OP-AMP based balanced horisontal amp....

Circlomanen · 17th July 2005, 11:06 AM

I saw some other op-amp biased fetamp so I thought I would post this one. No bias circuitry is drawn in the picture. Just the basic amp. As it is now it runs in class C. Not any sweetsounding but its just an idea.
Any thoughts or comments????

djk · 17th July 2005, 04:40 PM

Bias will be really tough unless you run class A or L-MOS.

B+ maximum for outputs is about 44V (about 60W/8R) for the OPA2604 running off ±24V.

Higher voltages may be used but it can get very complicated.

aparatusonitus · 17th July 2005, 06:52 PM

Looks like Sumo Nine(+), except mosfet output, deseign by James Buongiorno.

http://photobucket.com/albums/v58/ap...rent=Sumo9.jpg

djk · 17th July 2005, 09:45 PM

Very much so except:

The variable bias scheme should not be tried with FETs.

The high voltage LF 353s were obtained by selection for ±20V. An OPA2604 sounds better and will work at ±24V without selection.

Bongiorno says the AD823 selected for ±20V use is even better.

Workhorse · 18th July 2005, 12:58 AM

Check this out

Its an opamp driven N- channel vertical mosfet amplifier

http://www.qscaudio.com/support/library/schems/pl90.pdf

andreie · 18th July 2005, 08:59 AM

Why should bias be tough?

Perhaps the following completes the picture:

This is a modifcation from a design in "Radio" August, 1984 issue, pages 35-37.

Don't ask about the sound, because I never got around building the first time I saw it and later I found Renardson's 7-transistor amplifier, which is technologically superior to DIY.

17th July 2005, 11:06 AM	#1
Circlomanen diyAudio Member Join Date: Sep 2004 Location: Göteborg	OP-AMP based balanced horisontal amp.... I saw some other op-amp biased fetamp so I thought I would post this one. No bias circuitry is drawn in the picture. Just the basic amp. As it is now it runs in class C. Not any sweetsounding but its just an idea. Any thoughts or comments???? __________________ We live in a horizontal world, why use vertical topologies???

18th July 2005, 12:58 AM	#5
Workhorse diyAudio Member Join Date: Dec 2004	Check this out Its an opamp driven N- channel vertical mosfet amplifier http://www.qscaudio.com/support/library/schems/pl90.pdf __________________ It's a fruitless endeavor to try and educate a fool that rejoices in ignorance

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17th July 2005, 04:40 PM	#2
djk diyAudio Member Join Date: Feb 2001 Location: USA	Bias will be really tough unless you run class A or L-MOS. B+ maximum for outputs is about 44V (about 60W/8R) for the OPA2604 running off ±24V. Higher voltages may be used but it can get very complicated.

17th July 2005, 06:52 PM	#3
aparatusonitus diyAudio Member Join Date: Jan 2004 Location: Split, Croatia	Looks like Sumo Nine(+), except mosfet output, deseign by James Buongiorno. http://photobucket.com/albums/v58/ap...rent=Sumo9.jpg

17th July 2005, 09:45 PM	#4
djk diyAudio Member Join Date: Feb 2001 Location: USA	Very much so except: The variable bias scheme should not be tried with FETs. The high voltage LF 353s were obtained by selection for ±20V. An OPA2604 sounds better and will work at ±24V without selection. Bongiorno says the AD823 selected for ±20V use is even better.

18th July 2005, 08:59 AM	#6
andreie diyAudio Member Join Date: May 2005 Location: Tallinn	Why should bias be tough? Perhaps the following completes the picture: This is a modifcation from a design in "Radio" August, 1984 issue, pages 35-37. Don't ask about the sound, because I never got around building the first time I saw it and later I found Renardson's 7-transistor amplifier, which is technologically superior to DIY.

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