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Old 5th May 2005, 01:46 AM   #1
kro5998 is offline kro5998  Netherlands
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Default Another crescendo ME question

I just picked up a crescendo ME on ebay. Didn't know it was a crescendo,just bought it for the case.

It has a Thell PSU,transformer and case.Also loudspeaker protection and on delay.

It sounds quite good, better than my Marantz PM17.

Has anyone tried to lower the rail voltagge on these amps?
Mine runs on 56Vdc and i want to lower this to 24Vdc with according higher bias.

Do i need to change resistor values to increase the current through diff pair and driver stage?
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Old 5th May 2005, 02:07 AM   #2
anatech is offline anatech  Canada
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So if you like it, why changew the design ????
-Chris
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Old 5th May 2005, 02:10 AM   #3
kro5998 is offline kro5998  Netherlands
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Default Another Crescendo ME

Hi, I just want to try how it sounds when i run it closer to class A, I was planning to use the case for a class A project but now i am curious how it will sound with more bias.
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Old 5th May 2005, 02:18 AM   #4
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Why not tweak up the existing cct for more.
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Old 5th May 2005, 02:19 AM   #5
anatech is offline anatech  Canada
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Lowering the rails will change all kinds of things. Problem is you would have a different amp. Keep in mind that higher bias current does not mean better sound, depends on the design.

-Chris
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Old 5th May 2005, 03:02 AM   #6
kro5998 is offline kro5998  Netherlands
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Default another crescendo ME

I understand that it might not sound better but you never know before you try.
I had a look at the specs of the output pair (2SJ201/2SK1530) and they can take 12A and dissipate 150W.
They only start to get lineair at 1A so increasing bias might improve the sound.

Kees.
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Old 5th May 2005, 03:18 AM   #7
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I did a commercial MOSFET pwramp using J115/K405's and it had low bias and unmeasurable distortion (on regular test equip).
Bring it on...
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Old 5th May 2005, 10:34 PM   #8
anatech is offline anatech  Canada
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Hi Kees,
Watch your SOA curves for those and derate for temperature. Otherwise, go try it. You could run the drivers and outputs from an external supply to try higher bias levels. Careful not to overdrive the output stage but at least the rest of the circuits will operate as designed.

-Chris
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Old 5th May 2005, 10:44 PM   #9
joensd is offline joensd  Germany
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Hi,
you could just up the bias of your existing crescendo of course.
Drawback is the very high power dissipation.
Maybe you should just try it to hear the difference and temporarily install some fans for extra dissipation.
I want to see your amps!
(post 35)

I tried 1A on my crescendo ME and it didnīt make a difference to me.
(which means nothing of course)

Running it from +-24V would assume quite a few changes so...

greets
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