Jfet BOZ

Official Court Jester
Joined 2003
Paid Member
steenoe said:
You are right about the supply. Just made a quick drawing of the shunt reg and it ended up with more parts than the gainstage:xeye: So battery power is the simple solution.
2 normal 9V batteries should do the trick for starters.
I also think that its a very good idea to do as cviller suggests and go back to the original circuit and take it from there;)

Steen:)


as I said ...never mind.....- as Papa sez ........

CRO and sig gene will take you "there"

without exact load lines , and for actual jfets they are even more sheeshee than for toobz , you can't do nothing more than draw prototype ; after that ear and little gadgets can tell more .
remember your last proto jfet xccs@#$%**%$ BOSOZ - we started with 9mA per jfet ; you must decrease current.....and now is time to replace IRFs with little bjts ,because IRFs are starving with so weeny current ........
and what- we are again in teritory of half UGS......:bawling:


so- Pumpkin,what else...... :devilr:

ZM- proud inventor of The Boiled Water
 
Zen Mod said:



as I said ...never mind.....- as Papa sez ........

CRO and sig gene will take you "there"

without exact load lines , and for actual jfets they are even more sheeshee than for toobz , you can't do nothing more than draw prototype ; after that ear and little gadgets can tell more .
remember your last proto jfet xccs@#$%**%$ BOSOZ - we started with 9mA per jfet ; you must decrease current.....and now is time to replace IRFs with little bjts ,because IRFs are starving with so weeny current ........
and what- we are again in teritory of half UGS......:bawling:


so- Pumpkin,what else...... :devilr:


ZM- proud inventor of The Boiled Water

Excactly. Why use a power-mosfet for 8mA current? I am sure its better to use smaller devices for biasing/cascoding in the Xccs...and so on... BosoZ. My bet is that "The Pumpkin" will sound great :cool:
The J-fet BoZ is a nice little toy. I will try and play around with it for fun:) Might turn out to be a handy little gadget without the powercord. Looking for a lunchbox right now:D

Steen :)
 
Formerly "jh6you". R.I.P.
Joined 2006
!!! OFFTOPIC !!!


Steen,

Here is Kubota Takashi preamp which I used time ago for my 0dB
power amp (Hitach MOSFETs). You could make PCB if you like ^^.


:darkside:


!!! OFFTOPIC !!!
 

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Vix said:



Even a "STR8" box will work.

:devilr: :D

As long as the lid comes off in a snap, for changing the batteries:D

What is the best way to optimize the loadline without a Distortion Analyzer? I was thinking of installing trimpots like Vix suggested and tweak the values to get the nicest sinus-curves at 1V , 1KHz while watching the screen. Repeating at 10kHz and 20kHz.
Any other suggestions to get the best values Vds/Ids for lowest distortion?

Steen:)

Edit. Thanks a lot JH. Thats a nice schematic, with lots of
J-fets :eek:
 
Official Court Jester
Joined 2003
Paid Member
Babowana said:
!!! OFFTOPIC !!!


Steen,

Here is Kubota Takashi preamp which I used time ago for my 0dB
power amp (Hitach MOSFETs). You could make PCB if you like ^^.


:darkside:


!!! OFFTOPIC !!!


you'll be banned for good if you continue like this;
you KNOW that off topic posts are strictly allowed in threads
started by :
Lucky Luke,Baobabwana,jaccoshmacko,Choky.......mebbe even MetalMasterMag ........

btw- nice one ,even if teuer (but- there is really no point in making any circ non-susy ,if it have more than one transistor :devilr: )

:darkside:
 
Official Court Jester
Joined 2003
Paid Member
steenoe said:


As long as the lid comes off in a snap, for changing the batteries:D

What is the best way to optimize the loadline without a Distortion Analyzer? I was thinking of installing trimpots like Vix suggested and tweak the values to get the nicest sinus-curves at 1V , 1KHz while watching the screen. Repeating at 10kHz and 20kHz.
Any other suggestions to get the best values Vds/Ids for lowest distortion?

