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Old 17th December 2011, 11:37 AM   #1
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Question Simple question about OP27

Hi everybody,
first of all, sorry for my bad english, i hope i can explain all i want and you can understand me.

Please, i've searched in the internet but i can't find the right answer.

I want to build a very simple Preamp with op-amps and make some tests with op-amps i have. Because it'is for me a little difficult to build a PCB with a single o-amp, i decided to use only dual op-amps.

So, what is the right equivalent of OP27 but DUAL? (if exist...)

Many thanks to everybody can help me...
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Old 17th December 2011, 11:51 AM   #2
AndrewT is offline AndrewT  Scotland
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search
dual opamps
__________________
regards Andrew T.
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Old 17th December 2011, 12:31 PM   #3
tvrgeek is offline tvrgeek  United States
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If the PCB is causing you worry, might pick up a "kit" preamp board off e-bay, and use the board. Play with decent op-amps, caps etc. Or for far better quality, see what Ron Elliot has to offer. Even generic IC vector boards are pretty easy.

I did most of my playing around picking chips with a clone of a Grado headphone amp for a dual DIP and for smt, a couple of e-bay generic headphone amps.

Build singles is just as easy as a dual. Just build two!
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Old 17th December 2011, 04:46 PM   #4
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Quote:
Originally Posted by AndrewT View Post
search
dual opamps
i've searched dual opamps!!!!
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Old 17th December 2011, 04:48 PM   #5
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Quote:
Originally Posted by tvrgeek View Post
If the PCB is causing you worry, might pick up a "kit" preamp board off e-bay, and use the board. Play with decent op-amps, caps etc. Or for far better quality, see what Ron Elliot has to offer. Even generic IC vector boards are pretty easy.

I did most of my playing around picking chips with a clone of a Grado headphone amp for a dual DIP and for smt, a couple of e-bay generic headphone amps.

Build singles is just as easy as a dual. Just build two!
No, i don't want a kit.
Thanks
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Old 17th December 2011, 05:24 PM   #6
jcx is offline jcx  United States
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Precision Amplifier - Low Offset Voltage - OPA227 - TI.com

TI now owns National so the op amp seach tool shows "audio" LME series parts too - much better numbers than the op27


unless you really need the lowest Voltage noise performance for phonograph Moving Coil preamp then FET input op amps can have advantages - even with Moving Magnet cartridge

Last edited by jcx; 17th December 2011 at 05:30 PM.
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Old 18th December 2011, 06:51 PM   #7
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I want to use OP27 because Elektor Magazine used many times and says it's one of the best sounding...
Now i want to try NE5534, LME49720, OPA2134, LM6172 and LT1364, i want to hear myself the differences, if exists some...
Thank you.
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Old 19th December 2011, 12:53 AM   #8
jcx is offline jcx  United States
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the original Analog Devices OP27 is pretty old now, was designed for "precision" - low Vos, very high gain, diff pair biased for optimum noise performance with < ~ 1 KOhm circuits with the best possible "DC" specs - excels at sub 10 Hz noise
slew rate is poor by today's standards, likely EMI rectification in the diff pair front end is not as good as can be had today

the TI/BB second source OPAx27 is basically similar

while I don't believe in most "just listen" reports of "sound" for correctly selected op amps I see no reason to go out of the way to use such an odd "vintage" part when all of its specs for audio applications can be bettered, with 20 yrs evolution in semi processing and circuit topology

AD did market the O27 as suitable for professional audio - doesn't mean you should believe it or anyone who may be echoing the datsheet blurb - you can certainly find comments that the OP27 in fact sucks for audio



many here seem to have missed the fact that A/DSL modem, medical imaging applications demand for low distortion, IMD, noise, drove a massive investment in isolated processes with well matched, fast transistors, and increased design sophisitcaion for low distortion at up to 1 MHz with broadband signals

the best of last decade's new monolithic op amps are a meaningful step above "classic" op amps for audio designed in the 1980-90's when properly applied for the circuit - no one part is "best" over all possible audio circuit applications: MC vs MM preamp, DAC I/V, active XO, ...

Last edited by jcx; 19th December 2011 at 01:19 AM.
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Old 20th December 2011, 08:49 AM   #9
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ok, i understand your explanation.
all the problem is because i have 4 op27 (buyed many many years ago) and it is for me difficult to make a pcb (more simple with a dual opamp).
so, if i can i will try, or i searche for other op. thanks!!
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