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Old 3rd February 2008, 08:31 PM   #1981
cviller is offline cviller  Denmark
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Quote:
Originally posted by Andrzej Sochon


I understand what you mean; but in my opinion 100u and 22n does not provide an ac path from out to signal in gnd. Capacitors added by me are between In GND and internal +/- DC sub-rails, creating additional filter.
a.

I'm afraid you can't think of them as dc stable sub-rails - it is a trick by NP to make life a little easier on the jfets. If you don't end up with a ground loop, I think you get 6db attenuation with this configuration, the output decoupling however should be perfectly fine!
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Old 3rd February 2008, 09:45 PM   #1982
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Quote:
Originally posted by cviller
I'm afraid you can't think of them as dc stable sub-rails - it is a trick by NP to make life a little easier on the jfets. If you don't end up with a ground loop, I think you get 6db attenuation with this configuration, the output decoupling however should be perfectly fine!

I am not sure if I understand you well, Cviler, but I do not observe any attenuation with my configuration. More: I have a feeling that all details of the stage are more clear. Maybe another NP trick. Or something wrong with my ears or with my "single grey matt between ears", as my Wife says...
Time to sleep...
a.
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Old 4th February 2008, 06:00 AM   #1983
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Quote:
Originally posted by Andrzej Sochon


. . . I have a feeling that all details of the stage are more clear.

How big difference from the original? Tks.



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Old 4th February 2008, 06:35 AM   #1984
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Default Extra rail caps for F4

Hi Andrzej,
Try adding a small resistor [0.1 - 0.3 ohm] in series with the 22 and 47nF caps - I generally use [100nF + 0.15 - 0.2R] as bipass for 220 - 470uF electros. Big surprise!!
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Old 4th February 2008, 08:34 AM   #1985
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Quote:
Originally posted by Babowana
How big difference from the original? Tks.
Hi Babowana,
Difficult to explain, I have language problems, sorry.
SOZ was my f4 predecessor, great sound, but catching details of an acoustic stage was difficult for me. Before listening I always precisely checked super symmetry positions of speakers in the room. Then I sat at the triangle corner. Many times during listening I moved myself slightly to front or back to find the best stage symmetry and details. Tiring kind of listening.

Now, with f4, listening is much easier and gives much more pleasure. Super symmetrical positioning of speakers is not the most important thing, moving ears forward and back brings no significant improvement.

Some mentioned capacitors more and – a new discovery: I can seat not exactly on symmetry line. Stage is not dramatically shifted to the right side if I am one meter to the right from symmetry line - Acoustic stage remains natural. In other words the listening space transformed from triangle to an isosceles trapezium. Listener (listeners) are on the shorter segment of trapezium.

What more: now I have better balance between medium and hi frequency. Before adding capacitors I had to much medium tones. But maybe this is a result of warmed up elements.
I do not have pre-amp. My f4 are driven directly from DAC balanced outputs.
a.
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Old 4th February 2008, 08:40 AM   #1986
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Default Re: Extra rail caps for F4

Quote:
Originally posted by jameshillj
Hi Andrzej, Try adding a small resistor [0.1 - 0.3 ohm] in series with the 22 and 47nF caps - I generally use [100nF + 0.15 - 0.2R] as bipass for 220 - 470uF electros. Big surprise!!
Hi James,
What do you mean "Big surprise"?
Do you use the same concept, I mean additional capacitors on input?
I am afraid my f4 are difficult to modify - I mean access to the parts, to many screws to release...
Best Regards,
andrzej
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Old 4th February 2008, 08:48 AM   #1987
Maousse is offline Maousse  France
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Default Re: Extra rail caps for F4

Quote:
Originally posted by jameshillj
Hi Andrzej,
Try adding a small resistor [0.1 - 0.3 ohm] in series with the 22 and 47nF caps - I generally use [100nF + 0.15 - 0.2R] as bipass for 220 - 470uF electros. Big surprise!!
That's snubbers
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Old 4th February 2008, 11:57 AM   #1988
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Yeah Maousse,
"snubbers" - sort of.
I think it's technically a "resonance control" device - lots of theory about these things on the "Capacitor Bipass" thread.

