If I can, I want to see.
If I can, I want to catch.
If I can, I want to know.
My eyes are black out.
I can feel only few yellow stars in the darkness of my head.
The music is still dancing . . .
I measured bias voltages across R5 and R6.
0.203V across R5, i.e. bias current is 20.3mA. Hmm reasonable.
0.129V across R6, i.e. bias current is 12.9mA. Huh . . . ?
From another chanel,
0.196V across R5, i.e. bias current is 19.6mA. Hmm okay.
0.124V across R6, i.e. bias current is 12.4mA. Eng . . . ?!?!
How come???
I measured the current of 2SJ108GR with Rs of 10ohms.
It was 4.5mA before installation of them to the amp.
But, how could I get 12.9mA and 12.4mA?
Papa, is this kinda ghost effect?
If I can, I want to catch.
If I can, I want to know.
My eyes are black out.
I can feel only few yellow stars in the darkness of my head.
The music is still dancing . . .
I measured bias voltages across R5 and R6.
0.203V across R5, i.e. bias current is 20.3mA. Hmm reasonable.
0.129V across R6, i.e. bias current is 12.9mA. Huh . . . ?
From another chanel,
0.196V across R5, i.e. bias current is 19.6mA. Hmm okay.
0.124V across R6, i.e. bias current is 12.4mA. Eng . . . ?!?!
How come???
I measured the current of 2SJ108GR with Rs of 10ohms.
It was 4.5mA before installation of them to the amp.
But, how could I get 12.9mA and 12.4mA?
Papa, is this kinda ghost effect?
Babowana said:If I can, I want to see.
If I can, I want to catch.
If I can, I want to know.
My eyes are black out.
I can feel only few yellow stars in the darkness of my head.
The music is still dancing . . .
I measured bias voltages across R5 and R6.
0.203V across R5, i.e. bias current is 20.3mA. Hmm reasonable.
0.129V across R6, i.e. bias current is 12.9mA. Huh . . . ?
From another chanel,
0.196V across R5, i.e. bias current is 19.6mA. Hmm okay.
0.124V across R6, i.e. bias current is 12.4mA. Eng . . . ?!?!
How come???
I measured the current of 2SJ108GR with Rs of 10ohms.
It was 4.5mA before installation of them to the amp.
But, how could I get 12.9mA and 12.4mA?
Papa, is this kinda ghost effect?
R1 is convenient path for additional current paths of both jfets;
that fact can explain difference in currents;
why they have different currents than in bench test..........dunno........you must tell that........sources and gates aren't exactly common-grounded
btw-who cares-at least if they sing the song ,and survive..........
and-few more words,after few days-how it sings?
Zen Mod said:
A fresh mint is sneaked in.
I listen to one of my favorite CD, Tchaikovsky Violin Concerto,
Viktoria Mullova violin, Boston Symphony, Seiji Ozawa.
When I listen to the music, I like to imagine the stage.
I see each and all of their movement more clearly, and closer
to me touching my sense of pleasure. Mmm . . . my ears are
singing too.
I feel the same with Blues, Jazz, Bob Dylan, ZZ top . . .
I will try Goldfrapp tomorrow ^^ . . .
PS.
It's still unbelievable! I could't figure it out. It is true that
0.129V across 10ohms means 12.9mA through it, isn't it?
But, through 2SJ108GR classified with Idss ~2.6mA-6.5mA.
And, the bench test showed me 4.5mA with the 10ohm-Rs . . .
To be sure for my bench test results, I again measured Id of
63 pcs of 2SJ108GR tonight. The mesurement set-up is sketched
in the attachment. Yeah . . . all of them apparently show Id values
lower than 4.4mA.
As far as I understand, the jfet is a variable resistor which is
controlled by three voltages--Vgd, Vds, and Vgs--because
they build up the depletion regions in the p-channel (or n-channel).
Most probably, the current source (J310) connected to the
2SL108GR is forcing the depletion region thinner? So, the Rds is
forcefully reduced causing the increased current through
2SJ108GR? Still scratching my stone head . . .
Anyhow, the amp pumps up the nice music.
63 pcs of 2SJ108GR tonight. The mesurement set-up is sketched
in the attachment. Yeah . . . all of them apparently show Id values
lower than 4.4mA.
As far as I understand, the jfet is a variable resistor which is
controlled by three voltages--Vgd, Vds, and Vgs--because
they build up the depletion regions in the p-channel (or n-channel).
Most probably, the current source (J310) connected to the
2SL108GR is forcing the depletion region thinner? So, the Rds is
forcefully reduced causing the increased current through
2SJ108GR? Still scratching my stone head . . .
