Humble Two. 15 Watt Class A. JFET input IRF540/9540 output.

[lineup]

Here I will publish a new amplifier.
It is called Humble Two.
It will output 15 Watt Class A in both 4 and 8 Ohm.
With low distortion.

I publish the simplified diagram now.
I will be back with more details later.

 

[lineup]

As you can see there is some gain in the output.
Actually it is x2.4.
Because of this the dropout is very low.
The output voltage is like max 15.62V of the supply which is being 16.0V.

 

[jacques antoine]

Neat! But LSK489 is hard to find.

 

[EUVL]

Just use 2SK209.

Has it been built ?
How is thermal drift being controlled / compensated ?


Patrick

 

[jacques antoine]

Just use 2SK209.

2SK209-LSK489: single vs. pair.

 

[EUVL]

What's the problem of buying a bunch and match a pair or two ?


Patrick

 

[lineup]

I intend not to build it.
But would be pleased if somebody would do it.

Transformer should be 2x12VAC.
For now you can seee how it looks. See first image.
Fourier Analysis shows THD is very low.
When I added two pole comp it was lower and ended at 0.000064%.

The second image shows the frequency curve in AC Analysis.

I will continue work and see if I can improve it.

 

[jacques antoine]

What's the problem of buying a bunch and match a pair or two ?

Nah, SST404. Still have some lying around.

 

[EUVL]

20nV/sqrtHz ?
Not for me.


Patrick

 

[jacques antoine]

20nV/sqrtHz ?

LSK489: 1.8nV/sqrtHz.
SST404: <10nV/sqrtHz
Picky? I am sure your ears can tell the difference 😉

 

[EUVL]

Yes, can tell also between J113 and 2SK209.
As said, not for me.


Patrick

 

[jacques antoine]

I agree, I commonly use J113 as CCS but never in the signal path, why would you?

 

[lineup]

I will check in 2SK209, if I have a SPICE Model.
Of course we do not need to have LSK489. Other JFETs can be good too.
----
I have 2SK209 in SPICE.
The model has IDSS 3.29mA
So I will use 3mA bias.

 

[jacques antoine]

Lineup - are U13 U15 to be mounted on the heathsink?

 

[jacques antoine]

The model has IDSS 3.29mA
So I will use 3mA bias.

Great, it should work for SST404 as well 👍

 

[lineup]

It is possible to use 2SK246, too.

 

[EUVL]

2SK246 = 2SK209.

2SK246 is obsolete.
2SK209 can still be had from Mouser, Digikey, ...., when not out of stock.
And noise is < 2nV/sqrtHz, actualy measurement.


Patrick

 

[jacques antoine]

Those obsessed with low noise may want to test the newer TI models:
JFE150 (single N JFET)
JFE2140 (dual N JFET)

 

[PMA]

Any sample built and measurements to show, @lineup ?

 

[lineup]

Here is the 2SK246 version.
THD is still 0.00006%