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Old 15th October 2008, 06:16 AM   #761
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Old 15th October 2008, 10:17 AM   #762
ABO is offline ABO  Netherlands
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Hi Salas,

Are you saying that a 330 ohm Kiwame sounds more dynamic than normal resistor of 220 ohm? I started with normal 1000 ohm, then tried 50 ohm Caddock MK132 and then no resistor at all. In all cases the dynamics were correlated with resistor value, i.e. no resistor sounds better than 50 ohm Caddock.

As for the gate resistor, I have found before that higher value resistor tend to loose detail. In another project I replaced a 1k Riken with 120 ohm normal resistor. And guess what, the cheap resistor sounded notably better (more detail and presence).

Of course, any oscillations introduced by modding the circuit could easily offset the benefits.
Is there any easy way to check (measure) if there are any parasitic oscillation present in the circuit? Such as measuring supply current for instance?
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Old 15th October 2008, 11:11 AM   #763
Salas is offline Salas  Greece
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It may depend on what kind of ''normal'' metal film resistors we used or our interconnects or how easy our load was. But you compared to 20 times lower good quality, and to nothing. So I can't draw conclusions easily. Yes my 330 Kiwame sounded better than 220 off the shelf Chinese something.

For input, your 1k to 120 comparison (in another circuit) is in the order of 10 so the value difference would normally have prevailed.

But as I wrote earlier, if B1 is to stay put in a given system, then its better to practice preference. The lower it tolerates, the better. And better be best quality if any.

Oscillation you will see if happening, on high frequency square waves with a generator and a scope. 10, 20, 50, 100kHz. Little peaks and ringing at the edges.
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Old 15th October 2008, 11:42 AM   #764
flg is offline flg  United States
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Default Re: Re: What?

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Originally posted by Derekva
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Old 15th October 2008, 06:55 PM   #765
mtj is offline mtj  United States
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This smells like a marketing move. Limit the number of Xbox's first released into the market to drive up hype. Ha

Just kidding. I will switch from looking twice a day to four times a day. How many boards were in the first run?

MJ
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Old 15th October 2008, 07:04 PM   #766
Zen Mod is offline Zen Mod  Serbia
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Default Repeating Important Info For All Spoiled Kids

Papa sez :

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We will continue to take orders in the meantime and ship those boards/fets when they arrive.
edit :

don't worry - I already order my 347 sets , so you'll have your set around NYE 2010 .

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Old 15th October 2008, 07:58 PM   #767
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Old 15th October 2008, 08:02 PM   #768
ABO is offline ABO  Netherlands
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Default would this work?

I'm not sure if this would be considered off topic. If so, please ignore my question.

I was thinking of the problem with the low psrr of the White jfet topology. It seems that the problem is that the current from the upper jfet is converted into a voltage that is referenced to the positive supply voltage. The lower jfet, which is referenced to the negative supply, is driven with this voltage. Therefore, any noise between these supplies is amplified by the circuit.

A simple solution would be if a current mirror was placed in the drain of the upper fet. The secondary side or the mirror could have a resistor to the negative supply (I am assuming symmetric supplies). This voltage would be thus referenced to the negative supply, and would therefore have far better supply rejection.

If that would work I'm not sure. In any case the circuit would be not-so-simple anymore as it would need two more transistors and some resistances. On the other hand, it could perhaps be possible to loose the capacitive coupling altogether as it might be possible to use the current to directly drive the gate of the lower jfet.

Any thoughts?

-edit: it occurred to me that my idea would introduce a phase inversion and hence positive feedback. Will have to think about it some more.
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Old 15th October 2008, 08:17 PM   #769
Zen Mod is offline Zen Mod  Serbia
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Default Re: would this work?

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Any thoughts?

is this good - for single rail variant ?

in fact - I think - good enough even for dual rail thingie
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Old 15th October 2008, 08:32 PM   #770
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Default Re: Re: would this work?

Quote:
Originally posted by Zen Mod



is this good - for single rail variant ?

in fact - I think - good enough even for dual rail thingie

Your drawing skills always amaze me... Click the image to open in full size.
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