Let me lite fire - Nelson Pass F1

[GRollins]

When you apply the Aleph current source to the SOZ you begin to approximate the topology of an Aleph-X, assuming that you close the feedback loop to get the "X" part. Yes, it's a promising path.
Remember that the Aleph CCS has a feedback loop (the current-sensing connection that makes it an Aleph instead of a normal CCS). Those who intend to build a non-feedback circuit will want to keep that in mind.
Me? I don't mind modest amounts of NFB once in a while. It's the 50dB stuff that drives me nuts. The longer I mess with electronics, the less I use. I'm down to 7dB at last count, probably headed for zero. (Less than Nelson...that's Charles Hansen territory. Hope he won't mind me barging in.)

Grey

 

[Nelson Pass]

We had this discussion about feedback - even the constant
current sources are using it, so I don't include it as outside
the signal path.

 

[jh6you]

Reference Rev.4.1, post#100


Doesn't matter . . .
Whenever necessary . . .
Can change Aleph current source to ccs easily . . .
There is good flexibility . . .

I will start with R3/R4 with 10K.
R1/c1 and R2/c2 will switch their positions.
R1/R2 will be 2K for about 14dB gain.
c1/c2 will be 47uF.

Input impedance would be low.
It's not my concern.

Output impedance . . .?
I don't know.
The Aleph curent sources would reduce it.
Because they provide negative impedance, acc. to Nelson.

I will try to drive ordinary speakers.
And will see.

Any of your comment?
Appreciate it.

Regards
jH

 

[jh6you]

And power unit.


Many might say no good . . .
Anyhow expect comment . . .


Regards
jH

 

[jh6you]

LED on . . . its location is not final tho . . .

Measured . . .
Rail : 23V
Drain voltage, gain mosfet: 14.4V
Gate voltage, gain mosfet: 8.5V
CCS drain voltage: 3.44V

All other paths similar values . . .

(R5 and R6, not 8.3k, but 7.5k)

Offset: 5mV/34mV
No turn-on turn-off pop noise . . .
Dead quiet with no signal . . .

Sound . . . ?
Do I really need the efficient single drive speakers . . . ? ? ?

I'd like to wait until the new smell is washed off . . .
I will come back . . .



Only concern is the gain is somewhat low . . .
I might reduce R1 and R2 from 2k down to 1k.
Or, I might increase the gain (unity at maximum) of my BOSOZ . . .

Nelson, which way do you recommend?

Regards
jH

 

[john-china]

hi ,jh6you

i knew your transformer ,but did not ever use ,
so i want to know , do you like it ? is it ok for your class A amp,
is there any hum or buzz ,heat .

 

[jh6you]

Hi,

No hum, no buzz.
I'm fully satisfied with.

Regards
jH

 

[moe29]

jH,

I always love the look of your finished amps

great work, hope you enjoy... and thanks for sharing your ideas
and work, always a pleasure to read.

 

[jh6you]

Thanks, moe29.
Actually, the ideas are originated by Nelson.
It must be that all of us think so.


Changed R1 and R2 down to 1k . . .
Now the gain is enough . . .
I find that the circuit is the same as Zen V7 . . .
Except that the 8 ohm loads are replaced with Aleph current sources . . .
and that the subtle tweaking in btm ccs . . .

I wonder mine is still a current source amp . . .
Or a voltage source amp . . .
Or in the middle . . .
Anyhow, the sound is "special" and very good for me . . .

I wonder why they say the Pass Firstwatt F1 is 99% not fit
for the ordinary speakers . . .
My ears are deceiving me . . . ? ? ?
Or my speakers are included in the remaining 1% . . . ? ? ?
Am I so lucky . . . ? ? ?
I was about to order Lowther corns . . .
Now, hesitating . . .

I really would like to know . . .
If the ordinary speakers are not fit . . .
In which areas the problems would exist . . . ? ? ?

I'd like to cure my ears . . .
Give me your help . . . please . . .


Regards
jH

 

[jh6you]

Regret . . .
I should have built two . . .
One for Pass original and another for mine . . .
Mmm . . . I can hardly give up mine . . .


I think that Nelson has built his F1 for demending owners.
He has considered even the LED completely turning off.
Bleeder . . .
And, safety . . .
I could say only this: "Nelson is Nelson."

Now I feel free to post mine as built.
I think it must be a voltage amp.
BOSOZ (of abnormal form) drives this amp.
And, the amp drives nominal 4ohm 90dB speakers (paper corns).

