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Old 8th November 2004, 08:43 PM   #191
MikeB is offline MikeB  Germany
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As a typical classAB-amp is considered as 3stage, the whole output is one stage.
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Old 16th November 2004, 12:43 AM   #192
thanh is offline thanh  Viet Nam
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Ah! john curl used "new vas" before me
Justice for Victims of Agent Orange all of you!
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Old 26th March 2005, 09:31 PM   #193
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I will also here post my Class A preamplifier schematic, with Non feedback, folded back cascode coupling.

I would ask If someone have ideas to optimize the component values, so I can lower distortion or make some sound improvement?

The PSU will be a look a like LCaudio Shunt reg with (PSU will later be +-20V) outputimpedance at 0.01R from DC to 400Khz.

About decoupling, what I decouple the outputstage with 10uF and inputstage with 220nF?

And what if I use a super jung regulator?

Best regards

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Old 29th March 2005, 07:32 AM   #194
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I designed a symmetrical FET input folded cascode line stage preamp for Magnet Technology (Thailand) back in 1994-5, which was very successful in their home market and I believe it later won a TAS 'Golden Ear' award.
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Old 29th March 2005, 08:21 AM   #195
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Wov congratolations with that!

Are you still in the audio industri today?

Do you have any information / schematic for your folded back preamplifier from 94?

May I ask you about my design, anything you think could be better?

Best regards
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Old 1st April 2005, 03:15 AM   #196
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thanks Kimschips.

I have been out of the industry for a few years but am preparing a comeback with a 150W Nch monoblock on spec.

I don't have a copy on hand and would need a schematic drawing pkg to generate it but it was a symmetrical FET input (2SK170/J74 Vgs matched) with complementary TR folded cascode LED biased and EF output in a x10 feedback loop with servo. Simple, nice bits and remote with motorised alps vol. The market loved it.

The amp that won with it started life as a no global feedback company design with comp bip front end, cascode Vas and MJ15003/4 - sounded awful. I tricked it up with comp FET front end applied global feedback and finessed the compensation for much better 20K THD. Absolutely transformed. 2x200W from memory.

regarding your design - I have a great pref for sym FET input with the balance R no CCS. I don't see the need for the 2 stage output. The loadings light enough. My opinion.
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