Audio amplifier with 2n3005

[selim]

Hi Gost22,

Here is the circuit of the Elektor Amp.My mods are:

1.The outputs are complimentary, using both NPN and PNP power transistors.

2.The supplies to the early stages are RC filtered

3.Emitter degenaration is provided for the input stage

4.Some capacitor mods

I'll provide the PCB photos as soon as I get them.Basically, one PCB contains
2 channels and the power supply, together with provision to house the
output transistors on L brackets on the PCB.Quite compact and neat, I
believe.

Cheers

Selim

 

[selim]

Here are the PCB pictures.

Cheers

Selim

 

[Samuel Jayaraj]

Let me show you another diagram audio amplifier that works very well. Can be adapted to work with complementary output transistors.

Circuit you posted looks very interesting. Do the BD139/140, 235/236 transistors need to be mounted on their own heatsinks/main heatsink? Is a single pair of 3055s sufficient for 4 ohm loads?

Any description about the sound quality?

Thanks for posting!

 

[donpetru]

@Samuel Jayaraj, schematic audio amplifier which I previously posted is pretty old (80's). For example, to have optimum performance on 4 Ohms at the supply voltage, is much better to install two pairs of transistors. Then, BD235 and BD236 can replace with MJE15030/15031. These transistors can be attached to the main heatsink.
On the other hand, is much better BD139/BD140 have its own heatsink.

 

[selim]

Hi Donpetru,

I believe the base of T16 in your circuit (the lower 2N3055) should be
connected to the collector of T14 (BD236).As shown in your post, the
amplifier is not working.

As you have pointed out, the driver pair (BD235 & BD236) should better
be replaced with other transistors up to the task.At the supply voltages
shown, they won't live long.The output transistors, too, will have a hard time
surviving at these supply levels.

Other than these minor points, I believe your amp to be a fine sounding
one.

Cheers

Selim

 

[donpetru]

@selim, you're right, I rushed and I attached the wrong version of the audio amplifier. Sorry!
I attached below the correct amplifier diagram published in the journal Tehnium and several specialized books in Romania, in the '80s.

Please, a moderator to delete circuit diagram which I attach it in post #20. Thanks.

 

[RSK]

Selim was very kind to help me with the boards. Here is my final build of his modified circuit. DC offset is stable at 1.1mV and 4.5mV.
Coming up in a few days, its listening test.