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Old 30th November 2012, 12:15 PM   #91
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Originally Posted by HumNSmoke View Post
Shorting the so called "cold" pin3 to ground permanently make me afraid to kill the output OP-amp. Should I instead leave the pin3 unconnected?
Yes, you can. (No risk to short circuit neither: there is a 60 Ohm serial resistance )
But the best would be, or modify the DCX to bypass the output Opamp, or to charge the - output by the same resistance than the one of your input amp (31K).
nb: The audio stages of the DCX2496 are not top of the world.
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Old 30th November 2012, 01:05 PM   #92
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...or to charge the - output by the same resistance than the one of your input amp (31K):
What an elegant idea man, great, this makes the difference between the centurion and the optione . The charges will find room in XLRs until I decide to use balanced everywhere, because with all these stereo boxes it is difficult to remove all ground loops without using tweaked dedicated cables, ground here/not here.
BTW, no more need the 100/200Ω from ground(s) to earth to mute the hum.
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nb: The audio stages of the DCX2496 are not top of the world.
Yes, I read this... but shall I ear? I'll wait for the warranty to expire before I modify it

Now next step, choosing amps for 8Ω/8Ω meddle/treble. Any advise about the power for them, suited with the power of Crescendo for bass (8Ω too)? (knowing I can't afford high-end and my -40dB 50 years old ears half broken by too many hard-rock concerts ... but I also must think to youngest at home).
What about this 50W or 100W or just LM3886 ?
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Old 30th November 2012, 01:39 PM   #93
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Originally Posted by HumNSmoke View Post
Yes, I read this... but shall I ear?
If you run very dynamic and detailed speakers; OH YEAH !
Quote:
Originally Posted by HumNSmoke View Post
Now next step, choosing amps for 8Ω/8Ω meddle/treble. Any advise about the power for them, suited with the power of Crescendo for bass (8Ω too)? (knowing I can't afford high-end and my -40dB 50 years old ears half broken by too many hard-rock concerts ... but I also must think to youngest at home).
What about this 50W or 100W or just LM3886 ?
Do yourself a favor: Run a Good (and cheap) Class D amp for basses (ex: Ncore400). And reserve your crescendo for trebles :-)
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Old 30th November 2012, 05:25 PM   #94
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Oooch, seductive for sure! It seems things changed since the 80's. Is this new class D thing the top nowadays? At least it seems to be have high Quality/Weight/Temperature/Consumption/Price ratio.

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Old 30th November 2012, 05:39 PM   #95
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Is this new class D thing the top nowadays?
Lot of people say that.
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Old 30th November 2012, 07:17 PM   #96
wahab is offline wahab  Algeria
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I was not talking about HD, but TIM
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TID (aka TIM) was proposed by Matti Otala in 1972, and the basic concept is 100% true. Unfortunately for the proponents of TIM/TID, it doesn't actually happen with real music in any reasonably competent amplifier (which is almost all modern amps, including IC types).
Myths in Audio
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Old 1st December 2012, 05:06 AM   #97
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I'm not an audiophile (read my signature).
I discovered the Otala's article near the 80s, while we where studying effects of speed on servos since 1970, and produced at this time an amp with one of the first 10Mhz Epitaxial power transistor for that reason.
I don't believe in words, or magazine papers. I believe in what i do have experienced and measured.
But, you are not about bring back this boring CFB/VFB controversy on this thread ? Do you ?
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Old 1st December 2012, 06:22 AM   #98
wahab is offline wahab  Algeria
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My point is that unless an amp enter slew rate limitation there will
be no other conditions under wich slew induced distorsion (SID/TIM
or in french "distorsion d intermodulation transitoire) could be measured.

As for an eventual CFB/VFB polemic about it, please no more prejudices
and other "proces d intentions" wich have no relevance with what i did
write earlier in this thread.....
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Old 1st December 2012, 07:38 AM   #99
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My point is that unless an amp enter slew rate limitation there will be no other conditions under wich slew induced distorsion (SID/TIM
or in french "distorsion d intermodulation transitoire) could be measured.
My point was: Audible distortions (harmonic, intermodulation, phase modulation), in a non linear open loop amplifier -they are all because components non linearities- depend greatly on the ratio signal slew rate / amp slewrate in a closed loop.
It is some kind a exponential curve. So, faster the transmission in the loop, better it is.
There is no point where you can say: "that's enough".
You can verify this, comparing input/output of musical signals in any amplifying device with a very fast comparator. (i mean substracting the input signal from the output one). It is enough to look and listen to the results to be aware of this. We spend weeks on this kind of evaluations.
May-we stop arguing on this subject, far from the Crescendo point, it was just to explain why i preferred to use less miller cap as possible?
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Old 8th January 2013, 07:30 PM   #100
paul301 is offline paul301  Zimbabwe
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Thanks Christophe for a great update of the Crescendo. Results are very impressive and an exciting sound is produced.
To everyone thinking about doing this update be most careful to follow the details very carefully!
Thanks again, Paul
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