Best OP Amplifier in the World!! Look Amp Circuit

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NagysAudio

NagysAudio

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Joined 2006
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#1
Hi,

This is the absolute best OP amplifier circuit that I have ever heard! It can be used in amplifiers or preamps alike.

In amplifiers, this dual jfet input stage would be followed by a bipolar voltage stage and a mosfet output. (2sk134 and 2sj49)

The amplifier could have an extremely high frequency bandwidth and high slew rate, i.e. DC-500kHz at +/- 1dB.

I've been an audio engineer for over 11 years now and can tell you guys that nothing compares!

http://i189.photobucket.com/albums/z105/invictus005/OPAmp.jpg

Norbert
 
#2
Hello Nagys,

Thanks for sharing your interesting idea.

For info, some people have found advantage in the following:

1. Add a capacitor from the junction of the cascode resistors (51k, 33k) to ground, to reduce power supply influence on the bias voltage.

2. Replace the 75r resistors with a potentiometer (with the wiper connected to the "tail" of the differential), so that the off-set of the final circuit can be tweaked towards zero.

3. Use a LED to bias the "tail" constant current source instead of the zener diode, to increase CCS temperature stability.


Good luck.
 
#7
#10
2. Replace the 75r resistors with a potentiometer (with the wiper connected to the "tail" of the differential), so that the off-set of the final circuit can be tweaked towards zero.
Click to expand...
Hi,
do not deliberately unbalance the inherently balanced input stage.

Apply a correction elsewhere to zero out any DC output offset.

A discrete cascode Jfet input stage sounds quite normal, although the BJT version is a bit more common.
This type of circuit powers most competent power amp front ends.
Some builders even use part of a Jfet opamp input stage feeding the power amp to gain the advantage of the matched pairs (and laser trimmed) inside the IC.
 
#11
NagysAudio said:
Hmmm I agree it's a fairly standard circuit. But do you know of any amplifiers or preamps that use something similar? I would love to audition them!

Norbert
Click to expand...



Norbert, have a scout around the net, and use the search facilities on this forum, and you will find plenty of references.
 
#13
Hi Norbert,
Hmmm I agree it's a fairly standard circuit. But do you know of any amplifiers or preamps that use something similar? I would love to audition them!
Click to expand...
Looks very similar to one of the potted front end modules in a Luxman. Many amps use a FET diff pair cascoded with a pair of BJTs. A current mirror above completes the picture.


-Chris
 
#19
This original design is derived from the work of Dick Burwin, formally working at Analog Devices, later with Mark Levinson, in their hybrid group, in 1966. You can find this reference on Walt Jung's website in the historical section, somewhere.
I made a fet input and fet output version of this design in 1973 as the phono preamp stage of the Levinson JC-2. It is a GOOD, standard approach. Welcome to the real word of amplifier design, everyone.
 
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#20
NagysAudio said:
Hi,

This is the absolute best OP amplifier circuit that I have ever heard! It can be used in amplifiers or preamps alike.

In amplifiers, this dual jfet input stage would be followed by a bipolar voltage stage and a mosfet output. (2sk134 and 2sj49)

The amplifier could have an extremely high frequency bandwidth and high slew rate, i.e. DC-500kHz at +/- 1dB.

I've been an audio engineer for over 11 years now and can tell you guys that nothing compares!

http://i189.photobucket.com/albums/z105/invictus005/OPAmp.jpg

Norbert
Click to expand...
You like only 'the best ever...' 🙂
Regards
 
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