120 Volt psu PreAmp - lowest possible G-FeedBack

[fotios]

But with 120V!! supply??
I was tried up to +/-35V supply in my discrete preamp.
Lineup has allways big surprises to all of us!
There is a nice ancient Greek word with poor translation in English that suits to Lineup:
ÑÇÎÉÊÅËÅÕÈÏÓ
It is a compound word, composed from the ancient Greek verb: ÑÇÃÍÕÌÉ = I OPEN and the word: ÊÅËÅÕÈÏÓ = WAY.
In Oxford Greek-English dictionary it is translated as: enterprising or forward-looking.
Thus, a better meaning it is: The man who opens new ways.

Fotios

[lineup]

.
In this amplifier, the open loop gain is = closed loop gain.
What this means, is that we have not very much voltage gain, totally.
Closed/Open loop Voltage gain is = 20 (+26dB)
This was chosen for 20 Volt RMS output at 1.0 Volt RMS input signal.

Now, I have 2 stages at hand for making x20.
( The output stage is one buffer gain ~1.0 and put OUTSIDE the fb-loop).

I could go several ways:

A)
> Input stage: x1
> Second stage: x20 ... makes total v-gain x20
B)
> Input stage: x20
> Second stage: x1 ... makes total Gv=20
C)
> Input stage: x2 ... to ... x10
> Output stage: x10 ... to ... x2
all makes total Gv=20

For reasons that are Lineup Audio very secret IP, Intellectual Property,
and completely unknown to public society I went for Option C).
See today's Attachment

Lineup Audio LAB MEMBERS Access to our IP = Secrets!
Lineup Audio LAB MEMBERS Access to our IP = Secrets!

[lineup]

.
Helloooo!!!!

If you wish to get more into details
of this lineup audio project,
then please
Get your own account (same username as here)
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[AndrewT]

Originally posted by lineup
and discuss this project and many other
at our nice new audio forum - for audio designs

Link, if you have not Bookmarked:
http://lineupaudio.freehostia.com/forum

Look for topic
The 120 Volt PreAmp project
... in forum category

no, no and no.
We choose to be here and you can't tell us where to go.
Just ask. No demands.

[lineup]

.

.
Comparing FFT Analys
without (blue) vs. with Low Feedback (red)
At 1 .0 Volt RMS input and
20 Volt RMS output ( +- 28.3 Volt Peak )
.

Notice, that this is NOT negative global feed back,
as Output Buffer is outside feedback loop.

We can call it Local Feedback, including input + second stage.
And the Fourier Results are from the output from third stage.
From the output Buffer Emitter.

Enjoy
Lineup

[fotios]

Originally posted by AndrewT
no, no and no.
We choose to be here and you can't tell us where to go.
Just ask. No demands.

Very good.

This is a reply expressing the traditional Scottish stubbornness (with the good sense of the word) with a spice of humour (at least to me, maybe Andrew does not perceive his saying such and i ask his forgiveness)
Consequently it is not for misunderstanding.

Peace

Fotios

[lineup]

Hi!
I am currently working on the upper rolloff.
Looks like it will be possible to get something like 400 kHz.
With stabilty.
This is not bad for such low feedback
and considerable voltage gain ( Gv=20 ).

Be back with some AC Analysis graphs. Frequency curve + Phase.

Lineup

[lineup]

Originally posted by lineup
Hi!
I am currently working on the upper rolloff.
Looks like it will be possible to get something like 400 kHz.
With stabilty.
This is not bad for such low feedback
and considerable voltage gain ( Gv=20 ).

Be back with some AC Analysis graphs. Frequency curve + Phase.

Lineup

According to several respected diy audio members
an upper bandwidth of like 100-150 kHz is enough.
As they have put it to me, they say they can accept
-0.1 or -0.2 dB at 20000 Hertz.

What do you say

Are you happy, as I am,
if I rolloff this 120 Volt pre amplifier with -0.2 decibel at 20 kHz.
I canput it this way:
This amplifier will at maimum have -0.2 dB at 20 000 Hertz, the upper Audio Band.

Any opinions welcome.
Lineup

Lineup Audio LAB

..... projects, audio, discussions, schematic, pcb, designs, audio

[lineup]

OK
I settle for -3 dB at 100 000 Hz
as no body has got some other opinion on this.

= will be more than I can hear with my ears

We may have to change this roll off frequency
if John Curl comes to visit me

[lineup]

.
I have been doing some stability tests.
10 pF across the feedback resistor
seems like be enough.

May change, but for now I will be using this 10 pF trick.