Jfet BOZ

[lovechild]

Originally posted by Zen Mod



20log(100/6)

I knew there's a hidden factor (or at least hidden to me), wherever it's coming from.

thx!

[Zen Mod]

Originally posted by Vix
Hi,

............(Secret revealed: I am getting married on 1st of July!!!). ...........................
Best Regards

Vix

p.s. Steen, where are you? Secretly building it?

congrats!!

hehe ,soon you'll be like we all (ok- majority of us)....

kiddin' off course .........

steen is on vacation in Greece,few days more .......

[Vix]

Originally posted by Zen Mod



congrats!!

hehe ,soon you'll be like we all (ok- majority of us)....

kiddin' off course .........

Thanks! Well, since we agreed that the amps and speakers are going to stay, I hope it won't be that bad

(She didn't have anything against a set of BIBs either, but an OB with B200 and 15" woofer will have to be negotiated; New Jfet BoZ from Papa is considered to be an important ingredient to achieving better sound quality-increasing the chances that She will allow even an OB )

p.s. There are no grills on the speakers yet. I guess I've got enough time to solve a potential future problem.... (kidsfingersondustcaps)

Regards,

Vix

[Manu]

Done.

Oh I forgot drilling.

Manu.

[mpmarino]

steen is on vacation in Greece,few days more .......

Well, that explains it. I was beginning to worry if he was ok


Edit: Board looks real nice Manu...

[Manu]

Mr. Pass,
would You also throw out of your magician sleeves something like an ALEPH L JFET?
I love this pre as is, but he wants to be JFETized too.

Manuel

[Babowana]

Originally posted by Vix


(Secret revealed: I am getting married on 1st of July!!!)

Mmm . . . you are going to sign the declaration of life time war . . .
When she (I believe "she") does blabla . . . just shut up your mouth and wait to the end of the blabla . . . offer her a cup of water . . . then you win . . .

Congratulations!!!

[Nelson Pass]

I measured the circuit this afternoon, and it came out mostly
as expected, but the best distortion numbers came from a
16V supply value.

[Babowana]

What are the values, 0.1, 1 and 2 in hor. axis, Papa?

[lineup]

Originally posted by lovechild

I knew there's a hidden factor (or at least hidden to me), wherever it's coming from.

thx!

20 x log(100/6) = ??? (dB gain)
where dB is the level, the volume we actually are supposed to hear

( deci - Bell, Bell is probably the same man who invented telephone , which was the first time we could HEAR, in very long distances.
before this was 'Morse' another Man, who made some way to communicate via electrical impulses, Short and Long. = Telegrafi.
But this did not invlove actial sounds)

correct formula to get the dB, in this case:
1. Where Rs = 10 Ohm (source resistor)
2. Where Rjfet ~50 Ohm ( an imaginary resistor, representing the JFET characteristic.
3. Where Rd ~1000 Ohm (actually 991 Ohm, like )
( the paralleled value of 2k2//2k2//load, where load is selected to be 10k, which is some 'worst case' in put impedance of a 'thought up' power amplifier )

Now the combined load resistance as seen at junction of DRAIN = output
is paralleled values of: 2k2 resistor 2k2 resistor and this 10k Ohm.
Formula for getting this drain load into one value:

Rd =

1
------------------------------- ~ 991 Ohm
1 1 1
---- + ----- + ------
2200 2200 10000

If you go back to my first post, I think I mention this value. 900 Ohm something.


Now voltage gain is roughly Rd / (Rs + Rjfet)

We get 991/ ( 10 + 50 ) = 991/60 (which is almost 100/6)
Gives ~ 16.51 times higher voltage at output, compared to input
if the power amplifier side has 10 kOhm input impedance.

GainV = 16.51
now, people can not hear Voltage. Like with morse telegrafi this just electrical impulses.
They have to be translated into Air pressure Changes, for example in a Loudspeaker.
And how strong a Sound is ( SPL = sound pressure level )
is measured in deciBel ...
I am beginning to think this has nothing to do with Alexander Graham Bell. There must have been a french guy called Bel, or something whpo was heavily into the business of exploring sounds.



Now the relationship between VoltageGain magnitude and sound increase level
is this formula, as been posted by friend Zen Mod:

Gain in dB = 20 x { Log10( GainV ) }

GainV = 16.51
gives Log10 ( 16.51 ) ~ 1.217
x 20 = 24.35 dB

The amplifier will have a gain of 24 dB
.. or more correct -24.35 dB
... negative sign to tell that the signal at Drain, will be opposite Phase of input.

We call this type of amplifier Inverting Amplifier.

If we use 2 transistors in same configuration as JFET BOZ here,
and let it pass both in series, we get the signal back to normal.

The combined gain of using 2 modules after each other would:
- - (24.35+24.35) = +48.70 dB

As two - make one +

for Decibel you simply add the gain.
And expressed in VoltageGain, you multiply.



Therefor 16.51 x 16.51 = +48.70 dB
A gainV of 272.58 !

Put +0.005 Volt (5mV) at input and get +1.36 Volt at output!
This combined 2 modules amp would be suitable as a Microphone .. at least regarding GainV.



lineup do not claim this article to be fit for a Book on the subject. Far from
But you get the picture, if you can dis-regard the use of terminology, in some lines.
... it is not that easy all the time, you know,
when youre bound in writing/thinking fast .. in a FOREIGN Language:
like British english