Rather pleased at improvement in overall clarity and base detail particularly with the B.Gates - rather surprised, too.
Rather useful little thing, this.


Andrzej,
I just added some 220uF (and the bipass R-C, as usual) from point R5/R7 to Gnd (and P2/R6, too) for some "rail isolation" from power Fet modulation - pretty standard procedure and seems to work okay - can't see why it would present any problems - not sure about your Signal Gnd point, tho.....

There's something about the D3,4 diodes that look "naked" - and those TL431s are sometimes noisy, no?

The simple R-C network has been added to caps C1,2 (B.Gate N),3,4 (1000uF Nichi KZs)and 5,6 (Rubi ZL) by simply adding them directly across the electro cap pins underneath the pcb - easier with SMD resistors, tho.

What speakers are you using, and room Q?

....... Hope this is of assistance.
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Old 4th February 2008, 12:16 PM   #1989
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Quote:
Originally posted by Andrzej Sochon


. . .

Some mentioned capacitors more and ?a new discovery: I can seat not exactly on symmetry line. Stage is not dramatically shifted to the right side if I am one meter to the right from symmetry line - Acoustic stage remains natural. In other words the listening space transformed from triangle to an isosceles trapezium. Listener (listeners) are on the shorter segment of trapezium.

What more: now I have better balance between medium and hi frequency. Before adding capacitors I had to much medium tones. But maybe this is a result of warmed up elements.
I do not have pre-amp. My f4 are driven directly from DAC balanced outputs.

Thanks for the very interesting info.
When I saw your additional caps first, I thought them just as
a simple reinforcement for cleaner dc-supply. But, they seem to
be doing more work than expected.

I also try to find the sweet listening spot, moving my seat around
as you do, for serious listening. Your variation is quite simple and
seems to be worth trying . . .

No pre? If you like tube sound, I would like to inform you that
the good parts of tube pres are well powered by F4 . . .



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Old 4th February 2008, 02:20 PM   #1990
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Quote:
Originally posted by jameshillj
Y Andrzej, I just added some 220uF (and the bipass R-C, as usual) from point R5/R7 to Gnd (and P2/R6, too) for some "rail isolation" from power Fet modulation - pretty standard procedure and seems to work okay - can't see why it would present any problems - not sure about your Signal Gnd point, tho.....

There's something about the D3,4 diodes that look "naked" - and those TL431s are sometimes noisy, no?

The simple R-C network has been added to caps C1,2 (B.Gate N),3,4 (1000uF Nichi KZs)and 5,6 (Rubi ZL) by simply adding them directly across the electro cap pins underneath the pcb - easier with SMD resistors, tho.

What speakers are you using, and room Q?

Hi JH,
You are right about my Signal Gnd point, maybe better is to use PSU Gnd point instead. But at the moment it is difficult to modify.

I do not have any ideas about D3,4 diodes, and TL431’s. I do not observe noise, maybe future preamp will unveil noisy points of my f4. Or maybe my ears are to old.

I also had an idea to add small parallel caps to C1,2, but I did not, just because of lack of patience. I have to buy BG capacitors and compare with present accidental Philips.

What about C3,4 – why do you add RC network here – does it affect sound? I think R24C4 and R25C3 are important at power ON/OFF temporary states.

Speakers: Suspense’93 (Manfred Zoller project, kits of Focal speakers, year 1993), 8Ohms,approx. 91 dB. I made housings according to the Mr. Zoller design. In spite of no preamps sound level is quite big. Each speaker consists of two bass speakers, one mid and one tweeter, bi-wired.

Room Q is approx 50 cubic meters.

Best Regards,
a.
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