simplest amplifier possible with BJT's?

[boxedin]

Rudy,

Did you find any design yet ? let me know if you find any or satisfied with circuit. Can you also show thepicture of your AR3 rudistar head phone amplifier you made?.

I may try to do that as my first project.

Let me know.

Thanks
Alexk
toronto

[lineup]

Great!
Another free Nelson Pass amplifier.

Difficult to build?
I wouldnt think so

Originally posted by Nelson Pass
I do like a challenge.

Select both devices for high beta. I assumed 50
on the power device, and 100 on the driver.

[rmgvs]

Boxed in:

here is the latest version of the prototype of the simplest amplifier. It still is built around the AR-3 circuit. The real headphone amp is smaller in physical size, I have no picture at hand, but will post it as soon as I have that available.

[boxedin]

hi rudy,

I do not see 2n3055. Did you use any other transistor?. Do you now what is the latest equivalent of BC109 and 2n3055?.

i Can't find them. Let me know.

How much the output wattage ? 1 W?. And also what is your powupply rating ? 30 v 1A?

And also how many 2n3055 we can add second stage? WIll the sound quality go bad if we addd more transistors in second stage?.

Let me know.

Thanks
Alexk

[boxedin]

Here is the picture of the my simulation.

I get only 11 mA Ac signal (Peak to peak) going through 8 ohms.

But DC current through 330 ohm resistors is 500 MA dc current. Ca we convert this to AC current somehow?.

Let me know.

Thanks
Alexk.

[rmgvs]

I use 2n3055 and it is fitted on the heatsinks on both sides of the chassis. I use around 25V and 1 Amps. The (power) resistor belonging to the output 3055 has been changed to 6,8 Ohms (25 Watts, also fitted on the heat sinks). The driver transistor was in the original AR3 (if I remember correctly) also a 3055 but can be changed to any other same type smaller power transistor (BD type for example). No transistor in this circuit is critical, you can try anything as long as the power rating of the 'end' transistor is big enough and can stand 1 Amp easily. Sorry not to be more precise but I don't have the complete history of building this thing at hand, in the mean time somebody else is playing with it. Output power is around a meagre 1 Watt at 8 Ohms, but enough for a lot of listening.

[boxedin]

DID you make any new class A amplifier only with BJT ?

As far as Transistor replacing 2n3055 are 2n3772,2n5886 and MJ21294G. Hope i can improve the output power. Which one is power resistor in this circuit ?. 3 parallel 330 Ohm? SHould i change that to another value?.

Let me know
Thanks
Alexk

[rmgvs]

I did try several variants of the amps in this same cabinet at the time of the beginning of the discussion on this topic. If you want more power with the basis set-up of the AR-3 using 8 Ohms speakers you have to change the 330/330/330 resistors to one big resistor of 6,8 Ohms (or 8,2 Ohms). At the time no circuit could give more than around 1 watts using the same minimum amount of components and the given design criteria, which the reason why I gave up at the time. The new circuit of last week looks promising, I am very curious about the specifications and listening test from builders...

[boxedin]

hi,

what is last week circuit ? which thread?.

Thanks
Alexk

[lineup]

Originally posted by boxedin
hi,

what is last week circuit ? which thread?.

Thanks
Alexk

This is my pricinpal suggestion for a simple and good amplifier.
Works in Class A.
The gain in the voltage amp stage, Q1+Q2, is set by (R2/R1) + 1

Output, voltage across R8 at Q3 emitter should be half supply voltage.
R8 should be same as impedance of load, or smaller.
For better efficiency ( more power output )
R8 should be replaced by a constant current source.

With higher currents and power transistors this makes a good Class A headphone amplifier / low power amp.

With only small signal transistors and lower currents
it makes a good preamplifier.