JFET input, MOSFET VAS, LATERAL output = Perfect!!

[GregH2]

swordfishy
Change one thing at the time, makes it easier to see what is an effect.
If you change several things, how do you know what did effect a change in sound?
You have to guess.

lineup, please see my comments in post #619

 

[mikelm]

Yes, Wahab, it does matter..... but God knows why

I worked in air cleaning for the last nine years and there may be an analogy that helps to explain this.

When attempting to remove a smell from the air - let's say the smell burnt toast. We can use carbon filters to reduce the volatiles and other filters to remove smoke particles BUT, even when these are reduced to an extreme small fraction of their original level the extremely sensitive human nose can still clearly identify smell the burnt toast.

It is accepted practice in the industry that as well as removing as much of the source of the unpleasant smell as possible it is also necessary to add a new pleasant smelling element to mask the remnants of the unpleasant odour.

Does this ring any bells ?

Perhaps it is impossible to have an amp with zero higher order content so we have to make sure there is enough low order HD to mask the remnants of the higher order harmonics - which are effectively low level noise.

Sounds feasible to me.

 

[lineup]

lineup, please see my comments in post #619

swordfishy
I am sorry.
Should have read your reply.

 

[GregH2]

swordfishy
I am sorry.
Should have read your reply.

No need to apologise lineup, I know you always have the best intentions and mean well towards other forum contributors.

And, you are right...I probably should spend more time listening than I have.

 

[lineup]

Recommended Fetzilla

If I was to recommend one version
to somebody who wanted to build a good Fetzilla
it would now be the circuit below.

It should be stable and sound good.
H2 second harmonic is dominant, follow by H3
Should not need any compensation cap.

I would be pleased to see someone try it out.

 

[mikelm]

I might build something like this but I would take extra measures to ensure that no neg rail PSU noise crept up to the i/p device - perhaps an RCRC filter which left me -10V for the i/p stage current source.

 

[sandyhooker]

??????

If I was to recommend one version
to somebody who wanted to build a good Fetzilla
it would now be the circuit below.

It should be stable and sound good.
H2 second harmonic is dominant, follow by H3
Should not need any compensation cap.

I would be pleased to see someone try it out.

is" recommended" better than "ultimate" (post 612)??

 

[Onvinyl]

Did someone make the effort to measure (or simulate) an amp with Speakers (cable, crossover, drivers) connected and see what happens?
Though I would certainly not spend my speakers for a 20kHz full power square wave measurement...

Rüdiger

 

[jkeny]

Perhaps Galvanic Skin Response to measure internal stress levels as mentioned here http://www.diyaudio.com/forums/ever...erceived-distortion.html?highlight=subliminal (Forget about the thread title - I believe it's wrong)

.......Perhaps it is impossible to have an amp with zero higher order content so we have to make sure there is enough low order HD to mask the remnants of the higher order harmonics - which are effectively low level noise.

Sounds feasible to me.

It would seem to me that the study of psychoacoustics is the missing link in all these objectivist Vs subjectivist debates. After all, we are using a flawed instrument to pick up the sound waves (our ears) & then manipulating it through both the ears mechanical & physiological machine before processing it into a subjective experience. Maybe a deeper study of this machinery (psychoacoustics) will bridge the gap between these two camps?

In the absence of this it would seem prudent to go with what sounds best! Full praise to SWF, Lineup, Hugh, etc for this amplifier - I just have a couple of lateral devices from Class-D single & double die that I might try.

 

[mikelm]

John Linsley Hood judged amps with the help of his cat . . .

. . . upon playing several different 1960's transistor amps - with good paper specs - the cat promptly walked out of the room ! with the simple class A, the cat stayed put.

 

[AKSA]

I have been guided by the ghost of JLH's cat for a long time.....

Owzat for moving across to the dark side?

C'mon, Wahab, get yer ya yas out!!

Hugh

 

[jkeny]

I use my cat to do differential calculus on the circuits I am testing - works a treat every time!

I'm guided by a signal in the heavens.
I'm guided by this birthmark on my skin.
I'm guided by the beauty of our weapons.

 

[AKSA]

John,

It is always a pleasure to see you in a thread, top 'o the mornin' to ya!

Hugh

 

[jkeny]

Thank you Hugh, a pleasure to see you here too. Let the mutual back-slapping fest begin 🙂

 

[a1greatdane]

VAS Mos Fet

Dear All,
is there any chance that somebody could be cared to try the suggested Toshiba Part for VAS (2SJ-313)?
I have tried various versions of the the HexFet variety and the the small TO-220 Hitachi's, but did not like the results much...
I have however tried the Big TO-3P Toshibas (2SJ200 & 2Sk1529?) for Output devices, with suitable temperature compensation and that was very good indeed, so there could be a hopeful chance, that this could be the case for the VAS stage as well?😎
Best regards
DocO

 

[MiiB]

Renesas still lists the TO220 devices like SK 216 SJ79 as active....It that so..or am I missing something...?? If still active and possible to get hold of they could be just the thing for the VAS....

I believe this amplifier over time will turn into a new classic like the Zen or Hiragas designs (though only reinvented from the HOOD)

 

[lineup]

I think most will use IRF9610. (TO-220)
It works good enough.
Little ZVP3310A (TO-92) is a tiny bit better.

If we could buy 2SJ79, of course some can try it.
I have downloaded a SPICE Model for 2SJ79.
But unfortunately it gives error.
If any of you have working model for 2SJ79/2SK216
so please post it.

Wild idea.
Use one big 2SJ162 for VAS instead of IRF9610 ???????



Here is the model I do not get to work:

.MODEL 2sj79netliist PMOS (VTO=322.944M KP=20U L=2U W=3.50594M GAMMA=0 PHI=600M
+ LAMBDA=24.1203M RD=1.88227 CBD=1.6459N IS=10F CGSO=1.13517N CGDO=1.13517N
+ TOX=0 NSUB=0 TPG=1 UO=600 RG=50 RDS=1MEG)

 

[MiiB]

Hi i tried to simulate with the SJ79... The distortion 2.3.4 climbs to higher levels...especially when you push the amplifier..at 5 V peak to peak the result is 0.03% vith almost only 2. (-68dB) and 3. (-110dB) harmonic...the higher order comes out lower than 135 dB...

when you go to high amplitudes close to the rails you get a higher distortion off app 0.3%.. but still with excellent distribution...

 

[wahab]

John Linsley Hood judged amps with the help of his cat . . .

. . . upon playing several different 1960's transistor amps - with good paper specs - the cat promptly walked out of the room ! with the simple class A, the cat stayed put.

Assuming it was a male sex cat, should the speaker reproduce
the sound of a female sexed cat, he would have stayed even
with a 80% distorted signal...😉

 

[sng001]

If I was to recommend one version
to somebody who wanted to build a good Fetzilla
it would now be the circuit below.

It should be stable and sound good.
H2 second harmonic is dominant, follow by H3
Should not need any compensation cap.

I would be pleased to see someone try it out.

Hi lineup,

I would like to try the recommended version of fetzilla. I have most of the parts except the IRF9610. I do have a few PMOS to try first, I will order the proper VAS MOSFET if the trial sound good.

I will not use the input cap (C2), will substitute that with a 1K resistor. I use only a 25K pot & so I will increase the R8 to 100K. Otherwise I will build as shown in the schematics.

Cheers, Stanley