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Old 16th June 2012, 01:00 PM   #1
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Default Class A amp with fully symmetric design using only NPN output transistor

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
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Old 16th June 2012, 01:57 PM   #2
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Quote:
Originally Posted by muddasirwaheedmalik View Post
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
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Old 16th June 2012, 01:59 PM   #3
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Quote:
Originally Posted by muddasirwaheedmalik View Post
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.
Quote:
Originally Posted by muddasirwaheedmalik View Post
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:
Click the image to open in full size.
... 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.
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Old 16th June 2012, 02:07 PM   #4
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Any schmematics , minimal parts, only symmetry CLASS A. ?
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Old 16th June 2012, 02:15 PM   #5
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Quote:
Originally Posted by muddasirwaheedmalik View Post
Any schmematics , minimal parts, only symmetry CLASS A. ?
If you are going to use only NPN output devices, then the "symmetry" bit is going to be real challenge.

Symmetrical is not necessarily good.
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Old 16th June 2012, 02:32 PM   #6
knutn is offline knutn  Norway
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Quote:
Originally Posted by muddasirwaheedmalik View Post
Hi i intend to make a 200-600W pure Class A amp.
For 600 W output power (8 ohms), your push pull amplifier will dissipate more than 1200W, have a quiescent current of more than 6 Amperes, and the power supply rails will be more than plus/minus 100 Volts. I really look forward to see your well-sounding oven....
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Old 16th June 2012, 03:01 PM   #7
qusp is offline qusp  Australia
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this is something like what a 600W Class A amplifier will look like, if you are lucky =)

Click the image to open in full size.

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
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Old 16th June 2012, 03:15 PM   #8
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This one (19" - 5U) is for a project to come, but it will handle not much more than 2 x 60 watt class A.

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
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Old 16th June 2012, 03:36 PM   #9
qusp is offline qusp  Australia
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Originally Posted by pieter t View Post
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
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?

Click the image to open in full size.
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Old 16th June 2012, 03:47 PM   #10
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perhaps hes building something like these?

Click the image to open in full size.
Insane
But large speakers can be high efficient and play great music with low power tube amps...
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