Anyhow, the amp pumps up the nice music.
Attachments
Babowana said:To be sure for my bench test results, I again measured Id of
63 pcs of 2SJ108GR tonight. The mesurement set-up is sketched
in the attachment. Yeah . . . all of them apparently show Id values
lower than 4.4mA.
As far as I understand, the jfet is a variable resistor which is
controlled by three voltages--Vgd, Vds, and Vgs--because
they build up the depletion regions in the p-channel (or n-channel).
Most probably, the current source (J310) connected to the
2SL108GR is forcing the depletion region thinner? So, the Rds is
forcefully reduced causing the increased current through
2SJ108GR? Still scratching my stone head . . .
Anyhow, the amp pumps up the nice music.
who knows-maybe is this way even sweeter for your ears than with proper complementary jfet pair
Babowana said:
No, no ghost.
I had a kirchhoff's rule test tonight.
I made J310 (N-ch) as kind of a current source.
And, I made 2SJ108GR (P-ch) as kind of a resistor.
I picked up one 2SJ108GR (tested Id at 2.2mA) from Group B
in post#206. And, had the kirchhoff's rule test.
The attached picture shows that two different tests were
following the rules. FLUKE shows measured voltages across
Rs of 10 ohms of 2SJ108GR -- 0.115V (11.5mA) and 0.168V (16.8mA).
Now I understand why the 2SJ108GR having low Idss
could have more current inside the amp. Hmm . . .
I would like to make a small report if I can somewhere.
Papa, are you reading my posts?
I didn't make you disappointed, did I ^^.
If you have any comment, please . . .
/PS/
Choky!
Tomorrow, I will send you 20 x J310, 10 X 2SJ108GR from Group A
(picking up random) and 10 x 2SJ108GR from Group B ^^. Just for
your fun ~^^
Attachments
With 8 ohm load, the squre waves are clean.
The mid bandwidth goes up to 250kHz (-3dB).
The amp is simple and straight forward.
Gain is about 4.7
Input impedance is 48K.
The output impedance is not measured.
I have listened to the amp about one week.
"I Won't Grow Up"
Nylon string guitar plays properly bright with slight touch of
night color. Strings are tight harmonics and lightly float in the air.
Her whistling is cute even though the energy is not as much
as Livingston Taylor has in "Isn't She Lovely". ~^^~
. . . . . . . . . . . . . Pop Pop, Rickie Lee Jones
The mid bandwidth goes up to 250kHz (-3dB).
The amp is simple and straight forward.
Gain is about 4.7
Input impedance is 48K.
The output impedance is not measured.
I have listened to the amp about one week.
"I Won't Grow Up"
Nylon string guitar plays properly bright with slight touch of
night color. Strings are tight harmonics and lightly float in the air.
Her whistling is cute even though the energy is not as much
as Livingston Taylor has in "Isn't She Lovely". ~^^~
. . . . . . . . . . . . . Pop Pop, Rickie Lee Jones
Hey Babo -- I think in your later posts you said you figured this out, but if not, here is a good article by EB:
http://www.borbelyaudio.com/adobe/ae599bor.pdf
There is a part 2 article as well.
Nice description of of the sound, I am still mulling over what to build next after I finish re-doing the input stage of my aleph--maybe one of these......
Here are dc values measured.
The amp plays sound better and better.
Probably, my ears are now broken in.
"La Cienega Just Smiled"
Sings melancholy of a city boy. Very good and rich
harmony of acoustic guitar, bass, Piano, drums,
chamberlain strings and vibes.
. . . Ryan Adams/ Gold
. . . mastered by Doug Sax and Robert Hardly
The amp plays sound better and better.
Probably, my ears are now broken in.
"La Cienega Just Smiled"
Sings melancholy of a city boy. Very good and rich
harmony of acoustic guitar, bass, Piano, drums,
chamberlain strings and vibes.
. . . Ryan Adams/ Gold
. . . mastered by Doug Sax and Robert Hardly
Zen Mod said:
Yeah, team and harmony . . . should be always good.
BTW, measured FFT (Fast Fourier Transform) to see the frequency spectrum with the fundamental frequency of 1kHz at 26V pk-pk output. The fundamental frequency was measured as about 65dB, the 2nd harmonic about 22dB (0.7%) and the 3rd about 16dB (0.35%). The amp was looked having quite second harmonics at all different output levels ^^.
And, had another measurement -- clipping point. The symmetric clipping was starting from the point of about 34V pk-pk output ^^.
Attachments
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