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Old 18th March 2013, 08:12 AM   #8691
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yes fully aware of Hitachi's entry into comp market and HMA's.. just Perreaux's website regarding their "Histoty" refutes this claiming to be "First"( suggest a read made me laugh) but as an experimental designer as one does when studying I used the Sony devices first though not A MOSFET just a FET of the vertical type way before 2SK134/J48's.
My point if Perreuax will tell "Porkies" about being "1st" what other economies do the give or any other maker for that matter still even if the "Specs" are real or made up by the Marketing dept it has little or nothing to do with the spec in this case just Subjective opinion or perception which IMO is all that countsI rent and install Pro-audio not one item gets on my stock list unless I like it regardless of specs. a lot of kit has arguably good or excellent specs but sounds rubbish. I can remember talking to amongst others Bob Carver about his reseach into "Transfer Function" which has very little to do with measured results we would usually associate with performance the same topology with different parameters but "measuring" virtually the same sounding so very different.
Specs mean little about real-world performance to the ear hence your liking the Perreauh/KEF combo using a basic 5 BJT consisting of only a differential pair a current source and a curent mirror driving that bank of MOSFETSwith virtually no stablising of the driver part running on unregulated rails which would usually give a "bad" spec. ...So measured specs or sonics er toss a coin!!!
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Old 18th March 2013, 10:36 AM   #8692
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My memory says it was Sony who used V-FET's ( TA 5650 was a domestic version and very nice ) . MOS FET's v V FET's . One can always find unique selling points . Mr H C Lin patent for these FET's is dated 1969 ( Silver Springs MA ) .

Feedback paths being 9 mm was the critical parameter I referred to . I can not imagine the speed of light comes into this ? That is I suspect the belief system that is being promoted here ? If I am wrong let me know . If you say it gets other things right I did already say that . The way feedback is arranged is critical . the spectrum analyzer will say that . Doing all the right things for all the wrong explanations . I do this sometimes . I discover something and keep my mouth shut . It is then promoted using existing concepts .
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Old 18th March 2013, 12:09 PM   #8693
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Quote:
Originally Posted by nigel pearson View Post
Feedback paths being 9 mm was the critical parameter I referred to . I can not imagine the speed of light comes into this ? That is I suspect the belief system that is being promoted here ? If I am wrong let me know . If you say it gets other things right I did already say that . The way feedback is arranged is critical . the spectrum analyzer will say that . Doing all the right things for all the wrong explanations
The vagaries of electronics come into it - an extremely short path means that stray inductance, capacitance and RF pickup is minimised, the reason why SMD is good for really high speed and sensitive circuitry. My DIY gainclone used about the same distance, for the same reasons.

If someone wants to come with hokey reasons, for marketing, then that's their call ...

@dvv: yes, everything counts, but I look at audio in a subtractive, not additive, light. To me, every system is really "perfect", on the "inside", but to get that happening the problems have to be subtracted. Find the worst problem, subtract that effect by a fix or workaround, find the next, etc; continue until the SQ is acceptable. I find I get, for me, dramatic improvements with that approach.

Frank
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Old 18th March 2013, 12:30 PM   #8694
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Frank , thanks for that . I want to get as much discussion on this as I can . I feel the short feedback path is important . Short in itself may be incidental ( resistance or time effects that is ) ?

Very interested in the supposed emergence of upper harmonics if using greater amounts of feedback . The expression all other things being equal springs to mind . And they never are in real life . An amplifier happy with 20 dB of feedback may not be so happy at 40 dB . Already the pattern of distortion changes due to action require for stability . I was also interested in the effects of noise . Could it be that any distortion which is in noise effectively doesn't exist ? That is like dither it has asked the transistor to make a choice ? We are talking crossover distortion if so . Other distortions do not interest me as much . Usually these are well under control .
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Old 18th March 2013, 01:42 PM   #8695
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You don't necessarily need thick metal, except when your design assumes superconductors everywhere (like Spice does?). If you assume every connection has some resistance and inductance, and design accordingly, then you can use ordinary wires. So the bigger improvement you get by scattering copper, the worse was the original design.
I will drink to that . I guess some extra copper in the 0V connections usually will do no harm ? It will cost nothing in terms of materials and time . Keeping standing current down is useful ? Or maybe not . If reveled at higher current it might be that alone that alerts someone to a problem . If so turn the bias up and have a measure . Turn it down latter .
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Old 18th March 2013, 06:56 PM   #8696
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Nige,

