F6 amp with SemiSouth SJEP120R100

[Gyuri]

Accident was entirely my fault..
IRFPs has shorter legs, although screw was secured, but it wasn't connected to source leg.

It is now settled down at 1.82A, with minimal drift.
DC offset changing between -15 +10mV as amplifier is playing.

It has a marveolus sound.
I didn't play with 10Ohm pots yet.
If one hasn't have SemiSouth parts, regardles of it, it is a must have to build piece.
And you do not have to constantly scared, what if...

 

[2 picoDumbs]

Nice work mate. Congratulations.

Here's a song to celebrate

https://www.youtube.com/watch?v=9SXWX6qg0y4

 

[Gyuri]

Thanks guys,
I'm just wondering, I will disassemble J2, and will put it in its case.
Perhaps I will reorder F6 kit, and I will build another one.
Or I leave J2 as is, and order two F6 kits, and will build a double balanced MOSFET F6, similar to my ZV9:
http://www.diyaudio.com/forums/pass-labs/164003-so-my-quad-zv9.html
Of course it needs some money.
Now there isn't enough heat sinks and aluminium sheets and bars and so on.
And I have too much plans.

 

[Gyuri]

Unwittingly, I developed the amplifier, which needed for preheating, to reach proper quiescent current. It can be done with heat gun.

 

[Gyuri]

I should build in SemiSouth fets.
Before it I would like to make some measurements with IRFP250s.
Though I just listen to it rather.

 

[Gyuri]

About pots:
I haven't done too much.
I have took a short experiment with wipers towards source pins.
I didn't like it.
As if it has lost its sweetness.
So there is now, as can be seen this schematic:

 

[Gyuri]

I have repeated the above experiment.
The result is the same.
It is a little rough, that I do not like the opposite settings of the wipers.
But I think it losts the sweetness in some extent.
I think it is the greatest toy what we ever got from Papa.
Many thanks for it!

 

[2 picoDumbs]

Also try adjusting one pot independently of the other.

 

[Gyuri]

Yes, there are several possibilities.

 

[Gyuri]

Then I try to do distortion measurements,
and see if there is any correlation between the popular and less popular sound pictures!

 

[2 picoDumbs]

Would you be willing to do an experiment on my behalf?

Start with both pot wipers at source pin.

Assuming your pot is a single turn pot, then turn pot on bottom mosfet 1/4 of a turn, so it looks like this.

You may as well repeat the same experiment for the top mosfet..

 

[2 picoDumbs]

Start there then just keep turning till something sounds good.
Then tell us what values you have across pot and wiper.

 

[Gyuri]

I will do my best for sure.
But I must have to bring it to a most usable and less dangerous state before.
You know, my cat runs through it.

 

[nashbap]

I do the same. Widening the mosfet holes is no issue either. Just use a drill bit at high speed, in reverse, and you avoiding any chipping that sometimes occurs when drilling the standard way.

That's a good tip. So is the one about bias testing without the Mosfets.

Thanks. Nash

 

[Gyuri]

Some of my Pass amplifiers works in peaceful agreement:

 

[Gyuri]

I'm just getting tired in role adjuster of automatic offset and quiescent current.
It is a half day long activity.
So I will make some measurements, then SemiSouths gets in place.
Regarding pots, there is no other settings for me, just wipers at source pins.
Though there was some other thing, what I have done:
http://www.diyaudio.com/forums/digital-line-level/284396-msb-platinum-link-2.html
It also has effect on soundscape, there is good and less good.
More precise and holografic sound, better controlled bass, it is good.
But sweetness is lesser now.
They say about MSB Platinum Link DAC:
"At least 100 hours of burn-in is required on this DAC. Customers generally recommend
one month."
There is hope, which has die only finally.

 

[Gyuri]

I have made some measurements.
According to these, it sems to be I'm only half deaf yet.
Be prepared, more to come!

 

[Gyuri]

Sweetness is back!
SemiSouth JFETs are in place..
They sings me, like angels in heaven, for greater glory of Pass and SemiSouth.
If we can be considered Steve Strauss as an angel.
But why not?
http://www.stockfisch-records.de/mp3s/StStrs_oldcrow_hi.mp3
Buzz is right.
It is my favourite Pass amp.
Many thanks to Papa, and Mike!

 

[buzzforb]

HeHe. I thought you would like it. Where did you end up on the resistors values?

 

[Gyuri]

As in first post schematic, 0.1 Ohm.
It was just hysterical with IRFP250.
This is quickly reaches stability now.