreak early and still some free time
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"The total harmonic distortion is not a measure of the degree of distastefulness to the listener and it is recommended that its use should be discontinued." D. Masa, 1938

Last edited by Telstar; 28th November 2012 at 12:02 PM. Reason: spelling/typos
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Old 28th November 2012, 12:59 PM   #1004
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What I like about this tread is people seem to have enough knowledge . They ask themselves what sound they like . Some seem to know too much and are listening without the need to listen when reading other threads in other places .

I went in to our local Maplin store and met a very nice chap called John . He said they have a customer called Mr Know It All . From John's description he seems to know all the cliches . I said I am Mr Know Nothing Much because I just about know enough to get along .

With valve amps the transformers are a problem .
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Old 29th November 2012, 02:08 AM   #1005
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Quote:
Originally Posted by Telstar View Post
Yes please, I know one guy that can etch a good pcb (and with silkscreen too that would help me not making mistakes ).

I'm not in a hurry to build it, though, and it will be interesting to hear your opinion on Greg's mods.
Hello
I do not have silkscreen since all my PC boards are hand drew-it.
I can give you the size of the PC board, the color codes, I can make a picture from my stuffed board etc.
That is the best I can do. Also you can ask me in case something not clear to you.
Again I do not have silkscreen , I'm sorry.
Please let me know if that good enough to you.
Thank you
Greetings Gabor
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Old 19th December 2012, 07:50 PM   #1006
Spuds is offline Spuds  South Africa
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My almost completed amp.

Click the image to open in full size.
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Old 19th December 2012, 10:04 PM   #1007
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Nice, short wiring there. Have you powered it up yet and checked for hum, noise?
It is never simple to do your own arrangement of boards and power supply so it would
be interesting and helpful to others to hear how successful you were mounting the
amplifiers on the transformers and also squeezing the valve preamp. section supply in.

Good work and BTW, what TO3 transistors are you using for power output?
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Old 20th December 2012, 05:56 AM   #1008
Spuds is offline Spuds  South Africa
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Quote:
Originally Posted by Ian Finch View Post
Nice, short wiring there. Have you powered it up yet and checked for hum, noise?
It is never simple to do your own arrangement of boards and power supply so it would
be interesting and helpful to others to hear how successful you were mounting the
amplifiers on the transformers and also squeezing the valve preamp. section supply in.

Good work and BTW, what TO3 transistors are you using for power output?
Powered up and the only noise it had was a some nasty valve hiss. That's all gone since I added the volume control.

The previous way I had it wired, I could hear my hear beat coming through each time I brought my hands near the signal wires.

Overall it's now VERY quiet, but will still be adding some additional shielding for the transformers and PSU's.

I'm using the BUV20's for the output transistors.
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Old 20th December 2012, 12:10 PM   #1009
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Hi Spuds , I love it . It is so much like things I do I had to look twice .

BUV 20 . 125 V 50A 8 MHz !!!!! Great for NAP250 clone ( BDY56 as was ) . 50 A !!!!!

Happy Christmas all .

Nigel
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Old 20th December 2012, 12:16 PM   #1010
Spuds is offline Spuds  South Africa
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Quote:
Originally Posted by nigel pearson View Post
Hi Spuds , I love it . It is so much like things I do I had to look twice .

BUV 20 . 125 V 50A 8 MHz !!!!! Great for NAP250 clone ( BDY56 as was ) . 50 A !!!!!

Happy Christmas all .

Nigel
Thank you.

I am currently busy with 2 of these, hopefully they're both going to be done by the end of January.
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