OPA627 as input stage? Output can be BJTs.. - diyAudio
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Old 13th September 2012, 08:38 PM   #1
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Default OPA627 as input stage? Output can be BJTs..

I have seen somebody talking about this schematic where the input is handled by OPA627 and output is some pushpull stage... is it really possible to use opa627.. some say this chip is better than many discrete designs which I dont believe tough. But Is it really possible to use this as input stage?
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Old 13th September 2012, 09:50 PM   #2
jcx is online now jcx  United States
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for what?

mm phono pre amp

line driver/headphone amp

audio power amp

I'd guess you could find examples of each - simple enough to put your choice op amp in front of a chip amp in a multi-loop for power
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Old 13th September 2012, 11:19 PM   #3
tvrgeek is offline tvrgeek  United States
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Yes possible. Yes it is very clean. IPS is a current amplifier and must operate at voltages compatible with the VAS. That makes a chip op-amp not always a great IPS.
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Old 14th September 2012, 02:38 AM   #4
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how is it possible is there any schematic?
btw how is it possible I believe AD815 can do the job. Are you talking about the Voltage source or voltage output / current output?

as a current amplifier how many milli amps do we require? to drive a 2k1943
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Old 14th September 2012, 04:01 AM   #5
jcx is online now jcx  United States
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diff pair, even VAS usually don't drive single push-pull transistor pair output stages at high power, or current either so why would you expect "op amp as front end" to have to

dual, triple followers, or CFA are pretty standard in BJT power amp output stages, most competent designers recognize even MOSFET output require drivers to handle output Q gate dynamic currents

Last edited by jcx; 14th September 2012 at 04:19 AM.
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Old 14th September 2012, 04:40 AM   #6
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OPA627 & LYNX
http://audio-circuit.dk/images/LYNX-v3-0-QAG.pdf
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Old 14th September 2012, 07:25 AM   #7
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did anybody auditioned this?
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Old 14th September 2012, 10:21 AM   #8
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since its pretty good opamp that should be sounding good. Any reasons why cant one use them?
IMD would be high but how about the sound quality altogether?
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Old 14th September 2012, 10:24 AM   #9
Boscoe is offline Boscoe  United Kingdom
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An op amp has very low distortion easy and air current drive why not use it as an IPS?

Because its easy and people can't understand why something easier could be better, peoples pre conceptions make things sound different not the equipment. Most of the time.
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I thought about it once, but then thought again.
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Old 14th September 2012, 02:13 PM   #10
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i think the above schematic doesnt even need a preamp section...
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