3 Transistor HP Amplifier with low dist

[avtech]

Very nice

 

[marin cornel]

professional.
good job!

 

[knauf1919]

Romanian:
Marin, da-mi adresa și îți trimit un set cadou. Vorbesc serios.
English:
Marin, give me your address and I'll send you a gift set. I'm serious.

 

[marin cornel]

Hello,
Thanks to knauf1919. I received the pcb from him, a gift as promised.

 

[marin cornel]

I finished assembling the components. Everything works very well. Thanks knauf1919 for pcb and lineup for sharing the project.
In the near future I will make a case worthy of this amplifier.

 

[knauf1919]

The best headphone amplifier. Glory to the one who designed it.

 

[weissi]

Love it. Thank you lineup and Knauf1919!

Edit: yes, BP output caps not needed... I had them laying around, not fitting any other application I have.

 

[jpk73]

The best headphone amplifier. Glory to the one who designed it.

Which circuit did you use finally? Could you please post the final schematics of the BJT version including the regulator section? I want to build it!

 

[knauf1919]

 

[knauf1919]

Power supply.


ERATTA!!!

 

[weissi]

Guess the divider on the silkscreen was then 80k / 100k

 

[knauf1919]

Hard to find 80K value.
30K + 150K looks more realistic.
I later edited the values.

 

[danielwritesbac2]

a couple of questions. . .

With the 5v version, is there enough headroom for 5x gain, if line level output? If not, the 12v is fine.

Is there a preamp schematic available, perhaps with a TO92, such as BC337 or 2n2222, instead of the BD139?

 

[Andersonix]

In the near future I will make a case worthy of this amplifier.

Hi Marin Cornel! I look forward to seeing your DIY case!
May I ask why you have labeled your input and output terminals on PS board as "250R"?
Cheers!

 

[marin cornel]

Hi Marin Cornel! I look forward to seeing your DIY case!
May I ask why you have labeled your input and output terminals on PS board as "250R"?
Cheers!

Hello,
This is how they were marked with 250R. I don't know where I got them from. It certainly meant something in the set-up for which they were intended. I didn't remove that mark.

 

[BucketInABucket]

This is a new, revised Version.
It has slightly better data and shows also LM317T for the 12V supply.
I think it should work with 32 Ohm and 250 Ohm, too.

Probably needs a change for 300 and 600 Ohms headphones.

Hey Lineup, what is the point of C6? Removing it doesn't seem to do anything in the sim...

 

[avtech]

I know I am rather late to the party but I would like to suggest a small improvement to this design. As it stands, its PSRR is quite poor simply because the first stage is biased directly from the supply. Any noise on the supply is fed straight to the input and care is needed with the PCB layout to ensure output stage signal currents do not induce voltages onto the supply feeding the bias resistors.

To fix this I would suggest using a decoupled potential divider for generating the required bias voltage and then feeding this to the base of the first transistor via a suitable value resistor.

Cheers

ian

See this post

 

[BucketInABucket]

Ahh, makes sense, I'd imagine a 10u X7R MLCC would probably be fine there?

 

[danielwritesbac2]

Here is the recommended version for 250ohm - 300ohm - 600ohm. . .

Can I have recommended version for 20k load and for 50k load, either with 6x gain and 12vdc supply?

Oh man, I've ever so much need of that!
I have so much amplifier projects that can't match up phone/pc/tablet commonplace sources, and therefore 3 transistor singleton-input single-rail preamplifier is hot on my wish list.

The other alternative is buy a better source, build another amplifier, repeat; but, unfortunately, that typical method doesn't result in fully-practical music outcome.

 

[widea]

Is there a brand and/or type of headphones that particularly matches with this amplifier? Or, to rephrase the question a bit: what headphones do you use with this amplifier?
Reason for asking: the sound in the right side of my headphones (Beyerdynamics DT770 Pro 80) is gone, have to look for a new pair and could use some suggestions, thanks.