120 Volt psu PreAmp - lowest possible G-FeedBack
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 29th August 2008, 08:28 PM #21 fotios   diyAudio Member     Join Date: Feb 2007 Location: Δραμα - North Greece 120V!! supply. 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: ΡΗΞΙΚΕΛΕΥΘΟΣ It is a compound word, composed from the ancient Greek verb: ΡΗΓΝΥΜΙ = I OPEN and the word: ΚΕΛΕΥΘΟΣ = 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 __________________ Best Regards FOTIS ANAGNOSTOU
lineup
diyAudio Member

Join Date: Dec 2005
Location: the north
The Voltage amplification, gain stage - VAS

.
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:
Quote:
 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

Attached Images
 120vpre_vas-stage.png (866 Bytes, 302 views)
__________________
lineup

 31st August 2008, 10:36 AM #23 lineup   diyAudio Member     Join Date: Dec 2005 Location: the north discuss this project in our forum - in Our Audio Community . Helloooo!!!! If you wish to get more into details of this lineup audio project, then please Get your own account (same username as here) 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 Lineup Audio Projects Lineup __________________ lineup
AndrewT
R.I.P.

Join Date: Jul 2004
Location: Scottish Borders
Re: discuss this project in our forum - in Our Audio Community

Quote:
 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.
__________________
regards Andrew T.

lineup
diyAudio Member

Join Date: Dec 2005
Location: the north
120 Volt PreaAmplifier - Fourier Comparing Analys

.
Quote:
 . 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
Attached Images
 080831_120v-pre_fourier_compare3a.png (8.7 KB, 293 views)
__________________
lineup

fotios
diyAudio Member

Join Date: Feb 2007
Location: Δραμα - North Greece
Re: Re: discuss this project in our forum - in Our Audio Community

Quote:
 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
__________________
Best Regards FOTIS ANAGNOSTOU

 31st August 2008, 11:16 PM #27 lineup   diyAudio Member     Join Date: Dec 2005 Location: the north 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
lineup
diyAudio Member

Join Date: Dec 2005
Location: the north
Quote:
 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
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lineup

 1st September 2008, 10:37 AM #29 lineup   diyAudio Member     Join Date: Dec 2005 Location: the north 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
lineup
diyAudio Member

Join Date: Dec 2005
Location: the north
Frequency Compensation Capacitance

.
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.
Attached Images
 120vpre_4b_frequency-comp1.png (746 Bytes, 206 views)
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lineup

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