Class A, 4 Watt, No Feedback, Simple Circuit, Great Sound

[U230421]

A beautiful 2-stage amplifier: a Sziklai front and a smart buffered buffer.
A dc feedback from output to R4 (RC) can improve temperature stability.

 

[adason]

I have not seen Lineup around the forums for some time now.

he is back!
3 Transistor HP Amplifier with low dist

 

[vizion]

Hi Guys, how many watts does this amp draw ? I was thinking of using batteries. Thanks.

 

[PRR]

Hi Guys, how many watts does this amp draw ? I was thinking of using batteries. Thanks.

Easily read-off from schematics in reply #54 or #56. 20V, 1.1 Amps, 22 Watts. For 4 Watts audio output. This is in the group of class-A amplifiers which only approach 25% efficiency.

This is a poor pick for battery power.

 

[joensd]

Another rainy day and still no vaccine shot in sight.
What else to do than making another PCB-layout of lineup´s super simple, single-ended class-A BJT designs.
So next PCB order is lineup´s headphone amp and this cute little class-A amp.

 

[OldDIY]

#32 You can do without the first two transistors.
It will look like a Philips circuit from the 70s.
In the emitter Q3 at the output, include 1.8 kΩ. From emitter to ground 270 ohms. The operating point is set by the divider on the base Q3.

 

[joensd]

Order a batch of 5 for myself but I can let go of up to 3 PCBs for 2.50$ plus shipping.

 

[xrk971]

Nice work there, Joensd!
Love it!

It would make a nice headphone amp for HE6i cans.

 

[joensd]

Nice work there, Joensd!

Thanks X!
The circuit is simple enough which was the attraction/beauty for me.
I have to admit that despite the Passlabs&Class-A craze around here I still haven´t properly made anything class-A so that will be my first!
It really looks good on paper and can be done with parts from the drawer.

My Sennheiser HD598 is much more modest than the HE6i so I´ll use another of lineup´s designs hopefully pretty soon:
3 Transistor HP Amplifier with low dist
Really excited to see how a single-ended class-a design compares to all the headphone amps I built over the years.

The 4W class-A amp will eventually power my Mark Audio A7.3 in an active setup so power needs are pretty low to get sufficiently loud.

 

[ernesternest]

Order a batch of 5 for myself but I can let go of up to 3 PCBs for 2.50$ plus shipping.

Hi Jens, count me in for a pair pls. Cheers, Ernst

 

[joensd]

Hi Jens, count me in for a pair pls. Cheers, Ernst

Hallo Ernst,
unfortunately the 3 leftover PCBs are already spoken for but as I have other projects in line before this one I might you give you my pair.
Worst case: I can order another batch at a later point.
Let me think about this for a while.

 

[ernesternest]

Jens, I do have a lot of projects as well. Pls. keep it - it was just out of curiousity. Maybe later at some time. Cheers, Ernst

 

[prasi]

my Diy pcb etching version.

 

[joensd]

Very nice and clean layout (as per usual) Prasi!
C4 looks a little on the small side. What type/diameter is that?
I personally would use a 25V type at least which start at about 16mm diameter.
(at my distributor)

 

[thimios]

my Diy pcb etching version.

We are lucky that we have you here my friend!

 

[prasi]

Hello Joen, Thanks. its indeed 16 mm dia. and the other one is 13 mm dia
Hi Thimios, thanks.:

 

[prasi]

same size pcb with side mounting option for slim cases. 18mm dia cap.
5mm to 22.5mm pitch input coupling cap

 

[Cambe]

 

[prasi]

hmm, I wonder who told me to work on the design for slim cases

 

[prasi]

Lineup, you should consider moving your thread to someplace else, here in solid state, you will find only bass heads who want min 100W power.