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OPA1656: High-Performance CMOS Audio Op Amp
OPA1656: High-Performance CMOS Audio Op Amp
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Old 24th November 2020, 07:49 PM   #401
HpW is offline HpW
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Quote:
Originally Posted by syn08 View Post
OPA1656 is less noisy than the OPA827, 2.9nV/rtHz vs. 4nV/rtHz both flat.
See attached, Jan is using the opamp for his project MRK 3 input box (input attenuation & gain) prior an ADC for measurement purposes

Currently it is not clear, how the measurement (customer) setup was really done... balanced input & output of his upcoming gear

While did many noise simulation with LTSpice for a SVF notch (state variable filter) and the winner was always the OPA827 even in LTSpice FFT graphs.

Hp
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File Type: png Noise OPA827 vs OPA1656.png (19.5 KB, 528 views)
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Old 24th November 2020, 10:49 PM   #402
syn08 is offline syn08  Canada
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What should I look at? OPA1656 is clearly lower noise.

If you believe some simulation results over the datasheets that's your choice (and problem, I would say).

Last edited by syn08; 24th November 2020 at 11:12 PM. Reason: Typo fixed.
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Old 24th November 2020, 11:02 PM   #403
MarcelvdG is offline MarcelvdG  Netherlands
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1652?
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Old 24th November 2020, 11:44 PM   #404
chris719 is offline chris719  United States
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OPA1656: High-Performance CMOS Audio Op Amp
Quote:
Originally Posted by syn08 View Post
What should I look at? OPA1656 is clearly lower noise.

If you believe some simulation results over the datasheets that's your choice (and problem, I would say).
It is, wideband, for sure. Maybe he's talking about 1/f or strictly in a 20 kHz bandwidth where it may be close due to the higher noise corner.
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Old 24th November 2020, 11:58 PM   #405
syn08 is offline syn08  Canada
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Which is why I started the OP with:

Quote:
Originally Posted by syn08 View Post
Not sure if we have the same understanding of "noise figure"
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Old 6th December 2020, 10:09 PM   #406
chris719 is offline chris719  United States
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OPA1656: High-Performance CMOS Audio Op Amp
Apologies if this has been addressed by John in the thread already, but does anyone know if there are plans for a single version of this or OPA2156?
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Old 6th December 2020, 10:24 PM   #407
johnc124 is offline johnc124  United States
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Yes, there are definitely plans, the team is just spread really thin at the moment. But stay tuned, the single and quad channel options are on the way.
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OPA1637: New Fully-Differential Amplifier for Audio
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Old 19th December 2020, 12:46 PM   #408
Sam1964 is offline Sam1964
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Originally Posted by johnc124 View Post
The input stage on the OPA2156 is rail-to-rail, and uses slew boosting to improve the settling time (notice the higher slew rate). Slew boosting is something I don't think most customers are aware of, and we never really do it in audio power op amps.
PCM1704 datasheet
Quote:
Figure 5 shows single channel circuit connections for a typical PCM1704 application. It shows the PCM1704 interface to the digital filter, the I/V converter, and the DAC post filter. Selection of an appropriate op amp for the I/V converter is critical for obtaining optimum dynamic performance from the PCM1704. The OPA627 is recommended for this application. Op amps with similar characteristics and faster settling times may also be used.
ts Settling time

OPA627 0.01% 550 ns

OPA1656 0.01%, 800 ns
OPA2156 0.01%, 600 ns

Why it happens? Or is i / u not an audio?

Last edited by Sam1964; 19th December 2020 at 01:15 PM.
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Old 31st December 2020, 10:08 AM   #409
HpW is offline HpW
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Quote:
Originally Posted by syn08 View Post
What should I look at? OPA1656 is clearly lower noise.

If you believe some simulation results over the datasheets that's your choice (and problem, I would say).
After time, here to drawing's to compare:

. OPA1556 for audio

. OPA827 for instruments


while Jan's auto ranger is for measurement and sholul be ways better than the DUT.

IMHO, or 2 cents
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Old 11th January 2021, 03:35 PM   #410
Gonethesame is offline Gonethesame  France
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Hi, Would like to thanx Johnc124 for all the good advices , and all members to this thread.

just replaced my already very good opa2134 on my dac analog pre-output with the opa1656, and not only it keep warmness of the opa2134 but feeds more details to my Naim amp hifi system , which is amazing !

so one more time thx

G.
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