Steen:)

Edit. Thanks a lot JH. Thats a nice schematic, with lots of
J-fets :eek:


http://www.diyaudio.com/forums/showthread.php?postid=1231391#post1231391


there is no other way

study Papa's schematic where he use 2SK170,especially one with cascodes ; see what d-s voltages he use- this is probably (!?? hehe) nice voltage range for them;
try to keep that voltage range ,then adjust current to achieve sym clipping

it's iterative process with varying Ub,Rd and Rs ,presuming constant load;

at least on our level of knowledge :xeye:
 
Zen Mod said:



may I too ,Sir?

please.........


:devilr:

Feel free :)

steenoe said:


Thanks:cool: I better do that. How are your amps comming along? Would be nice to hear them too;)
You better invite Zen Mod too, I am sure he will volunteer being the Grillmeister:D

Steen:)


Nope, no new finished amps. Just because you don't go fishing all summer as you used to, dosn't mean you have the right to dis those of us whom actually have other interests ;)
That project is though moving ahead from time to time, even in the summertime.....

Magura :)
 
Official Court Jester
Joined 2003
Paid Member
Zen Mod said:



.....................
you KNOW that off topic posts are strictly allowed in threads
started by :
Lucky Luke,Baobabwana,jaccoshmacko,Choky.......mebbe even MetalMasterMag ........

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

:darkside:


OK.......... Vixieschmicksie my man included on list!


even if I can't (#$%!!!$$%%#) approach to my lathe,to make him few phase promised long ago plugs
 
steenoe said:
You better include Vix on this list:D

I agree....:clown: :D



Zen Mod said:


OK.......... Vixieschmicksie my man included on list!

even if I can't (#$%!!!$$%%#) approach to my lathe,to make him few phase promised long ago plugs

:cheerful:

Don't worry, it's summertime, it's more important to have an approach to BBQ and grill some nice "cevapi". A beer or two handy...
:cheers: :cheers:

Vix
 
steenoe said:

Now we are getting somewhere:) Nice to see you are making progress. Usually when the preamp is phase-inverting, you will change the phase's at the output of the poweramp to make up for that. (If you think that is necessary).
If you have to turn the volume all the way up, maybe the input pot needs adjustment? If this little gainstage has 24dB gain it really should have more than enough gain for a "normal" poweramp. I am still a bit puzzled, does it really have all that gain?
Manu, with your enthusiastic review I think that I will make a quick mockup and connect it to the F4:) Mayby a nice little shuntreg is the best thing for this pre's supply. I expect it would result in a very direct and precise sound. A cap-multiplier in front of the shunt is probably in order, this simple thing cant have the largest PSRR in the world.

Steen:)

BTW
Here is a simple Distortion "analyzer" . I didnt build it. I am not sure how usefull it is, but Elliot is usually worth consulting.
http://www.sound.westhost.com/project52.htm

Thank you, indeed a distortion analyser would be nice.
As with the phase invertion, OK, :D, I will survive the Ridicule. I wanted to ask about this point before I finished the PCB and I forgot.
I use a Aleph L / P like PSU, its relatively simple and works good. But if you suggest something better I would try it subito.

Please buid the JFET BOZ an report your impression.

cviller said:


Have you tried going back to the initial configuration, now that you have fixed the problem with shorting the "hot" of the two channels?
I think the circuit is intended to have the volume adjustment before - I guess the problem you had with gnd vs hot could have been the one forcing you to have a pot on the output of the preamp.

BTW: Changing the source resistor to 22R should lower the gain to ~22dB, so I guess the problem with turning up the volume is mostly related to the position of your input pot.

Not yet. Indeed with the initial configuration (20V PSU) I had more power (volume at 12 - now its at 3 o'clock ). If I recall right the distortions problems have been solved by appplying Zen Mod suggestions regarding res values/current etc. The GND/Hot (thanks again steenoe) followed and was the next big improvement. But I'am not shure. May be I've made all this changes at the same time (bad method I know)...
In fact, as Nelson said that the distortion figure are best at 16V, I choose to stay around this value (In fact 17V).

But I will try several configurations this evening. Pot/no pot etc... And report. Yesterday after reaching the ground and then be saved in last minute by Zen Mod, I spend the rest of the evening enjoying the sound.

BTW the pot at the output was intended to be some protection for my speakers too, as I don't realy trust the ones I have at input.

> quote: Originally posted by Zen Mod :
..........toss entirely that volume on output....................... <
I'll do it Meister.

cviller said:

Did it happen? I might have gotten lost in all the girl talk! ;)
She is part of the test setup, :angel:

Manu