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Old 12th November 2003, 01:09 PM   #11
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Quote:
Originally posted by Andypairo


I'd say it depends on which voltage you are operating it from.
If you use 5V it is probably too high, if you use 7V you can go even higher.
The output current is equal to Ibias (=2*Iref)- IDac , which is sunk by a controlled current sink.
Therefore the "zero" signal current for IDac should be 2.65 mA /2 (if we take the maximum value).

In your case with 2.2 mA Ibias = 4.4 mA and AOR should source about 4.4 - 1.325 = 3.075 mA * 1k = 3.075V

With 2.7 mA you probably saturated the bias current source at 5 mA (its rated maximum), so in this case we should have a theoretical 5- 1.325 = 3.675 V... not corrisponding to the actual value.

Can anyone explain why?

Cheers

Andrea


Ok Andrea ,
I apologie for non-precise numbers regardin my "effective working values".
I must say first that the current source runs in real life at 2.3mA couse the tipical negative voltage of the jfet is not so tipical and it is 0.254volt and not 0.3v.The vref as above mentioned is 2.120 stable with or without music. I measure 3.212 v at one channel output resistor that is something like 985 ohm.
That's all.
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Old 12th November 2003, 01:24 PM   #12
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Stefano,
which Vcc do you use?
5V or higher?

Cheers

Andrea
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Old 12th November 2003, 01:28 PM   #13
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Default Updating

After correct measure of the crucial parameters I update the first post schematic:

If -Your- jfet looks like this for a 2.3mA current the resistor is 130ohm. Otherwise is better measure the jfet vgs for precise current setting.

2.7mA as shown in the first post is just too much

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Old 12th November 2003, 01:34 PM   #14
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Quote:
Originally posted by Andypairo
Stefano,
which Vcc do you use?
5V or higher?

Cheers

Andrea


Aaah! Here we go ! I use now 6.15Volts


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Old 12th November 2003, 01:44 PM   #15
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Well, with 6.15Vcc the "ideal" output voltage (halfway between the minimum and maximum value given by the datasheet) is (6.15-1.2-1.8)/2 +1.8 = 3,375 V, so I think you have a quite perfect idle voltage.

Cheers

Andrea

PS Do you still use your balanced version?
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Old 12th November 2003, 01:59 PM   #16
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Quote:
Do you still use your balanced version?
I like very much balanced operation but I paused it for a while couse I was searching for a different PS to power it and a more detailed and precise sound .Now the ASR is battery powered and I use fets for the TDA 6.15volts. Finally , the current source .

Spectacular result...now I'm ready and back for the balanced version.



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Old 12th November 2003, 02:06 PM   #17
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I'd be very happy if you could post a complete schematic of your setup... mine is halfway between Doede's and the convertus, but I think I'll include the ASR soon, so it will be ready for balanced operation!

BTW should the ASR (and its clock) have its own PS? (I guess so..)

Cheers

Andrea
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Old 12th November 2003, 02:18 PM   #18
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OK Andrea . I'll see what can I do to post a decent schematic of my setup.

Regarding the ASR the answer is yes.Currently I power it with batteries.One for the clock and one for the sinchronizer.
The difference between PS and battery here is noticeable.
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