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Dynamic Bias - Active Bias - Automatic/Self biased - Overview wanted
Dynamic Bias - Active Bias - Automatic/Self biased - Overview wanted
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Old 25th July 2010, 12:09 PM   #11
tiefbassuebertr is offline tiefbassuebertr  Germany
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this approach from Marantz looks a bit like EDWIN from Elektuur
http://www.diyaudio.com/forums/solid...970-may-2.html

MCU+LDR is one of several methods (in use e. g. by Krell) - but look at post #6: this are solutions without MCU and I want to know commercial amps, where this IC's are inside.
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Old 5th May 2011, 08:42 PM   #12
tiefbassuebertr is offline tiefbassuebertr  Germany
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an additional bias servo approach, that looks very interesting
http://www.diyaudio.com/forums/solid...ml#post2562916
http://www.freepatentsonline.com/5055797.pdf
and post #40 about
http://www.diyaudio.com/forums/solid...o-power-4.html
but obviously there are very few adjustment free commercial amps; I am still looking for such audio amplifiers.

P.S.: I don't like power amp topologies like output stage (Sanken's approach) from Marantz SR-5200 (go to post #8). In case of service Sanken's output power devices is in several years a very "hard to find" part. So it is necessary, to modify the topology down to the good known Vbe multiplier circuit for using usual BjT's. Are the embedded diodes on the power BjT chip so a great advantage ??
I don't think so, otherwise the embedded diodes there must actually be inside by most power BjT versions.

Last edited by tiefbassuebertr; 5th May 2011 at 09:05 PM.
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Old 10th July 2012, 09:37 AM   #13
tiefbassuebertr is offline tiefbassuebertr  Germany
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Here is an approach, that I do find by one model: Sony's TA-N 902 - go to
Sony TA-N902 on thevintageknob.org
and for Service Manual:
SONY TA-N902 Service Manual free download, schematics, eeprom, repair info for electronics
associated patent paper:
Patent US4439743 - Biasing circuit for power amplifier - Google Patents
- found by post #98 about
Yamaha's Hyperbolic Conversion Amplification (HCA) Circuit

other approaches with the same goal:
http://www.diyaudio.com/forums/solid...d-revival.html
http://www.diyaudio.com/forums/solid...on-1975-a.html
adaptive bias theory

I am still looking for currently available commercial audio amplifier devices or modules without the need of quiescent current adjust for the output push-pull power buffer (except Class-D).

Last edited by tiefbassuebertr; 10th July 2012 at 09:46 AM.
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Old 11th July 2012, 03:08 PM   #14
JamesBrennan4 is offline JamesBrennan4  United States
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I have Meridian 555 and 556 amplifiers. They do not have any bias adjustment. They use error correction on output stage, thus allowing the output stage to be biased low, but still obtaining low output stage distortion.
Additional benefit is low idle power. Unfortunately, I have not been able to obtain schematics or even detailed description of actual circuits.
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Old 29th July 2012, 01:18 PM   #15
tiefbassuebertr is offline tiefbassuebertr  Germany
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have anybody tested this topology?
http://home.tiscali.nl/data.odyssey/AutoBias.html
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Old 29th July 2012, 01:58 PM   #16
FdW is offline FdW  Netherlands
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Dynamic Bias - Active Bias - Automatic/Self biased - Overview wanted
At the same site you can find http://home.tiscali.nl/data.odyssey/...wLoopGevel.pdf
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Old 29th July 2012, 04:03 PM   #17
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Dynamic Bias - Active Bias - Automatic/Self biased - Overview wanted
Nelson is having patent on opto bias
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Old 25th December 2017, 10:30 PM   #18
tiefbassuebertr is offline tiefbassuebertr  Germany
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Quote:
Originally Posted by tiefbassuebertr View Post
commercial products (brand and model number), that use adjust-free Class AB power amp sections still wanted (e.g. with the help of TDA7250/LT1166)
any news?
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Old 26th December 2017, 02:24 AM   #19
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Dynamic Bias - Active Bias - Automatic/Self biased - Overview wanted
Elvee's Circlophone:

http://www.diyaudio.com/forums/attac...irclophone-gif

Click the image to open in full size.

inverted JFET of same amp by Piersma:

Inverted J-FET Circlophone Builders thread

Click the image to open in full size.

I have built the latter, and it sounds very good.
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Old 13th April 2018, 07:52 PM   #20
tiefbassuebertr is offline tiefbassuebertr  Germany
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Default Linn LK2: Autobias or pre-adjust Bias ?

Quote:
Originally Posted by tiefbassuebertr View Post
have anybody tested this topology?
http://home.tiscali.nl/data.odyssey/AutoBias.html
The Link is death but available under
Auto Bias
Who can upload this AES paper:
AES E-Library >> THE AUTOBIAS AMPLIFIER: A New Topology for Automatically Biased Audio Amplifiers Using Power MOSFETs
In the attachment the BIAS circuit of Linn's LK-2 and LK2-80.
Is it an autobias or not?
Thank you for an advice.
Attached Files
File Type: pdf C_tmp_Linn LK2, LK2-80_ckt bias.pdf (9.7 KB, 28 views)
File Type: pdf Linn LK260.pdf (71.6 KB, 26 views)
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