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Old 19th November 2007, 03:33 PM   #211
KSTR is offline KSTR  Germany
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I have to correct myself... EU mains voltage is 230V+-10% from 2008, not 230V+-15% (but I remember this value to be used as a design goal). +-10% is still a lot, 207V...253V. And it's RMS, not peak, but the latter is dominant for the PSU, at least under low load conditions (hence not much of a problem with class A).

It all comes from the EU-wide change to canonical 400V tri-phase... which poses a lot of problems with smaller tri-phase motors designed for 380V. These are likely to overheat and burn, because they are designed to run near saturation.

There is funny stuff in jacco's second link:
"The mains voltage has a surprising effect on the performance of a CD player. The motor speed is voltage controlled not frequency controlled with a crystal reference as most people would expect.

Even though the motor supply voltage is regulated, the mains voltage does affect it, making it play slightly faster or slower.

The effect on the music is quite large, making it sound either fast and exciting or slow and relaxed. I discovered this whilst experimenting to find out why a ‘Pandora’ isolating transformer, that was claimed to improve CD sound quality, did affect the sound. I discovered that the ‘Pandora’ was simply increasing the mains voltage by 24 volts, hence increasing the play speed and making the sound appear more ‘exciting’."


Oouuchh! is all I can say to that "expert statement"...


Back to Topic, and back to TickTock's question:
The "X-factor" is not the relevant aspect in the context of the power supply... rather it's the fact that this will be a bridged class A output stage. Only these draw constant current from the supply and need the PSU ground connection only as a reference point, with no load current flowing. In contrast, a non-bridged stage also draws a constant current, but only in an overall sense, not on the individual supply rails (at least these see only true reflected load currents, not the nasty half-wave rectified load currents as in class AB). Needless to say I'm a big fan of bridged class A...

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Old 19th November 2007, 04:01 PM   #212
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I was thinking about building the output stage with Lu1014Ds cascoded with the IRFP240s. Im my little world with limited understanding, this should be what dreams are made of...

SandMarc
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Old 19th November 2007, 05:58 PM   #213
EUVL is offline EUVL  Europe
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> I was thinking about building the output stage with Lu1014Ds cascoded with the IRFP240s.

LU1014 cascoded needs 0V on the gate when used with a source resistor of about 0.68 ohm. IRFP240 as used in the A-J schematics has a corresponding gate voltage of about 4.5V. Not really a drop-in, shall we say ?


Patrick
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Old 20th November 2007, 07:00 AM   #214
Lucas_G is offline Lucas_G  Netherlands
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Default Alep 2 with Aleph J combined?

Hi J-builders,

Maybe this has been discussed somewhere, but i could not find it.
Has anyone designed an Aleph 2 with the Aleph J input?

I would like the 100 Watt power of the Aleph 2, but I would also like the improved sonics of the Aleph J. How can this be done?

Regards,

Lucas
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Old 20th November 2007, 07:24 AM   #215
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Quote:
Originally posted by Lucas_G
How can this be done?
Not, unless you're willing to skip the 2-stage feature.
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Old 20th November 2007, 07:41 AM   #216
Lucas_G is offline Lucas_G  Netherlands
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Quote:
Originally posted by jacco vermeulen


Not, unless you're willing to skip the 2-stage feature.

Understood.
But can one build a more powerful version (60 to 100 Watt)?
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Old 20th November 2007, 07:43 AM   #217
Zen Mod is offline Zen Mod  Serbia
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Default Re: Alep 2 with Aleph J combined?

Quote:
Originally posted by Lucas_G
Hi J-builders,

Maybe this has been discussed somewhere, but i could not find it.
Has anyone designed an Aleph 2 with the Aleph J input?

I would like the 100 Watt power of the Aleph 2, but I would also like the improved sonics of the Aleph J. How can this be done?

Regards,

Lucas

Quote:
Originally posted by jacco vermeulen


Not, unless you're willing to skip the 2-stage feature.

that means in Jaccovitty slang ............ that you need cascodes on jfet's bottom ( to save them of excessive voltage) and nice follower stage to achieve enough current for driving all these hungry gates in output

hmmmm - Papa will probably call that follower just 1/2 of stage
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Old 20th November 2007, 07:46 AM   #218
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> I was thinking about building the output stage with Lu1014Ds cascoded with the IRFP240s.

LU1014 cascoded needs 0V on the gate when used with a source resistor of about 0.68 ohm. IRFP240 as used in the A-J schematics has a corresponding gate voltage of about 4.5V. Not really a drop-in, shall we say ? <

Of course not. ( Not that limited understanding ). By posting I hoped that someone would maybe come up with a clever way around it. Coupling caps or whatever.

SandMarc
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Old 20th November 2007, 07:55 AM   #219
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Quote:
Originally posted by sandmarc
..............

Of course not. ( Not that limited understanding ). By posting I hoped that someone would maybe come up with a clever way around it. Coupling caps or whatever.

SandMarc

with caps is hard to maintain DC offset

I'll try to be smart....... but someone will be faster, certainly........

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Old 20th November 2007, 11:01 AM   #220
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> but someone will be faster, certainly........

One possible solution is, for example, you can put a 4V5 10W Zener Diode below the source resistor.

Not that this is the best solution with the least distortion......




Oh, another one :

Hang a 4mA constant current diode (e.g. J511) from each of the drains of the JFET diff pair to 10V below the negative rail.

The rest I should leave as mental jogging exercises.


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