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Old 11th September 2013, 04:12 PM   #1
Gost22 is offline Gost22  Bolivia
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Unhappy Audio amplifier with 2n3005

Hi guys!
View schemeatics this amplifier for which the author gives this
Specifications:

Power output is 60 watts into 8 Ω and 100 watts into 4 Ω loudspeaker.
Total harmonic distortion is less than 0.01 %.
Frequency range is within 20 Hz and 20 kHz.
The input sensitivity is in the vicinity of 750 mV.
The frequency characteristics lie in between 1 dB from 15 Hz to around 100 kHz.
If all this is okay?! What changes in the schematic needs to be done for this audio amlifier with power supply Ucc=+/-38V and with the output transistors MJ15003/MJ15004?
Thank you for your cooperation!
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Attached Files
File Type: doc Parts List-1.doc (19.5 KB, 37 views)

Last edited by Gost22; 11th September 2013 at 04:26 PM.
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Old 11th September 2013, 04:59 PM   #2
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Supposing the transistors can support the voltages and currents, I don't see any important mod, perhaps R4 and R5 to maintain current in leds. The other parts are feed in constant current, so no mod necessary. Check also capacitor voltages rating (50V, mainly C6, C7 and C5).

But the schematic looks some strange. Did you forget R and a C in series from left side of R9 to ground? As is, the amplifier is unity gain.
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Old 11th September 2013, 07:45 PM   #3
jaycee is offline jaycee  United Kingdom
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If you can use NPN/PNP power output transistors then you dont really need a quasi-complimentary circuit like this one. A basic Blameless type circuit will work fine.
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Old 12th September 2013, 12:05 AM   #4
Gost22 is offline Gost22  Bolivia
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Quote:
Originally Posted by jaycee View Post
If you can use NPN/PNP power output transistors then you dont really need a quasi-complimentary circuit like this one. A basic Blameless type circuit will work fine.
What are the transistors in the schematic?
thank you!
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Old 12th September 2013, 02:32 AM   #5
jaycee is offline jaycee  United Kingdom
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They aren't specified but the following should work:

TR1,2,3 = BC556
TR4 = MJE340
TR5 = MJE350
TR6 = MJE15032
TR7 = MJ15003
TR8 = MJE15033
TR9 = MJ15004
TR10,11,12 = BC546
TR13 = BD139 (mount on main heatsink)
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Old 12th September 2013, 03:40 AM   #6
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The schematic in post#1 is very similar to a circuit published in Elektor just after the release of the Crescendo and Mini Crescendo designs, except that instead of LEDs, the CCS were referenced with zener diodes. I had built several of those amps and thought they sounded very good for their time, especially with a fully regulated PSU.
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Old 12th September 2013, 04:24 AM   #7
Gost22 is offline Gost22  Bolivia
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Quote:
Originally Posted by Samuel Jayaraj View Post
The schematic in post#1 is very similar to a circuit published in Elektor just after the release of the Crescendo and Mini Crescendo designs, except that instead of LEDs, the CCS were referenced with zener diodes. I had built several of those amps and thought they sounded very good for their time, especially with a fully regulated PSU.
Hi Samuel!
If you are unable to view the schematics.
thank you!
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Old 12th September 2013, 05:45 AM   #8
Gost22 is offline Gost22  Bolivia
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Default PCB for this audio amplifier

Hello!
Mr. Yaycee please show your PCB for this audio amp if you have one.
Thank you!
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Old 12th September 2013, 06:51 AM   #9
alayn91 is offline alayn91  France
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Hello,

Unfortunately, in post n1, I'm afraid T10 is useless, with its Vbe = 0V.
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Old 12th September 2013, 09:43 AM   #10
Gost22 is offline Gost22  Bolivia
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Quote:
Originally Posted by alayn91 View Post
Hello,

Unfortunately, in post n1, I'm afraid T10 is useless, with its Vbe = 0V.
That's it! is missing something, but what?
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