Papa! I want to have Zen V5.

[Zen Mod]

...............

And, had another measurement -- clipping point. The symmetric clipping was starting from the point of about 34V pk-pk output ^^.

I bet that's loud enough for your spks 😉

 

[Babowana]

I bet that's loud enough for your spks 😉

Yeah . . . loud enough.
In general, I kick the aass high up during weekend.
But, never at the top.
I want to respect my Japanese neighbours ^^~

 

[Babowana]

~oo~


At amp's work with 25V pk-pk output to the 8 ohm load, I
measured differential ac voltage swing at R3 and R4. Actually, R3
and R4 are trimming pots. But, I roughly calculated adjusted and
fixed values as R3 of about 260 ohms and R4 of about 380 ohms.

Measurement results are 520mV pk-pk at R3 and 2000mV pk-pk
at R4. This means that R3 has less ac voltage swing than R4. If I
calculate these voltages to swinging current, R3 has 2mA pk-pk
hile R4 has 5.3mA pk-pk.

Interesting!
Due to these unbalanced ac current swings between R3 and R4,
the complementary power fets also amplify different ac currents.
As a result, the upper p-ch fet works like an Aleph CCS -- i.e. as
an active current source! And, the lower n-ch fet works like a
single ended amplifier.

Really, an intersting finding. I hope I am correctly understanding
the reason why it works like this babo ^^. But, a good sounding
babo ^^.

 

[jupiterjune]

Babo-

Not sure if you posted this somewhere, but I could not find it--what is the dc voltage on the gates of the jfets?

Also--what are voltages at sources of jfets?

I have been looking at your postings trying figure out exactly how that circuit works.

Also--I am looking at BOSOZ with jfets (2n4416) operating above IDSS to see how what happens.

JJ

 

[Babowana]

Not sure if you posted this somewhere, but I could not find it--what is the dc voltage on the gates of the jfets?

Also--what are voltages at sources of jfets?

Zero volt at the gates. And, see post #217.

 

[jupiterjune]

OK-

It just looked suspicious that the J310 had lower gain than the 2SJ108GR.

I thought the 2SJ108GR might be reverse biased, but I guess not.

I could not find a spec sheet for the 2sj108GR--what is the Gfs listed for it?

I found spec sheets for the j310 -- it listed Gfs as 8 minimum.


JJ

 

[jupiterjune]

oops--

I thought the 2SJ108GR might be reverse biased, but I guess not

I meant to say "I thought the gate of the 2sj108GR might be forward biased..."

 

[Babowana]

I could not find a spec sheet for the 2sj108GR--what is the Gfs listed for it?

I found spec sheets for the j310 -- it listed Gfs as 8 minimum.

There is no separate datasheet for 2SJ108GR.
The datasheet of 2SJ108 covers all.

2SJ108GR has Yfs (Gfs) as 8 min and 22 typical.

 

[Babowana]

The measurement given in post#223 was from L-ch block.
Okay, here is the same measurement from R-ch block.
The measured values from L- and R-ch are very similar ^^,

 

[Babowana]

Here is another measurement from R-ch block.

The current swing at R9 is 0.6A pk-pk
while the swing at R11 is 2.82A pk-pk.

So, my Babo Zen is working similar as SE.

Steen, are you ready to drop ya jaw down to ya foot?


😀

 

[Zen Mod]

Here is another measurement from R-ch block.

The current swing at R9 is 0.6A pk-pk
while the swing at R11 is 2.82A pk-pk.

So, my Babo Zen is working similar as SE.

Steen, are you ready to drop ya jaw down to ya foot?


😀

you made Aleph

 

[Babowana]

you made Aleph

No, no, no

Exactly, Babo Zen Aleph-J


😀

 

[Babowana]

This will be my last post about the characters of the amp.
I find damping factor about 12 with 8 ohm load.
Output impedance is about 0.7 ohms.

Through this project, it seems that I have learned many things.

I am really pleased not only with the excellent sound, but also
for the good lesson about JFETs. Now, I have quite reasonable
self-confidence for the future application of them ^^.

Thanks, to all guys who have kept interests in the progress of
this project. And, special thank you, Papa . . . ^^.

 

[Zen Mod]

nice smell Babo.........

now I must do something with little critters to make you happy

nice little amp,perhaps?


did I told ya "tnx" ?

 

[Babowana]

Don't mention tks.
Smoke not too much ^^.

The bent legs are due to the tests I had.
Any one is found wrong, I will re-send free ^^.

Enjoy!

 

[Babowana]

~oo~


Before I leave this thread alone, few more things . . .

I replaced the two breadboards pictured in post #189 with my own PCB. My own PCB? Yes, my first try after my birth to this beutiful world. Last time, when I was measuring the oscilloscope responses, once I mishandled the probes and saw some of smoke from one of these beadboards. After the probes having been removed, I found that the amp was still working normal. But, I felt as if I were keeping the aching tooth. This was why I wanted to replace them with new boards and new components--but this time with diy PCB.

I cut the copper-clad board to the sizes, using the snap-off blade knife. On the copper side, I made the drawing of black wires with oil pen. Art work? No, not really. This was just a baby who stood up for the fist time. ^^

 

[Babowana]

And, I put the boards into a plastic bowl with some of white cristals of Ammonium Persulfate, then added warm water of about 6-fold amount of Ammonium Persulfate. About fifteen mins. later, I put the boards out of the bowl and washed off them clean. It seemed that I kept the boards in the bowl too long. I found that the left copper layer was looking thinner than I expected.

 

[Babowana]

Hmm . . . the copper layer looked really thin so that I applied solders on it all the way before I made the 1mm through-holes. Then, I inserted components through the holes and soldered them all. Done! It was so easy. It took less than three hours for all.

By the way, This time, I picked up two "smaller" 2SJ108GRs having Idss of merely 5.45mA. Sure of 5.45mA? Sure. Nevetheless, the amp returned back to the same work as previous. No joke! WoaHahahahahaha . . . ^^

 

[john65b]

This thread has been quiet for some time, but would it be possible to sub a 2SJ74 (N ch) for the J310 and a 2SK170 (P ch) for the 2SJ108 in this circuit??

 

[Babowana]

This thread has been quiet for some time, but would it be possible to sub a 2SJ74 (N ch) for the J310 and a 2SK170 (P ch) for the 2SJ108 in this circuit??

Sure. Actually, the combo of 2SJ74/2SK170 is the better answer.
My latest V5 has 2SJ74 and 2SK170.

I had to use J310/2SJ108 as I could not get 2SJ74/2SK170 that time 🙂