I feel noise level is very low.
All different music frequencies are clean and well forcused.
And, pleasently tight . . .
Bass starts from many steps behind and runs to the front.
I feel the damping factor must be low.
It seems, however, working positive way.

I will test more with different types of music and try to post about my feeling . . .

Regards
jH

 

[apassgear]

I think it must be a voltage amp.

[jH

Looking at the schematic it appears to be.

But good if you like your variation. Happy hearing

 

[Nelson Pass]

Now I feel free to post mine as built.
I think it must be a voltage amp.
BOSOZ (of abnormal form) drives this amp.

I would suggest that you try lower values for P2, R25, R26.
You will note that I used low values in order to compensate for
the capacitance of the bottom current source. We note that
Mosfet's capacitance becomes greater and more non-linear
as the Drain-Source voltage gets low, and a lower impedance
in these resistors (so that the gate sees 100-221 ohms) will
improve the high frequency performance, particularly with single
ended input. As you are using a balanced input with BOSOZ
(perfect match, I think) this is less of an issue.

 

[jh6you]

Thanks, Nelson. Well understood.
I will surely lower them.


I walked through the entrance of the plane . . .
Looking at your F1 . . .
Why no R at the gate?
Why the R and P are so low?

2 hours later . . .
I walked out of the exit of the plane . . .
Understanding nothing . . .


Cheers!
jH

 

[jh6you]

Removed R25, R26 and R27.
Lowered R28 and P2.
Removed the thermistors located between the bridge diode and psu caps because I found a problem there . . .


Wow !!! Wow !!! Wow !!! Yeahhhhhhhhhhhhhhhhhh . . .

XA-160 . . . ?
Give me the way !!! Sorry, Nelson

Remaining three days will be too short . . .
Would like to threat my boss for more holidays. . .

Best Regards
jH

 

[jacco vermeulen]

Nice combo, JH, exceptional design.

Mind telling what you intend to drive with it?
How much are Fostex or Lowther drivers where you live?

 

[jh6you]

Thanks, jacco

It is now driving Audio Physic's bottom model, Yara.
I want to buy Lowther PM6A, but price here is USD1850/pair
I'd like to order them from the land over the sea.
Still thinking what to do . . .
I want to build J-low, if possible, or Voigt pipe.

My sons are careful in commenting on the sound of my diy amp . . . But, this time . . . different . . . both of them say: "Two thumbs up!!!" "Distinctively wonderful!!!" . . .
It drives Yara suprisingly well . . .

Regards
jH

 

[apassgear]

It is now driving Audio Physic's bottom model, Yara.
I want to buy Lowther PM6A, but price here is USD1850/pair
I'd like to order them from the land over the sea.
Still thinking what to do . . .
jH

JH,

Have a look to what they are saying about the FR125 from CCS on the fullrange forum. This at 1/10 of the PMA6A. Save the rest for a real F1 (clone of course) to compare... or buy a new F2...

 

[jh6you]

Thanks for the info, apassgear. I will check it.

By the way,


From the L-ch speaker, my ears detected one ignorable thing . . .
Hmm . . . what's wrong . . . ?
Suspected the npn transitors (ksp42) . . .
Replaced one of them . . .
Now okay . . .
Remeasured all nodal voltages . . .
Exactly to my expectation . . .


I contacted Mr Manfred Diestertich, Audio Physic, about my Yara.
According to him, the current source amp will show up more in bass. The bass will be uncontrolled. It makes no sense to modify an existing design to use it with a current source amp.

Therefore, I carefully evaluate the music, particularly, with respect to the bass, i.e. wondering whether the bass would collapse or not. I tried Tchaikovsky Violin Concerto, Victoria Mullova and Seiji Ozawa, particularly focusing on the bass. Collapse . . . ? No! Not at all!

I see the nice stage of the concert hall. Players are lovely and warm and sweet. Mmmmmmmmmmmmm . . . that's it.

Regards
jH

 

[jh6you]

Listening to Mahler Symphonie No.4 . . .
Reading Nelson's paper about Jordan . . .
I'm seriously interested in J-low . . .


Nelson, have you ever listened to J-low with any other driver?
If no answer to this, mmm . . . will order a pair of JX92S.

Regards
jH

 

[Nelson Pass]

I have also used the J-Low with Fostex (208 E Sigmas (early),
FE206E, and FE166e), Mangers, and Lowthers (DX4 and DX55)
with good enough results. Each of these drivers requires
different stuffing and/or damping factor on the amplifiers, and
often a bit of Eq, but then that is true of any kind of box.