Abomination! or Painting a Mustache on the Mona Lisa meets the Island of Dr. Moreau - Page 20 - diyAudio
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Old 31st December 2008, 08:32 PM   #191
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Default Re: re post 182

Quote:
Originally posted by ostripper

.. it is your widlar CM that will increase OLG...
Hi OS,
Look again, that isn't a CM. It's 2 CCS only different from the Abomination in that it uses a T instead of an LED for bias.

Quote:
Originally posted by atiq19


some real amp testing can bring more practical results.
Hi atiq19,
Good tip for the simulator.
Such compensation is easy to tack on after the board is done if I find that it is needed.
If this is anything like the Abomination, it won't be needed - I have tested that amp already with capacitive loads.

Fixed up the schematic:

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Old 31st December 2008, 08:52 PM   #192
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Quote:
Originally posted by KLe
Nice John ... as you would say, keep it simple

Hi KL,
Me being a minimalist again


This only uses two more transistors (total=28).
The question is, is it a better amp? I have massively improved PSR, but below a certain value, this won't be a discernible improvement (IMO).
I have about the same 1k THD. Spectrum of the harmonics I don't trust, but both amps simmed show 2nd stronger than 3rd, with not much up higher. I haven't tested 20k yet.

Loop gain:

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Picture perfect.
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Old 1st January 2009, 03:52 AM   #193
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As I said , it's the cascoded VAS that makes the grade..
I had the exact same plot at 1.1mhz UGwith 47pf Cdom/same VAS..
(63 db at 100hz /-100 phase- UG intersection)
Click the image to open in full size.
[that is with 68pf]

Much better than "standard" blameless or even symasym
topology(simulation). The question remains, How will a cascoded VAS sound ,(maybe you could tell me as you have heard it..)

The french article earlier in my post and the "magic resistor"
definitely changes the distortion content (stupid low already)
increasing H2. you might want to include pads for the resistor
in case my hunch is right.
Os
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Old 1st January 2009, 01:42 PM   #194
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Quote:
Originally posted by ostripper
As I said , it's the cascoded VAS that makes the grade..
I had the exact same plot at 1.1mhz UGwith 47pf Cdom/same VAS..

How will a cascoded VAS sound ,(maybe you could tell me as you have heard it..)

Feeling a wee bit queasy this morn'...

That's a dead ringer for this amp! There is magic in these designs, for sure.

As for the sound, well I listened to the Abomination and it sounds very good, very smooth in the mid/high. There seemed to be a slight difference to my Patchwork, but that may have been imagined.
Personally I don't think there would be an audible difference as long as it it working as it should.
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Old 13th January 2009, 09:27 PM   #195
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Hey John

Any more Bain/Abomination changes

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Old 14th January 2009, 03:29 AM   #196
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Hi KL,
Bain is on the shelf until I get the time and motivation to attack it again. I am encouraged by the recent progress though and think it can be a worthwhile amp to develop.

I'm busy with projects I started and didn't finish - one of which is a phono preamp. I've made several board changes and etched several boards in an attempt to find the most quite one.
Also started and halfway finished a pair of small speakers for my office that will play my new K10A. These have a solid wood baffle with a waveguide carved in for the tweeters. Here's how they look. A bit rough still in this pic, but they have been sanded and look a lot better now:

Click the image to open in full size.

I'm a sucker for punishment.
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Old 11th April 2009, 03:21 PM   #197
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MJL21193,
correct application-without explanation.
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Old 11th April 2009, 09:33 PM   #198
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Quote:
Originally posted by Lumba Ogir
MJL21193,
correct application-without explanation.

It's not clear to me how this is an improvement. Your change lowers the current through U21, U22. Too low and reducing R7, R8 will not be enough. I end up with insufficient current through the VAS.
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Old 12th April 2009, 12:54 AM   #199
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MJL21193,
it is the configuration of principle, please choose your operating points.
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Old 12th April 2009, 04:46 AM   #200
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Lumba,
I'll work on it.
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