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Old 24th February 2005, 11:12 PM   #1111
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I'm all ears... what is it exactly what you did,... can you post a schematic?

gr,
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Old 25th February 2005, 12:31 AM   #1112
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Quote:
Originally posted by jacco vermeulen
There is company here in Holland that builds amplifiers under the name Array.

The amplifiers have an encridible number of paralleled small power devices, they claim sonic benefit.
I built a nice little amp some years ago (last seen in the
possession of Bob Lord) which consisted of arrays of TO-92
devices (a hundred or so) each operating at about 10 mA,
Class A of course. He loved them, but not enough to buy a
second pair.

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Old 25th February 2005, 01:06 AM   #1113
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Nelson i was thinking about putting a hundred or two of bc559 working togheter, since there is so many the heathsink is not an issue, in fact not needed at all right?


about my listening impressions, and level of detail, i have a very nice MD recording of cindy lauper, in the song altrought the night
you can hear the soft sound of her tongue hiting the lips and tooth while she is singing and pronouncig the "th" sound, i was able to hear that only in a class A GOOD amp.

my schematic is very simple, the doz of rod eliot, but instead of paraleling 2 tip3055 i have paralleled 22 bd139.

just conecting them togheter, of course i put a resistor in each emiter 1 ohm resistor, this could seem large , but there is so many devices that i doesnt matter.
i can describe in another way the sound:

when you are adjustind the quiescent current , and the quiescent current is too smal the amp sounds awfull, like a trash can, as you increase the iq sound is more detailled an more authoritative,
well that whats happened, when i shifted the 3ºpairs of tip3055 for the bunch of bd139 with the same current, the impresion was the same than i have explained before, and "saddly" when i think of what my amp used to sound before, i think the sound was like a "trashcan" .

i wonder if i replace the bunch of bd139, by 10 times more bc559, will the amp sound even better?



i like to know wich was the kind of a classA circuite you used Nelson single ended i presume but no mosfets in it right?

and i also like to know the more important reason of why the amp
sonds actually better, is there any 2d order harmonics effect?

personnaly i don't think so because the saound is more warm but also more "fine"...if i close my eyes i can even feel the lips of carly simon vibrating...
i can hear as i have said before clearly the sound of te tongue softly hiting the lips an then the tooth,that is for real!



Maybe the reason is more likely to be the statistical reason i have outlined before the , way that when the size of the sample of a given population is somewhat near 30 then the distribution tends rapidly to be gaussian distribution , with a clear maximum near the center, not like the t-student that is used for smaller sampling sizes.
that is one of the reason why in the school even if each student has a bad voice, the whole class singing toghether sonds almost always fine ( but there i admit there is a loss of resolution so this theory lacks something important)
Maybe someone can show us some light on the concept itself?

thanks to all that are interested by this and will give their opinion
(i apologize for my poor english , i can speak correctly only french and spanish)

see you soon friends!

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Old 25th February 2005, 02:39 AM   #1114
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Did you make a pc board for this, or use prototype? If you have aboard, can you post it. Sounds like fun.
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Old 25th February 2005, 03:04 AM   #1115
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why do something that has already be well done?

http://diyaudio.8m.com/Bebet/bebet_sch.html

this page is ok
but do NOT put paralleled transistor as this author said
to paralel them use only one resistor in the emiter conection.
(the author uses somewhere else a resistor in the colector too, this is not a good thing to do)


there is one pair of transistor to paralel another pair just conect base to base, colector to colector , and emitor to a resistor then to the correspondig pcb conector.

very easy project, hope you can complete it soon to exchange opinions
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Old 25th February 2005, 03:18 AM   #1116
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The ols National LM395 "super transistor" was based on putting a bunch of teensy devices in parallel. I wonder how (or if) it would work in this application. Unfortunately, it's available in only one sex, but the A40 gets along pretty well that way...
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Old 25th February 2005, 06:14 AM   #1117
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Hi ericfe,

Why not try a single or two 2SC5200 in place of all those BDs.

That Toshiba is a good one in the class-A circuit.


Cheers ........... Graham.
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Old 25th February 2005, 06:33 AM   #1118
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Quote:
Originally posted by Nelson Pass
I built a nice little amp some years ago (last seen in the
possession of Bob Lord) which consisted of arrays of TO-92
devices (a hundred or so) each operating at about 10 mA,
Class A of course.
Did it have the Pass Labs trade mark on it ?

"Some years ago" would incline that the TO-92's were Mosfets ?
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Old 25th February 2005, 07:04 AM   #1119
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hello Graham,

here i am posting some benefits of replacing ONE power device by several , as much as possible , much smaller devices,
that is all about this...

until now i have used only 3 paralelled power devices, but now i can see that benefits of paralleling a lot of "small power devices"

11 pairs are just enough but i like to have a good reserve of power in my outpute devices so i calculated in a total of 24 pairs of bd139.

and a as future project , i am considering to put 200 bd560 working in paralel, for a class a this will be a sure benefit as for clss ab. but we have to take care of stability i know....

some exeprimenting is still necessary.

further more i hve bught the toshiba you are talking about in 4 differents shops, all were fake . so i wil never use again those.

any new idea or explanation is welcome.





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Old 25th February 2005, 08:03 AM   #1120
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Hi ericfe,

Try a credit card order to Cricklewood Electronics in London.

They are on the 'net and do not add more than minimum costs for postage.

(Wait till I've ordered more for myself though.)

Cheers ........ Graham.
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