10 Watt Single End, JFET input - Lateral N-MOSFET output

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Hi Gabor,

you are not correct by your assumption what I say.

Several comments here claims that direct coupling is better than capacitive coupling, or rather single supply is not as good as split supply.

I am merely pointing out that whether using split or single supply, the signal path to the load is effectively capacitive coupled.

What line-up pointed out without saying is that the loudspeaker coupling capacitor and supply capacitor size need to be considered for LF response as they are in effect in series every other half cycle.

Nico
 

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Hello Nico
Here is the schematic I talking about .
There are another schematic in these tread so be carefull do not be confused .
On the PC board that is coupling capacitor .
That is how the schematic was design , and even AKSA wrote that is a great design .
So I just want to check it out .
Regards
 

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Hi Gabor,

there is nothing wrong with the design, it is very nice.

I was commenting on the fact that Umut preferred a split supply with no coupling cap, and my comment was that the speaker is in fact always decoupled by a capacitor, whether it is a single supply or split transformer supply.

I have no problem with the widow maker, in fact I think it is a very neat design.

Kind regards

Nico
 
00940 said:
But does the quality of the caps matter in the same way (output coupling cap vs psu caps) ? From the posts by Jan Didden in that thread : http://www.diyaudio.com/forums/showthread.php?s=&threadid=137497&pagenumber=2 , I'd think not.

But I might be confused. :dead:

You are not confused and Jan is absolutely right. The power supply cap is as much part of the signal path as is the output transistors feeding the loudspeaker.

It is very important to by-pass large caps with little ones to maintain linearity and phase over a the entire audio band.

Nico
 
Nico Ras said:
You are not confused and Jan is absolutely right. The power supply cap is as much part of the signal path as is the output transistors feeding the loudspeaker.

Nico

Quoting Jan Didden: "The audio return current from the speaker does indeed pass through the supply cap. But that does not impact the audio *signal* at the amp output.

Look at it this way. If we have a cap that distorts 10%, and if it is true that it is 'part of the signal', how could we then ever build amps with 0.001% distortion."


Reading this, I've got trouble understanding how the power supply is in the signal path "as much as the output transistors". From what I understood, the output cap of an amp with single supply will add distortion, not so much the PSU caps in a split supply :xeye: (it's the post 39 of the above mentionned thread)
 
00940 said:


Quoting Jan Didden: "The audio return current from the speaker does indeed pass through the supply cap. But that does not impact the audio *signal* at the amp output.

Look at it this way. If we have a cap that distorts 10%, and if it is true that it is 'part of the signal', how could we then ever build amps with 0.001% distortion."


Reading this, I've got trouble understanding how the power supply is in the signal path "as much as the output transistors". From what I understood, the output cap of an amp with single supply will add distortion, not so much the PSU caps in a split supply :xeye: (it's the post 39 of the above mentionned thread)

Why would your capacitor add distortion, this must then be true for your input decoupling as well as your feed back decoupling?
 
Hello Nico
I miss understood your comment .
Sorry about that .
Yes I use a large cap on the output , a small one and a teflon capacitor .
I don't understand why would the coupling capacitor ad 10% distortion . You right Nico it would be the same on the input capacitor case if we talk about real distortion .
There are many similar design and they sound well some of them incredible .
Even Mr Pass has the Folks amp with 20 000uF coupling capacitor in the amp ad he said it sound great .
Greetings
 
00940,
"The audio return current from the speaker does indeed pass through the supply cap. But that does not impact the audio *signal* at the amp output.
No wonder you get confused by such an inconsistent statement, Jan would have extreme difficulty explaining that.
Look at it this way. If we have a cap that distorts 10%, and if it is true that it is 'part of the signal', how could we then ever build amps with 0.001% distortion."
Jan`s software ignores completely the distortion caused by capacitors, like most other distortions. The only distortion taken into account is the irrelevant THD.
From what I understood, the output cap of an amp with single supply will add distortion, not so much the PSU caps in a split supply
Both will equally add distortion.
 
Hello
I almost finished populating the PC board the amplifier posted by lineup and design by Widow maker.
Hopeful I can test at the next week some times .
I only need the 1000uF capacitor , after I can ad the Power supply . I ad two capacitor for the power supply on the PC board .
I built several Class A amplifier like Sewa , both Hiraga , some Alephs like Aleph 30 , X , Aleph 2(not finished)but because these SE and so SIMPLE I can hardly Wait to test it .
I hope it does sound good how even AKSA wrote about .
Thanks to line up and Widow maker for the design and for sharing the schematic .
I post a picture from the PC board .
 

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Hello
I hate the soud of the dry tantalum capacitors .
I use Philips auxial which is one of the best capacitor in the market and a small Russian teflon capacitors .
I did tested many capacitors in the SEWA output , nothing come close to the Philips auxial .
I did tested tantalum capacitors in the input in a couple amp but Black Gate N one of the best capacitor.
I do not use tantalum caps , probably I would use resistors from Audio N but no capacitors .
Do not forget Mr. Pass use in the Folks amp 22 000uF capling capacitor .
And he wrote it sound great !
Thanks for the advise .
Regards
 
Hey Widowmaker,

The 6,2k drainresistors seems to load the 2SK246 very hard giving unnecessary high THD. Did some sims to see if it could be bettered.

With ca 110V and 22k the distortion is reduced 10x! Had to change the 1,5k sourceresistor to 1,3k to get as symmetric clipping as possible with ca 18V at the output device gate.

With the results I get one almost wonders if there is something wrong with the jfet models we are using? At 1W/8ohm I get 1% THD mostly 2nd order.

Have you done any IRL measurements?

These are the circuits I simmed:
 

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widowmaker said:
I have one new version of solid state SE AMP:
Some features:
Zero feedback
Thermostabilization of output offset through negative supply for source of input JFET transistor.
Schematic:


Is there a problem with the original circuits DC-stability? When AC-coupled output, I would think it would be a minor problem with some drift?
 
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