By definition, shorter signal paths are welcome, no matter what you are making, and with which components. Obviously, this also applies to the feedback path. However, that may not always be practical to do; it's like sorting things in a cupboard, not everything can be up front, something has to be down below.

Which means that planning your outlay is, in my view, by far the most important single item influencing the end result.

Folding a circuit - having a part of the circuit on a verically mounted separate board, its pins being soldered down in the "motherboard", is sometimes a good way to go to keep everything compact.

Another aspect is to plan for double sided PCB, with the top side having a lot of ground plane on it. Ask the RF boys, they excell at it because they have to. That also allows you for wider traces for the rest.

Lastly, what about the actual glass fibre boards? The industry standard is 30-35 microns of copper, and it's known to work. You can move n up to the 50 micron class, or like me, go up to the 70 micron class. 70 micron copper is about what you can buy easily, the 120 micron ans 150 micron are very hard to come by, and are damn expensive.

The killer end move is having all your through holes metalized. That is about as good a contact as you can hope for without resorting to NASA technology. It's not very expensive.

Before soldering, clean every contact leg of whatever with some cotton and medicinal alcohol. I know they look shiny and clean, but in fact may not be quite so. If you want to go bonkers extreme, sandpaper each contact leg with very fine sandpaper, clean up with said alcohol and gently spead solder from top to bottom BEFORE soldering on anything. That should if not stop corrosion, then at least that will delay it by a couple of years and give you the best possible solder point ever.

Obviously, you will be doing that only on the final form of whatever. It takes a lot of time.
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Last edited by dvv; 18th March 2013 at 06:59 PM.
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Old 18th March 2013, 08:09 PM   #8697
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Quote:
Originally Posted by nigel pearson View Post
My memory says it was Sony who used V-FET's ( TA 5650 was a domestic version and very nice ) . MOS FET's v V FET's . One can always find unique selling points . Mr H C Lin patent for these FET's is dated 1969 ( Silver Springs MA ) ...

.
In 1975, Sony introduced their two integrated VFET amplifiers, models TA-8650 and TA-5650.

In the same season, Yamaha introduced their C1 and B1 pre and power amp, also based on VFETs.

It's a moot point who was actualy THE first, as both appeared in the same season, based on completely indepndent research.

The rise of Hitachi's MOSFEts marked the first truly economically viable power devices, which were found to be quite reliable and easier to work with that previous versions from other sources. First models were the 6500 series, which lived on until 1989 in different guises and were much more elaborate than the original version.

Unfortunately, their versions of VFETs were very expensive to manufacture, and both suffered from reliability issues for the first year of production or so.
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Old 18th March 2013, 08:58 PM   #8698
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Originally Posted by nigel pearson
I guess some extra copper in the 0V connections usually will do no harm ?
Adding copper could couple circuits which should be separate, if a Tee junction gets too broad so currents flow in a slightly different way. As in other branches of engineering, there is no magic bullet. To modify a circuit successfully, you generally have to be smarter than the original designer so you can spot his mistakes/economies and improve them. If you are smarter than him, why not design your own circuit?
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Old 18th March 2013, 10:19 PM   #8699
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I'm with dvv on where the real gains can be made -- I have only a low level interest in topologies; whether MOSFETs or BJTs, or TMC or TPC, etc, is "better" - these are all in the area of the 5 or 10% gains I mentioned before. It's about being really fussy about getting what you've finally decided on using to really work properly, that's where the major action is, as far as I'm concerned.

Technically brilliant circuits can sound awful; mid-fi "muck" can take your breath away if they're properly tuned -- it's as simple as that ...

Frank
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Old 19th March 2013, 12:40 AM   #8700
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