Class A amp with fully symmetric design using only NPN output transistor

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Hi i intend to make a 200-600W pure Class A amp.
My limited knowledge has limited to ouput device matching.
My best shot is a stock of 2SC5200 transistors.
Is there any simple design for class A pull push type using only NPN in output stage?
Reason:available 5200 transitors, 48 of them and no dismilarity in turn-0n turn off time associated with complimentary pair.

regards
 
Hi i intend to make a 200-600W pure Class A amp.
Is there any simple design for class A pull push type using only NPN in output stage?
regards

It is perfectly possible to make a push-pull Class A amp with only NPN output devices. You simply use a quasi-complementary output stage, preferably with a Baxandall diode to reduce distortion.

You will find more info in my power amplifier book, (5th edition) page309.

The Audio Power Amplifier Design Handbook
 
Hi i intend to make a 200-600W pure Class A amp.
That'll be a fabulous room heater.
Not to mention exceptionally big and heavy.
My limited knowledge has limited to ouput device matching.
My best shot is a stock of 2SC5200 transistors.
Is there any simple design for class A pull push type using only NPN in output stage?
Reason:available 5200 transitors, 48 of them and no dismilarity in turn-0n turn off time associated with complimentary pair.
Here's an output stage variation for the Leach amp:
outstage3.gif

... as discussed here.

Q14/15 would be medium power, Q16/17 5200s, and Q18/19 plus corresponding Rs would be replicated in parallel, again with 5200s. Not sure how many you can realistically drive, 4 or 5 pairs seem common - maybe twice that max.
 
this is something like what a 600W Class A amplifier will look like, if you are lucky =)

An externally hosted image should be here but it was not working when we last tested it.


Dimensions : 19" Rack Mountable 5U high (220mm / 8.7")
Overall Depth : 545mm (21.4")
Front Panel & Handles : 75mm (3")
Rear Handles : 40mm (1.6")
Amplifier Body : 430mm (16.9")
Weight : 40kg approx.

this is a 4 way amp though, with crossover and is 850w

Specifications

Output Power (RMS) :
HF: 100 Watts into 6 ohms
MF: 200 Watts into 16 ohms
LF: 275 Watts x 2 into 8 ohms
 
This one (19" - 5U)
I am curious why, and for what purpose, people intend to make a 200-600 watt class A amplifier.
I guess the OT means class A/B :confused:
i'm curious too, my guess is hes not aware of exactly what the implications of that is, thus my including a picture of 1 channel

perhaps hes building something like these?

An externally hosted image should be here but it was not working when we last tested it.
 
my gosh, those are speakers.

I agree with Doug, symmetrical is not what I'd be aiming for if I were looking at all NPN outputs.

Have you considered a JLH style amplifier ?

You may find this a useful link: The Class-A Amplifier Site

and you can get PCB's for it from ebay etc.

You can scale it up using multiple outputs - but I would suggest that 40W would be reasonable. If you really want 200W plus then using up existing output transistors is the least of your challenges - you'll need a humongous heatsink, a huge power transformer, a soft start circuit, thermal protection etc.

If this level of power is a 'must' then I would recommend ClassAB instead. There are many good approaches. Doug has published a few :D
 
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Hi i intend to make a 200-600W pure Class A amp.
regards

It is worth bearing in mind that with a real musical signal, as opposed to sinewaves, the maximum efficiency will be around 1% at full throttle. (Just clipping) It will be essentially a 1200W room heater.

I do not encourage people to build large Class-A amplifiers. They are grotesquely inefficient, and that offends my engineering sensibilities.
 
Assuming a multi-driver system, at that level an active crossover must be considered. There are few single drivers that require that much power except for subs. I don't require class-A subs. But I digress. What I wanted to suggest for those transistors, if you really love class-a, is making many amp channels of smaller wattage. You can tri-amp, or you can use redundant drivers each with its own amp, or perhaps someday use them for home theater surround. At the least, the improved efficiency from using an active crossover makes the idle current draw more reasonable.
 
ok dears.

I have a very good focal car amplifier. To save the hastle i am going to use the amp output to drive a high bias Class A output stage using 2SC5200 and 2SA1943 10 pairs.

the amplifier is a car amplifier and for output stage i have a +/-50 V invtrter off 12 Volt. my target is 2000 W Class A.

Now i have an amp for which i intend to separate the pull push output stage ground the emitters of NPN and PNP output transistors with 10K resistors to ground for feedback, and feed the 8 pull push pairs at +/- 50 V rail (10 pairs of 2SC5200 and 2SA1943) with the out put devices of the amplifier which incidently are also the same pair)

Questions:

What should be be the base resitance feeding the output transistors
Is 2 Amp Quisescent Ic enough for the Class A operation per device
for paralleling devices i intend to use 0.2Ohm 5 watt resistor in emitters.
Is any feed back from this output stage required?

Regards. Its just an intersting attempt just to add to the output stage of an existing high end car amplifier.

Regards
 
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