Hi! Did anyone tried this kit? It is a cheap quasi complementary class AB amplifier from China with tone controls. With some build in problems, which you must solve by yourself. There is no or bad quiescent current supply which results in bad cross over distortions. I came up with a transistor as adjustable Zener diode for the bias voltage, which I attached to a finger of the heat sinks, this works so far good,
since 2 years I have this amp in use for my 2 channel TV audio. And I used 4 old 2n3055, and not the shipped transistors which came in the kit.
I mean, it is something from which you can learn a little about amp circuit design. If you be successful, the result is better than expected for such a kit.
And, I think you can not buy such an old amplifier design in a new product today.
Armin
since 2 years I have this amp in use for my 2 channel TV audio. And I used 4 old 2n3055, and not the shipped transistors which came in the kit.
I mean, it is something from which you can learn a little about amp circuit design. If you be successful, the result is better than expected for such a kit.
And, I think you can not buy such an old amplifier design in a new product today.
Armin
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If there is no bias then its a class B amplifier.
Those heatsink dont look like they will take a lot of power.
Those heatsink dont look like they will take a lot of power.
a class B amplifier also needs bias, if there is no bias, or to less bias, crossover distortions appear. This x850 kit had to less bias, even for class B. True, for a real class AB amp the heatsinks are to small.
I have seen similar designs.
Using over sized output devices for simple 6 to 10 watt amplifiers.
Its why the small heatsinks work.
Other than that, from the values at a quick glance.
DC offset would be very high. And what little bias there is, would mainly be on the positive output rail device. around 1 to 3 ma of idle current
The second gain stage could at least use a boot strap, and a basic zener for the input pair.
Being Quasi Output, Baxandall diode would help as well.
As is, most the current for output comes from the positive side output transistor.
Around 1 amp for 8 to 12 watts.
People like to make fun of the Velleman K8060
Compared to this. it is very very advanced LOL
Using over sized output devices for simple 6 to 10 watt amplifiers.
Its why the small heatsinks work.
Other than that, from the values at a quick glance.
DC offset would be very high. And what little bias there is, would mainly be on the positive output rail device. around 1 to 3 ma of idle current
The second gain stage could at least use a boot strap, and a basic zener for the input pair.
Being Quasi Output, Baxandall diode would help as well.
As is, most the current for output comes from the positive side output transistor.
Around 1 amp for 8 to 12 watts.
People like to make fun of the Velleman K8060
Compared to this. it is very very advanced LOL
as I wrote, I use a transistor to generate a proper bias voltage, and attached it to a finger of a heat sink for temperature compensation.
Then I watched the sine output signal with a oscilloscope for full crossover distortion elimination, and then I give a little more bias, but not so much that the heat sinks get to warm. This transistor replaces the 2 diodes.
Then I watched the sine output signal with a oscilloscope for full crossover distortion elimination, and then I give a little more bias, but not so much that the heat sinks get to warm. This transistor replaces the 2 diodes.
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I have built the power amp only version of this and yes it has many shortcomings but having said that its a good training aid !
teaches students how to solder
what bias is what offset is and bootstrapping etc all in all a cheap learning aid
Trev
teaches students how to solder
what bias is what offset is and bootstrapping etc all in all a cheap learning aid
Trev