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Old 27th February 2007, 02:02 PM   #1
Tyimo is offline Tyimo  Hungary
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Default ONO variation for AX

Hi!

My friend Cucu built the Aleph X and he is very satisfied with the sound. (Thanks for Mr. Pass and Grey Rollins!!!)
Now he would like to build a preamp with very low output imp and more precise sound then the Aleph preamps with no negative feedback has.
He thought on the Aleph Ono phase shifter circuit as starting point.
His question: need he change anything in the attached schematic?

Greets:

Tyimo and Cucu
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Old 27th February 2007, 03:04 PM   #2
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The input attenuator looks a bit ugly. Increase the 22k to gnd? You may also be able to get rid of the coupling caps. How do you intend controlling volume?
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Old 28th February 2007, 04:11 AM   #3
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Two things:
--I'm not clear whether you're looking for a preamp with or without negative feedback.
--Are the .001uF caps running Gate to Source on the input differential necessary?

Grey
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Old 28th February 2007, 04:47 AM   #4
Tyimo is offline Tyimo  Hungary
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Hi Analog SA and Grey!

Thanks. I will ask him and write the answers soon!

Greets:

Tyimo
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Old 28th February 2007, 06:56 AM   #5
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Further thoughts: having an output stage allows you to use proper FETs for the input pair; all 3 current sources can share the same refence voltage for simplicity.

If you now draw the circuit, guess what's it gonna look like

My interest in this discussion is similar to your friend's: recently bulit a P 1.7 and doesn't look like i can live with it - too rich on the whipped cream and sugar. My first idea was to rebulid it similar to the X2, with a negative supply and at least get rid of one of those wretched caps but keep the ccs loads.
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Old 1st March 2007, 05:29 AM   #6
Tyimo is offline Tyimo  Hungary
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Hi!
Sorry for the late reply, but yesterday I couldn't get into the forum
because of some DIYaudio Server problem.

Quote:
The input attenuator looks a bit ugly.
He thought it is part of the feedback and need for the gain adjusting.

Quote:
The input attenuator looks a bit ugly.
With input pot.

Quote:
I'm not clear whether you're looking for a preamp with or without negative feedback.
He would like to use feedback.

Quote:
Are the .001uF caps running Gate to Source on the input differential necessary?
Maybe it not necessary, but the ONO has this caps and in the ONO there is negative feedback too.

Greets:

Tyimo and Cucu
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Old 1st March 2007, 01:27 PM   #7
Tyimo is offline Tyimo  Hungary
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Hi!
I don't know what is wrong with the DIY audio server!
I wanted post:
Quote:
How do you intend controlling volume?
With input pot.

Sorry.

Tyimo
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Old 1st March 2007, 09:33 PM   #8
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I'd try it without the caps first. Only put them in if you need them.

Grey
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Old 3rd March 2007, 10:10 AM   #9
Tyimo is offline Tyimo  Hungary
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Thanks Grey!

We will try it.

Tyimo
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