Crescendo Millenium amplifier (ELEKTOR magazine ¹4 2001 p.36-45)? - diyAudio
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Old 25th January 2002, 12:45 AM   #1
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Question Crescendo Millenium amplifier (ELEKTOR magazine ¹4 2001 p.36-45)?

What judgement on the amplifier, the scheme which one was published in the " ELEKTOR ELECTRONICS" ¹4 2001 p36-45?
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Old 28th January 2002, 11:46 AM   #2
Eccu is offline Eccu  Finland
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And I have questions about operating voltage of Cresendo ME.
In schematic recommend 45-50 VDC (about 35 VAC) so can I use lower or higher voltages?
I can get transformers with 30 VAC (about 42VDC) or 38 VAC (about 53 VDC).
Which one is better? And do I have make some modifications in schema if I use lower or higher voltages?

Thanks!
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Old 7th February 2002, 09:15 PM   #3
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use the 53 v ones, the amp has SOAR protection
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Old 7th February 2002, 11:59 PM   #4
UrSv is offline UrSv  Sweden
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The 2*38 VAC secondary will give you about 2-4 volts lower than 53 VDC after losses in the rectifier and elsewhere so I would go with the higher voltage. I haven't read the new Elektor Crescendo article (I still have the originals from the 80's though...) and I don't know what the class or bias is but remember that the 38 VAC is UNDER LOAD and that if bias is low the voltage may be a few to maybe even 10 % higher. General rule according to me is to use the highest capacity transformer you can find/afford since the power supply will be tougher and the difference between no load and load voltages decrease with higher capacity (all that internal resistance of secondary windings I think).

/UrSv
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Old 8th February 2002, 06:54 AM   #5
Eccu is offline Eccu  Finland
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I have other question now about Crescendo ME.
Can I replace OP77GP with OP07CP, OP27GP or OP37GP. This OP77GP are used in a sort of Offset compensation.
Because I can´t get this OP77GP.

OP77GP Input Offset Voltage -values typical 50yV(micro V) and Max 100yV.
OP07CP Input Offset Voltage -values typical 60yV and Max 150yV.
OP27GP and OP37GP Input Offset Voltage -values typical 30yV and Max 100yV.




Sorry my very bad English...
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Old 8th February 2002, 10:44 AM   #6
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you can use an LF411CN instead of the OP77

william
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Old 9th February 2002, 12:34 AM   #7
Helix is offline Helix  United Kingdom
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Default Here is mine

Here is my elector amp, oh and the 4 channel pre-amp i made:

Click the image to open in full size.
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it has 4*22,000uF rifa's
500W transformer
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Old 11th February 2002, 10:12 AM   #8
Eccu is offline Eccu  Finland
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are you sure wuffwaff (william) ?
LF411CN have Input Offset Voltage about typical 0,8 mV and Max 2,0 mV when OP77GP have Input Offset Voltage -values typical 50uV(micro V) and Max 100uV?

Nice amp, Helix.

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Old 11th February 2002, 12:22 PM   #9
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eccu,

sure the LF411 was used very often by Elektor for dc-servo´s. A few power amps used them and I still use it in the phono section of my preamp. I changed it for a OP77 in my power amp when I rebuild this.
I think it´s not so important if the power amp has 0,1 or 2mv (or even 20mV) offset as long as it´s below say 50-100mV. The difference in input offset voltage between the op77 and the LF411 will only cause the amp to have 1 or 2 mV more offset.

william
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Old 11th February 2002, 12:56 PM   #10
Eccu is offline Eccu  Finland
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thanks wuffwaff... )

but can I still use OP07 or OP27... ?
OP77 datasheet shows that it is Next generation OP07... so I think that OP07 is better combatible with OP77GP than LF411...

So which one is best choice, because I can get these:
OP07CP costs about 1,6 € (Euros),
OP27GP costs about 3,8 € (Euros) and
LF411CN costs about 1,9 € (Euros).
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