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Old 29th December 2007, 02:07 AM   #1
dell is offline dell  Philippines
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Unhappy amp

confused: hi there, i want some help. Any body please tell what would be the problem the amp I made. I notice the speaker seems like breathing, moving back and forth in very slow frequency, maybe 0.5 - 1 cycle per second. Can this be called as low frequency oscillation? The sound reproduced is quite good (base on my senses only), no signs of overheating what bothers me is the thing i mentioned aboved. The topology is quasi-complementary bridge amplifier using cheap transistors 2n3055.The input is a simple ce amp with phase splitter and phase inverter to drive its partner amp, followed by two voltage amp then next are the drivers for the final amp which operate in bridge classB. I need some help not only solved this problem but also to gain knowledge.
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Old 29th December 2007, 03:42 AM   #2
Jeb-D. is offline Jeb-D.  United States
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Yes, Low frequency oscillation or instability. It is common when you have multiple stages sharing a power supply that has high impedance. Basically it's positive feedback on/through the power supply rail, at frequencies that the filtering cap becomes in-effective. Post a schematic and we can help.
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Old 6th January 2008, 12:45 AM   #3
dell is offline dell  Philippines
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Smile amp problem

schem attached. thanks for any help, in advance
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File Type: jpg schematic.jpg (62.3 KB, 586 views)
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Old 6th January 2008, 11:45 AM   #4
AndrewT is online now AndrewT  Scotland
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post a schematic of the power supply.
include mains input right through to power amp connections.
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Old 7th January 2008, 09:52 AM   #5
dell is offline dell  Philippines
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Default power supply

attached here is the schematic diagram of power supply.
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Old 7th January 2008, 09:57 AM   #6
AndrewT is online now AndrewT  Scotland
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I've refreshed 10 times and waited 4 minutes.
Dell,
did you forget to check read your post?
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Old 7th January 2008, 10:23 AM   #7
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Default thunder amp

thats a "thunder power amp" very popular in phils. ,a bridged amp
having a single supply (0-50V).

the circuit claims 500-1Kw having only 8 primitive trannies (2n3055)..i wonder hows that possible!!! obviously overrated!

this circuit should not be published..
very unstable..vas is tip35a,phase splitter is c945...high THD & no zobel net.
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Old 7th January 2008, 09:46 PM   #8
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Default This one works Dell..... but only 250 Watts


Also very old schematic, from 1970 i think.

regards,

Carlos
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File Type: jpg this one really works.jpg (81.5 KB, 348 views)
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Old 7th January 2008, 09:49 PM   #9
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Default Using BC556 into the input, BD139 as VAS


BD139 and BD140 as drivers and using any power NPN to substitute the 2N3055 (as modern ones have better specifications) you will be happy.

This thing works!

here is he upper half amplifier, it is bridged.... the lower amplifier i will attach schematic has a phase inverter into the input.

regards,

Carlos
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File Type: pdf this one works.pdf (37.9 KB, 87 views)
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Old 7th January 2008, 09:52 PM   #10
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Default This schematic was published by Phillips do Brasil

Into 1970.

Here is, attached, better image of the lower half.

This one works!.... if you like bridge ones, using those standard transistors, old style of amplifiers, this will fit your needs.

regards,

Carlos
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File Type: pdf the phase inverter.pdf (48.4 KB, 58 views)
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