optical bias, how does it work?

Hardi · 9th September 2004, 05:17 PM

Hi there,

what are the advantages (or disadvantages) of an optical Bias amplifier and how does it work ? (must not be a 100% description)

Is it an (opto coupler) controlled, dynamic bias regulation, that depends on the value of the input (output) Signal ??

thanks
Hardi

Nelson Pass · 9th September 2004, 08:29 PM

In the case of my patent #4,752,745, an optocoupler is used
to transmit the value of the bias current to an earlier stage
which contains the bias circuit. It works very conveniently
to keep the bias at a constant value while isolating the
front end VAS from the output.

anatech · 10th September 2004, 04:16 AM

The way Denon and others use this is to switch to a higher bias state depending on mode. This may be automatic on signal level or by a switch on the front panel. Normally the switch is marked "class A", should be marked "runs too hot". What it does is to put another resistor in parallel with one in the bias circuit. The optocoupler acts as a switch. That's all it does.

Nelson,
I'd like to read how your circuit works, but have no patience for finding patent articals. Is it on your site, or can you email it to me?
Thanks,
-Chris

johnsciolino · 10th September 2004, 09:42 PM

Here you go on that patent

http://patft.uspto.gov/netacgi/nph-P...&RS=4,752,745,

Heres the tool for searching patents next time
http://patft.uspto.gov/netahtml/search-bool.html

anatech · 10th September 2004, 11:28 PM

Thanks John,
Turns out the site does not like Netscape. I had to use IE.
I have some reading to do.
-Chris

Steven · 11th September 2004, 11:10 AM

Or use the European alternative:
http://l2.espacenet.com/espacenet/vi...b&LG=en&DB=EPD
For US patents the number (without commas) should use a US-prefix, e.g. US4752745 instead of 4,752,745. No Alternatiff viewer is required, only Acrobat Reader. Note: this site is not too fast.

Home page: http://gb.espacenet.com/espacenet/gb/en/e_net.htm

Steven

anatech · 11th September 2004, 02:08 PM

Thanks Steven, I'll try that one too.
-Chris

lautsprecherklinik · 14th September 2012, 08:36 PM

Quote:

Originally Posted by Nelson Pass

In the case of my patent #4,752,745, an optocoupler is used
to transmit the value of the bias current to an earlier stage
which contains the bias circuit. It works very conveniently
to keep the bias at a constant value while isolating the
front end VAS from the output.

Hello Mister Pass,

I used a Threshold S 500 first series without optikal bias.
Bias is adjusted.
If the amp is hot 50-55Grad Celsius and the sound level is in living room level ...bass and sound is O.K..
If I get a higher level the bass is going out and the sound would be bad.

What can I do?

Best Regards, Norman

9th September 2004, 05:17 PM	#1
Hardi diyAudio Member Join Date: Feb 2004 Location: Germany	optical bias, how does it work? Hi there, what are the advantages (or disadvantages) of an optical Bias amplifier and how does it work ? (must not be a 100% description) Is it an (opto coupler) controlled, dynamic bias regulation, that depends on the value of the input (output) Signal ?? thanks Hardi

11th September 2004, 11:10 AM	#6
Steven diyAudio Member Join Date: Oct 2003 Location: The Netherlands	Or use the European alternative: http://l2.espacenet.com/espacenet/vi...b&LG=en&DB=EPD For US patents the number (without commas) should use a US-prefix, e.g. US4752745 instead of 4,752,745. No Alternatiff viewer is required, only Acrobat Reader. Note: this site is not too fast. Home page: http://gb.espacenet.com/espacenet/gb/en/e_net.htm Steven __________________ The Analog Art shows no sign of yielding to the Dodo's fate. The emergence and maturation of monolithic processing finesse has perhaps lagged a bit behind the growth of the Binary Business. But whereas digital precision is forever bounded by bits, there is no limit excepting Universal Hiss to the ultimate accuracy and functional variety of simple analog circuits. - Barry Gilbert, 1973

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9th September 2004, 08:29 PM	#2
Nelson Pass The one and only Join Date: Mar 2001	In the case of my patent #4,752,745, an optocoupler is used to transmit the value of the bias current to an earlier stage which contains the bias circuit. It works very conveniently to keep the bias at a constant value while isolating the front end VAS from the output.

10th September 2004, 04:16 AM	#3
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	The way Denon and others use this is to switch to a higher bias state depending on mode. This may be automatic on signal level or by a switch on the front panel. Normally the switch is marked "class A", should be marked "runs too hot". What it does is to put another resistor in parallel with one in the bias circuit. The optocoupler acts as a switch. That's all it does. Nelson, I'd like to read how your circuit works, but have no patience for finding patent articals. Is it on your site, or can you email it to me? Thanks, -Chris

10th September 2004, 09:42 PM	#4
johnsciolino diyAudio Member Join Date: Aug 2004 Location: florida	Patent your looking for Here you go on that patent http://patft.uspto.gov/netacgi/nph-P...&RS=4,752,745, Heres the tool for searching patents next time http://patft.uspto.gov/netahtml/search-bool.html

10th September 2004, 11:28 PM	#5
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	Thanks John, Turns out the site does not like Netscape. I had to use IE. I have some reading to do. -Chris

11th September 2004, 02:08 PM	#7
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	Thanks Steven, I'll try that one too. -Chris