amp

dell · 29th December 2007, 02:07 AM

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.

Jeb-D. · 29th December 2007, 03:42 AM

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.

dell · 6th January 2008, 12:45 AM

schem attached. thanks for any help, in advance

AndrewT · 6th January 2008, 11:45 AM

post a schematic of the power supply.
include mains input right through to power amp connections.

dell · 7th January 2008, 09:52 AM

attached here is the schematic diagram of power supply.

AndrewT · 7th January 2008, 09:57 AM

I've refreshed 10 times and waited 4 minutes.
Dell,
did you forget to check read your post?

longthrow · 7th January 2008, 10:23 AM

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this circuit should not be published..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.

destroyer X · 7th January 2008, 09:46 PM

Also very old schematic, from 1970 i think.

regards,

Carlos

destroyer X · 7th January 2008, 09:49 PM

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

destroyer X · 7th January 2008, 09:52 PM

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

29th December 2007, 02:07 AM	#1
dell diyAudio Member Join Date: Nov 2005	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.

6th January 2008, 11:45 AM	#4
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	post a schematic of the power supply. include mains input right through to power amp connections. __________________ regards Andrew T.

7th January 2008, 09:57 AM	#6
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	I've refreshed 10 times and waited 4 minutes. Dell, did you forget to check read your post? __________________ regards Andrew T.

7th January 2008, 10:23 AM	#7
longthrow diyAudio Member Join Date: Aug 2007 Location: cebu phils	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. __________________ H V E Audio

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29th December 2007, 03:42 AM	#2
Jeb-D. diyAudio Member Join Date: Nov 2005 Location: SoCal	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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