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Old 28th July 2002, 06:41 AM   #21
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Thanks a lot.
It doesnt look bad at all.
A little complicated but looks very cool.
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Old 31st July 2002, 04:50 PM   #22
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Reading this post I saw that it is not complete.

After looking at the Nelson Pass DAC analog output, I thought maybe I can use it after all. I would like to know if it would work if I ground one input to ground and use this analog output as balanced ?
About the volume resistor between the two parts maybe I can use one constant resistor for a preset gain.

What is your opinion on this ?
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Old 1st August 2002, 08:32 AM   #23
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Default but there is global feedback

Looking at the very first post in this thread, I'd say that the schematic seems to use a global feedback setting the gain to 11. The feedback resistors are not shown in the upper half of the picture, but in the lower half where the servo circuit is sketched, there is a 10 k resistor from output to I- and from there to ground. I have not calculated the open loop gain, but as Nelson points out, there probably is not much...

Having the DC servo act on the tail current rather than on one of the audio inputs seems kind of appealing. On the other hand, symmetry and hence distortion performance are a function of this tail current. Let's hope it does not introduce any kind of strange modulation...
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Old 1st August 2002, 09:48 AM   #24
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Default jFET etc

Hi,

I saw in the schematic that the input current is specified as +/-1.2mA. I'm not sure, but should that not be 2.4mA single sided, that is the current varies from 0 to +2.4mA?

If that is the case, the input cap should be removed, otherwise it will charge up to a DC level that will be to high.

Just my 2eurocts worth..

Jan Didden
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Old 1st August 2002, 10:01 AM   #25
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Which of all the schematics are you refering to.
The first, from Nelson Pass or the last ?
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Old 1st August 2002, 10:18 AM   #26
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The one by rickpt of 28-07

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Old 2nd August 2002, 08:24 AM   #27
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Burr-Brown DACs are +/- 1.2 mA output. Philips DACs are what you might be thinking of.

Jocko
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Old 2nd August 2002, 10:52 AM   #28
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Default jFET etc

Right, thanks.

Jan Didden
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Old 20th November 2003, 06:12 AM   #29
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I would be interested in some discussion as to suggestions to tweak or improve this circuit
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