6W, Class A, hopefully something I can build. :D

[h_a]

Emitter resistors are necessary in the real world as they help in current sharing between paralleled transistors - remember real parts are not perfectly equal in their parameters (especially beta or VGS) 😉 This is one of the points not seen in simulation.

Another point is that simulation regularly predicts unrealistic results. That's due to insufficient models and often also due to incorrect simulation. Just simulate a known amp (where you have all specs and plots) and compare. You will be surprised.

In any case, at these low levels of THD also construction details as pcb-layout, wiring, position of the toroid and more become decisive wether you reach your goal or not.

Do not keep your eye so close to the simulator, build and measure the beast. 😀

Have fun, Hannes

PS: if you want real fun, measure THD while moving the wiring in the amp.

 

[keantoken]

Fotios, I never thanked you properly for your help on the transformers. Thanks, Fotios. 🙂

Emitter resistors are necessary in the real world as they help in current sharing between paralleled transistors - remember real parts are not perfectly equal in their parameters (especially beta or VGS) 😉 This is one of the points not seen in simulation.

Another point is that simulation regularly predicts unrealistic results. That's due to insufficient models and often also due to incorrect simulation. Just simulate a known amp (where you have all specs and plots) and compare. You will be surprised.

In any case, at these low levels of THD also construction details as pcb-layout, wiring, position of the toroid and more become decisive wether you reach your goal or not.

Do not keep your eye so close to the simulator, build and measure the beast. 😀

Have fun, Hannes

PS: if you want real fun, measure THD while moving the wiring in the amp.

Well, I got some small heatsinks out of the monitor and will breadboard a small prototype in a minute with no parallel outputs. Let's hope the smoke stays inside. 😀

- keantoken

 

[keantoken]

Is there something wrong with my MJE340/350s?

There isn't a metal pad on the back. Just plastic.

😕

- keantoken

 

[MJL21193]

There isn't a metal pad on the back. Just plastic.

Most TO-126 are like this. In my opinion, a benefit - no isolation washer needed, just grease it up an' bolt it on.

 

[Lumba Ogir]

Hannes,
the quality of your contribution has unexpectedly risen lately. Have you maybe taken an evening class?
😀

 

[ostripper]

By MJL - There isn't a metal pad on the back. Just plastic

That is strange.. old 340's and even old c3503's HAVE metal
on the backs of the devices, but the new MJE/KSA to-126's
are all plastic.

Once I found this out I realized you could mount them
"backwards" for PCB layouts,etc . No mica required either😎 .
OS

 

[lineup]

I am struggling with this Single End MOSFET Class A.
It is kinda ZEN but uses one current source at 1 Ampere.
Output devices are N-Channel.

Only four transistors: 2 x 2N5401 and 2 x Exicon ECF20N20
Think two Exicon ECF10N20 will work just as well.

At 18 VDC, 1 Ampere = 18 Watt,
it can produce 2, maybe 2.5 Watt RMS with acceptable dist.
Mainly 2nd and 3rd harmonics. The higher orders will fall off nicely.

It is not 🙂 easy to balance gain, bias and operation voltage
to make this amplifier optimal.
But it is a nice project and fairly low idle powers.

Lineup

 

[h_a]

Hi Lumba,

not that I'm aware of 😱

Especially my last post was plain general info that everybody also finds with a little search here on the forum.

But I think you just refer to my putting down of SPICE; I think you maybe misunderstand me here. SPICE is a perfectly nice tool for evaluating amps, but it has it's limits. If you seriously go for anything less than 0.05% THD I would not trust SPICE. The models are - in my experience - much too limited in quality.*

Of course one can improve them (andy_c did that), but everybody who is able to do that also knows the above.

Have fun, Hannes

*real pros excluded.

 

[Lumba Ogir]

Hannes,
answering late a previous question, please check this book:
Hartmann, William M.
Signals, sound and sensation.

 

[h_a]

Hi Lumba,

thanks for the reference - I'm lucky our library has it. Let's have a look.

Have fun, Hannes

 

[keantoken]

I am struggling with this Single End MOSFET Class A.
It is kinda ZEN but uses one current source at 1 Ampere.
Output devices are N-Channel.

Only four transistors: 2 x 2N5401 and 2 x Exicon ECF20N20
Think two Exicon ECF10N20 will work just as well.

At 18 VDC, 1 Ampere = 18 Watt,
it can produce 2, maybe 2.5 Watt RMS with acceptable dist.
Mainly 2nd and 3rd harmonics. The higher orders will fall off nicely.

It is not 🙂 easy to balance gain, bias and operation voltage
to make this amplifier optimal.
But it is a nice project and fairly low idle powers.

Lineup

Interesting circuit. I've never messed with MOSFETs. It looks like the current mirror could easily be turned into a push-pull configuration a la Doug Self.

An externally hosted image should be here but it was not working when we last tested it.

EDIT: OMFG... The image is larger than I thought...

- keantoken

 

[U102324]

It is not 🙂 easy to balance gain, bias and operation voltage
to make this amplifier optimal.
But it is a nice project and fairly low idle powers.

Lineup

Play with this idea.




Nico

 

[keantoken]

I would, but I don't have any MOSFETs and no money to order them. Maybe later.

I got the output stage (for my amp) set up on breadboard, but something's wrong. Output sticks to one rail.

- keantoken

 

[keantoken]

Okay, I finally have the output stage working. Didn't have much time to work on it, but he output stage is working now.

Attached file is the components I used.

The circuit oscillates if I attach anything between the emitter of Q3 and Q4.

I will go ahead and build the input and feedback parts of the circuit to see if I can get it so I can listen to it.

- keantoken

 

[keantoken]

Here's file.

- keantoken

 

[lineup]

Interesting circuit. I've never messed with MOSFETs. It looks like the current mirror could easily be turned into a push-pull configuration a la Doug Self.
http://www.dself.dsl.pipex.com/ampins/discrete/cfp3.gif
- keantoken

I know about that circuit from D.Self site.
It is something between one CCS loaded output stage and Push-Pull.

It is a possible way to increase the power output.
However, I think it will make less PSRR.
CCS has got very good power supply rejection ratio. This is why I prefer this.

Nico Ras circuit looks very good.
But same here. The PSRR will suffer a bit

Regards

 

[lineup]

Here's file.
- keantoken

http://www.diyaudio.com/forums/attachment.php?postid=1731211&stamp=1233473601

That output stage is something to explore further.

I must say you are good, keantoken 😎
I love members that have the ability to think Out of The Box 🙂
And you are certainly a creative person, mate.
Like Nico Ras, too ....

Lineup Regards

 

[keantoken]

Thank you Lineup!

I must get to bed soon... I was quite surprised actually when you replied Lineup. In my country it is 2 hours past midnight! 😀

- keantoken

 

[lineup]

Here at my place it is 9 in the morning, Sunday Morning

Johnny Cash - Sunday Morning Coming Down

On a Sunday morning sidewalk,
I'm wishing, Lord, that I was stoned.
'Cause there's something in a Sunday
That makes a body feel alone.

 

[AndrewT]

Q5 & Q6 are operating Iq~1.3mA that seems very low for 340/350 transistors.

I do believe that the two bias controlling transistors cannot work. I reckon that as soon as an emitter current changes, the transistor pair send corrections to the outputs and that your oscillation.