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Old 18th December 2009, 05:54 PM   #91
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Hi Eva,
thatīs a weird designation, I know. When optimizing transistors for some application (switching, video, current amplification, HF, and so on), comparatively, certain qualities will inevitably be degraded. You can`t have everything at the same time. A change in one parameter will effect a large number of other parameters. A highly-accurate manufacturing process is equally important and no one can beat the Japanese technology. You see, it`s pointless studying the data sheet if you actually have something else on hand.
To be continued...
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Old 18th December 2009, 05:56 PM   #92
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I have heard a wide range of comercial audio hifi power amplifiers. Such with low speed low Ft devices (MJE340/350 for VAS/predriver and 2N3055/MJ3055 and MJ15003/15004 in the power output stage) and such with high speed and very high ft (go to post #1 fore some examples)
But until this day I cannot confirm, that amplifier stages equipped with last kind of semiconductors definitely sounds better.
I recall follow:
To investigate sound effects I have built in some years ago different semiconductor types by two faulty exemplares of an "A1" from Musical Fidelity (only power amp unit), a special circuit developed from Mr. Tim de PARAVICINI - go to
Musical Fidelity A1 - Technical

The output stage runs with an idle current of 350mA
First exemplare I fitted with old Motorola versions of MJ2955/2N3055 and second with 2SA1095/2SC2565 from Toshiba (a little trouble through other outline). Because the supply voltage is low, most power devices would be match. As long as the speaker current was below arround 700 mA, there are no audible different. Otherwise (i. e. above this current value) by the version with Toshiba's 2SA1095/2SC2565 I note very slightly advantages (a little bit less harshness THD-Value identical, but less low-order and little more high order distortion).
With an idle current reduction to 100 mA, the same effect was observed, even at small volume. By compare of both exemplares in that kind, that I use 350mA idle current by the MJ/2N and 100mA by the 2SA/2SC, this one with 350mA sounds clearly better (in this case I have compare classA to class AB).

Unfortunately I have not make documentation about this, because I haven't cad supported distortion measurement equipment.

But it is to assume, that high ft by power devices only exhibit slightly audible advantages by typical A/B output stages and not by class-A.

But in generall, all in all, should not be overlooked that the quality of circuit development and the PCB layout developement significantly greater influence on the final sonic and measure result than the fact, whether fast Japanese (special made for audio) or slow American or European power devices are in use !!!

The proof is simple. A very well-developed power amplifier circuit (especially, if there is Class-A) with the vintage-2N3055 or older MJ types - still in production, is still hard to beat, even with the best today's available power devices for audio.

If they have very reliable P-Spice parameters, it must be possible through simulatiom, even with transistors that are not designed for typical audio applications to achieve superior sonic transmission results and low IM/THD

Last edited by tiefbassuebertr; 18th December 2009 at 06:08 PM.
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Old 18th December 2009, 06:12 PM   #93
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Let me see, I had a second look to try understand how the information should be interpreted given in the data sheet and test circuit in attachment of post #71

It says 28,3 V RMS and 100 Watt @ output into 8 Ohm..
Let's see if we do the Ohms law calculation the 28,3^2 = 800...
P = U^2/R >>> 800/8 = 100 Watt
Upk (for sine) = U RMS * sqr2 >>> 28,3 * 1,414 = 40 Volt peak

alternatively we can calculate the power also as follow:

28,3 U RMS / 8 Ohm = ~3,54 A RMS
28,3 * 3,54 = 100 Watt

As I can see we have 10 Volts of headroom to the 50 Volt rails supply before clipping occures.

Wahab, correct me if I'm wrong here!?

If we do the simulation again with 80 Volt pk-2-pk and for both 240 mA and 52 mA what how would the distortion look then?
(Re for output transistor as in pots #71, eg. 0,5 Ohm)

Cheers Michael

Last edited by Ultima Thule; 18th December 2009 at 06:19 PM.
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Old 18th December 2009, 06:20 PM   #94
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tiefbassuebertr,
device type is just one condition. However, if you cant hear differences, go always with the cheapest you can find on eBay.
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Old 18th December 2009, 06:25 PM   #95
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Quote:
Originally Posted by Lumba Ogir View Post
Bob,
the audio market is very small, the switch market is very big, now why on earth would ON-Semi suddenly start developing devices for audio?
This is a specious argument. They DO in fact make transistors for audio. Just ask Charles Hansen. You are apparently unaware of the thermal bias stability issues in BJT output stages that these transistors greatly mitigate.

Cheers,
Bob
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Old 18th December 2009, 06:30 PM   #96
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Quote:
Originally Posted by Lumba Ogir View Post
Damon Hill,
yes, using switch die design processes all over.
You know not of what you speak. Have you worked at Moto? BTW, not all transistors designed primarily for the switching market are unsuitable for audio. This same ignorance applies to those who think you cannot make a good audio amplifier out of HEXFET vertical MOSFETs. Ask Nelson Pass. You are dealing in too many bland generalities.

Cheers,
Bob
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Old 18th December 2009, 06:36 PM   #97
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I would have thought that the MF A1 runs normally at considerably greater quiescent current than 350mA....
I used to work for MF and I well recall carrying out tests one day to see if it really was class A.
From memory, it gave about 14Watts RMS per channel in class A.
The surprise was the A370 which gave only 18W RMS in class A! A bit less than the often touted 185W!!
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Old 18th December 2009, 08:05 PM   #98
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Quote:
Video transistors often have very low gain and very non-linear Ic/Vce curves.
As usual, I strongly disagree. The essential device properties for video and voltage amplification coincide. Please take a look at the data sheet of the earlier mentioned 2SC3600/2SA1406 as a good example, some features will not be immediately apparent.
This matter would require a comprehensive answer, you should have followed the discussions about it in the other threads.
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Old 18th December 2009, 08:10 PM   #99
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Quote:
Steve,

Yes, but my post concerned post #71, or perhaps do you know what is the Iq?
Post 70 shows the IQ 240ma printed on the graph. I do not believe there is information in post 71 to arrive at this figure.
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Old 18th December 2009, 08:30 PM   #100
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Lumba

Since this thread is about audio power output stages what about comparing 2SA1943/2SC5200 with onsemi 3281/1302?
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