Abomination! or Painting a Mustache on the Mona Lisa meets the Island of Dr. Moreau - Page 19 - diyAudio
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Old 31st December 2008, 12:41 PM   #181
AndrewT is online now AndrewT  Scotland
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no emitter load on the U1&5 drivers.
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regards Andrew T.
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Old 31st December 2008, 12:48 PM   #182
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Default Re: Re post 174

Quote:
Originally posted by atiq19
any reason for not using thermal trak? tripple emitter follower instead of CFP?
Hi,
I have another end use for this amp and it's better (for me) if it uses regular devices. The triple EF shows slightly better THD performance (here) and is more stable. Also, to change it up

Quote:
Originally posted by atiq19
how about bob cordell thermal-trak bias spreader and T-output? u need to modify the upper and lower CCS for VAS connection.

you could add mosfet flavour by swapping bjt driver over with low Ciss MOSFET.
The bias solution I used in the Abomination works splendidly, so I can't see a reason to change it, but thanks for pointing out the circuit - I may use it someday.

I'm not ready for FETs yet. Maybe sometime in the future...

Quote:
Originally posted by atiq19
Despite the fact that the amp is absolutely stable in simulator, I would still like to have a small phase lead compensation cap (1-3pf) from collector of VAS to fb loop.....

I haven't looked at the gain and such in this one, but the Abomination didn't need any such compensation.
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Old 31st December 2008, 12:49 PM   #183
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Quote:
The CFP input was in the last version of this, several posts ago. I haven't examined the gain yet
I did CFP's and noticed very little improvement.. it is your
widlar CM that will increase OLG... Strange, when I did your
amp thats what I did as well as use the zetex killer Hfe
trannies to get 70+ out of it (abomination)

It looks like your amp is a hybrid of FA2 and 3 (cascode)
Still you have a "lavardin amp" as well as me...
Read this ....http://peufeu.free.fr/audio/memory/memory-5-vas.html

All about cascoded VAS's (fast, fast)
OS
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Old 31st December 2008, 12:50 PM   #184
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Quote:
The bias solution I used in the Abomination works splendidly, so I can't see a reason to change it
With a triple you might have to..

Os
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Old 31st December 2008, 12:51 PM   #185
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Quote:
Originally posted by AndrewT
no emitter load on the U1&5 drivers.

HNY Andrew,
This darlington configuration will not work? I wanted to play with an R between, E to B.
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Old 31st December 2008, 01:01 PM   #186
atiq19 is online now atiq19  United Kingdom
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Default re post 182

you can check necessity of such compensation on your simulator by parallelling a ,say, 2.2uf capacitor at the output..

however, a single parallel cap does not necessarily represent a real life complex x-over network loudpeakers variable impedance.

some real amp testing can bring more practical results.
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Old 31st December 2008, 01:24 PM   #187
atiq19 is online now atiq19  United Kingdom
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Default some tuby fun with abomination

in the spirit of 2009,

how about changing fb loop with some twist of 6GM8 (low voltage ) triode...

in this way the amp could be switched from pp to se.....2nd harmonic dominant..

since 6gm8 is low voltage, you don't think about HV.. you may have to shield 6GM8 on actual pcb..


cheers
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Old 31st December 2008, 01:26 PM   #188
atiq19 is online now atiq19  United Kingdom
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Default more tuby fun

the previous one curtesy JRB

this one Smoking Amp,
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Old 31st December 2008, 01:27 PM   #189
atiq19 is online now atiq19  United Kingdom
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Default oops

my mistake..
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Old 31st December 2008, 05:08 PM   #190
KLe is offline KLe  Australia
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Nice John ... as you would say, keep it simple

HNY
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