Something to consider is that On-Semi transistors almost always have much higher capacitances than similar Japanese ones, even the high Ft ones. This may have to do with the lower Ft (again, even "high Ft" On-Semis don't have such a high Ft).
I don't know why capacitance is always a few times higher, maybe they just use bigger dies, or they need bigger dies for the same SOA, or their fabrication process results in higher capacitances, or just they don't optimize capacitances at all
(I think the last option).
Several times I had to increase miller capacitance when replacing dead On-Semi (Motorola) MJE340&MJE350 VAS and pre-drivers by Philips ones (no other brand available) in order to make the amplifiers stable again. If I remember properly, the ones from Philips also had higher hFE (and probably 5-10 times higher Ft... Philips seems like the opposite example, they always seem to do everything with as little silicon as possible, Japanese seem to be in the middle )
I don't know why capacitance is always a few times higher, maybe they just use bigger dies, or they need bigger dies for the same SOA, or their fabrication process results in higher capacitances, or just they don't optimize capacitances at all
(I think the last option).Several times I had to increase miller capacitance when replacing dead On-Semi (Motorola) MJE340&MJE350 VAS and pre-drivers by Philips ones (no other brand available) in order to make the amplifiers stable again. If I remember properly, the ones from Philips also had higher hFE (and probably 5-10 times higher Ft... Philips seems like the opposite example, they always seem to do everything with as little silicon as possible, Japanese seem to be in the middle
)
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"...slightly improved 2N3055" ??? But which 2N3055 ?? There are a wide range of different 2N3055, here some examples:
2N3055 Datasheet pdf - COMPLEMENTARY SILICON POWER TRANSISTORS - ST Microelectronics
and
2N3055 datasheet and Application Note, Data Sheet, Circuit, PDF, Pinout | Datasheet Archive
The 2N3055 from Semelab e. g. was prefer from certainly british high end audio products like Naim Audio (with custom specific type No). The transit frequency was much more higher than the usual value for this type (mostly 800 - 1000 KHz).
please read also this:
http://en.wikipedia.org/wiki/2N3055
and this
http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=960371
I would like to see one of RCA's first advertising photos and slogans from the time of introducing
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Compare datasheets (SOAR, Uceo,linearity- h21vs. Ic..) If it is "slightly" improved..Yes, MJL´s are not too fast, but fast enough for very good audio amplifiers, and they are very rugged and reliable, are not prone to parasitic oscilations, very stable, without base stoppers (better linearity) too.
That's actually true. In the old days when all you could get were 5MHz devices (even the Toshiba 2SD424) you had to use output triples if you wanted more than 100 watts or so or distortion would go through the roof. With the higher fT/linearity outputs and drivers you can get from Toshiba and Sanken now you can get away with just two current gain stages - all the way to 1200 watts or so. You just can't do that with the MJ's which don't have as good a beta linearity. And you don't "need" a triple at the more-normal 200W level anymore.
Of course, I'll still use a triple on anything over 55V rails myself, but I'm not trying to save 50 cents on a pair of TO-126 predrivers. Most manufacturers will up-end the universe trying to save those pennies.
So the japanese manufacturers build their parts according to someones or yours 'ear scale'?
Do Toshiba or Sanken do their quality control by listening?
Regards
Lumba, if You preferred "rich, warm, musical..." sound (with high level of low order distortion and IMD product) , it is OK, it is Your taste.. But then please talk not about technical facts as linearity and technology of "switching" devices, and especially not about "linearity according to the ear`s own scale" .
PMA had made on our local forum test, he posted recording with various levels of low order added distortion (without information what he made) . Even "golden ears" cannot hear and tell what is diference between tracks, and distortion levels was about 1% and more .
You are right in one point, measurements say nothing, but only about personal preferences. They can tell quite all about objective performance , off course not single 1kHz THD+N measurement.
. PMA had made on our local forum test, he posted recording with various levels of low order added distortion (without information what he made) . Even "golden ears" cannot hear and tell what is diference between tracks, and distortion levels was about 1% and more .
You are right in one point, measurements say nothing, but only about personal preferences. They can tell quite all about objective performance , off course not single 1kHz THD+N measurement.
In case of the traditional measuring methodes (THD 1000 Hz, IM 19/20KHz) you are right.
But with the appropriate measurements, I would get a fairly accurate statement about the amp sound character without having heard him oneself.
Unfortunately, it is so, that nobody uses such measuring methods. Or even so that nobody wants to use such methods of measurement. Thus, discussion like this are still present by this forum, but also in others.
An easy way to find out an exactly attestation regarded different sonic quality (and different distortion measurement) through different ft's and different emitter structures would be to create a ordinary complementary push pull darlington power follower without front end for voltage gain in the NFB loop, so that only the NFB through the follower topology itself have an effect (open loop gain not too high). The schematic by the Densen-thread here about
http://www.diyaudio.com/forums/solid-state/114865-densen-amp.html
is a good topology therefore, if one remove the first stage of power buffer (please ignore the second schematic version).
The test must perform by two modes: pure Class-A and Class AB (20-50mA through the output devices).
Perhaps one of the members can perform and investigate this.
I recall a similar test report, where the old 2N3055 has been compared with modern parts of power devices (perhaps JLH-ClassA?) Unfortunately I have forget the download place in the web.
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I have shown a few times why I can't agree with that statement.
It's down to peak current delivery into reactive loads.
200W into 4r0 (within your limits of +-55Vdc) requires Vpk = 40Vpk and Ipk = 10Apk.
Into 4 ohm speaker load this demand can rise to around 30Apk.
This cannot be met from a two stage output EF not even with double complementary pairs in the final stage.
The peak current demand for 200W into 8ohms is not nearly as difficult to meet but it is way outside your +-55Vdc supply rail limit.
Juergen,
They don`t. Moreover, data sheets specifications do not signify sonic properties, but 80MHz is more promising than 4MHz. The general bandwidth / linearity relationship is known. Ultimately, a practical evaluation will tell, that can be done easily and reliably, no musical skills, no golden ears, all you need is a change in attitude.
it s quite doable...i use darlingtons MP1620/MN2488 with a beta of 6500 mini
at 7 A, and they are the second grade ,the first being 15000 mini....
using four in paralele, wich is a minimum for an amp.
loaded with 4R, it can provide the 30 amps with 4.6 mA of
total base current and 2 mA , respectively for the second and first
grades...
all is question of choice of components...sure that if you
use the classical beasts as the onsemi mjl + mje , it will fall short..
I have not even bothered to look at the datasheet, but I will guarantee that this integrated Darlington will not perform as a well as a pair of Darlington connected discrete BJTs, over a range of realistic output currents.
The right approach for this you will find in this topology of Dynacord's stage power amp L-1600 resp. EV (Electro Voice) P2000 (still available) go to Owner's Manual for datas
http://www.electrovoice.com/documents/ev/p2000-eds.pdf
and the attachements (some schematics)