Jfet BOZ

[Babowana]

Originally posted by Nelson Pass


It really helps if you have any kind of distortion analyzer . . .

I wanted to build one analyzer as you guided, but . . .
Will buy one 2nd hand when I arrive home tomorrow . . .
Many new interesting projects here while I have no time till end-year . . .
Half sad, another half happy . . .


I'm leaving China behind 4-year staying. Time is flying.
As usual, bringing only good impressions to my future.
Good bye, Kina . . .

[twitchie]

It's getting very late, but I remembered I have Veteran's Aleph P1.7 and took one of the supply boards and jumpered after the third 9.1V zener ...

In summary, it sounds pretty good on the jury-rigged system I'm testing with right now - and I'm back to all stock values, except I have the rail voltage at about 19V and getting about 6.8V across the jfet.

Stephen

[steenoe]

Originally posted by Manu






And nobody trust me when I say I am stupid.

Reconnected hot to hot and : Oh Lord!!! This sound. Plenty, full, seductive, and cristal clear.

Danke Meister
Danke Steenoe.

It is realy great.

(But I have to crank the volume allthe way up
)
manu

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

[Vix]

Originally posted by steenoe
Manu, with your enthusiastic review I think that I will make a quick mockup and connect it to the F4

Steen

Most probably you'll make that quick mockup before I do mine

I'd like to do it this weekend..but I can't promise...

As you probably saw, it will be run out of two 9 v Ni-Mh rechargeable batteries. I measured them and they actually have around 9.5 v. So the pre will be run at about 19 v. I also expect to adjust resistor values. What about inserting a 2 k trimpot in series with, say 1 k Drain resistor, and tweak for best sound? (I don't have a distotion analyzer,my ears will by my guide)

Babowana, I wish you good luck, wherever you're going. By the way, is it going to be a bit difficult to move those big speakers? (it was J-low, right?)

Regards,

Vix

[Zen Mod]

Originally posted by steenoe


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

now we are in R. Johnson's territory ........we trade simplicity of preamp for necessary complexity of PSU

either Noro shunt , sort of super reg , or battery .
battery is least complicated version

[cviller]

Originally posted by Manu
For recall my setup is now:
Source res: 22R
PSU 17 V
May be the 2K2 hare to be adjusted.

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.

[Zen Mod]

Originally posted by Zen Mod


..........toss entirely that volume on output.......................

[cviller]

..........toss entirely that volume on output.......................

Did it happen? I might have gotten lost in all the girl talk!

[Zen Mod]

Originally posted by cviller


Did it happen? I might have gotten lost in all the girl talk!

they (sheeeeeeeeeeesssssssss) are even more important than our toys

[steenoe]

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 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