ADA 4627 (ADA4627-1) outperform Burr Brown's OPA 627 (OPA627) - Page 3 - diyAudio
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Old 31st January 2012, 08:08 AM   #21
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Quote:
Originally Posted by fjc View Post
Test on sonic difference,
Anyway, I made listening test on ADA4627 Brz and 4637 Arz.
Sonically they are not much difference. Check the spec, 4627 has a 18 V/us slew rate, normally this should be enough for an audio purpose OP. 4637 has much faster slew of 100s. My feeling is the resolution of 4637 is slightly better,but the major difference is the sense of the instrument locations. It is more alive and sharper image for 4637. In other words, 4627 is more flat. I vote for the 4637, even it is a cheaper A version used.
These differences correspond to those, which I have in mind from the 80s - by a listening test between Raytheon's OP27 and OP37 in the TO outline - go to
OP-37* datasheet and application note, data sheet, circuit, pdf, cross reference, pinout | Datasheet Archive
and
OP-27 OP-27 Noise Operational Amplifier Very noise Spec | Datasheet Archive
for download the associated datasheet.


BTW I am still looking for the internal schematic of ADA4627/4637.
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Old 1st October 2012, 08:20 PM   #22
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Default ADA4627 designed as a 100% drop-in replacement of OPA627 ?

I just recently ran over the ADA4627/37 again for a different purpose than Audio (optoelectronics frontend), but when I saw the large signal step response of the ADA4627 I had a deja vu.

I know that only a very few OPAs do this very strong "snap" during negative slew. One of the very few types with this behavior is the .... OPA627 ! See apended picture. With the very similar performance characteristics on top of that, I would think, that the ADA4627 was planned as a 100% drop-in replacement, otherwise ADIs engineers certainly had eliminated this old fashioned misbehaviour.

From the engineering point of view, really good drop-in replacements use the same circuit as the "original", so I would expect that the ADA4627 is based on the same basic circuit as the OPA627, with some minor improvements, which don't influence drop in compatibility, like better clipping response etc.

Hopefully they didn't introduce additional substrate diodes into the inputs. In this case the OPA4627 could be as "perfect" in common mode distortion with high source impedances as the "original" (See Samuel Groner's OPA paper on this), with some very nice niche applications like buffer for high impedance volume pots etc.

This beast is certainly worthwhile a little bit of measurements to find out, what it's real strengths are (Not alone listening, because ears are often an inappropriate means to differentiate the subtle differences of modern OPAs).
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File Type: jpg OPA627 vs ADA4627.jpg (70.2 KB, 545 views)
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Old 3rd December 2012, 12:34 PM   #23
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I've used ADA-4627 for 1 year, I used it to replace old type Motorolla opamp in MSB link III. Before that, for short time I use LM4562 in that MSB (standard parts).

From Motorolla to LM4652, I hear increase of detail, sounds more natural and bit thinner bass but more punchy and faster than motorolla.
From LM4652 to ADA-4627, I hear more warm vocal, detailed sound especially in midbass and vocal (I don't know how to describe it, more thicker??). But when I compared it to my Musical Fidelity A324 - heavily modified components with LM4652HA (tin casing), the sounds of MSB almost close enough with MF but modified MF sounds more refine, smoother (less grain), and wider soundstage but MSB bit more punchy.

I haven't have time to use ADA4627 in MF, I'm too tired enough when I upgrade in trial error MF almost 1.5 years (sigh...) but I will someday
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Old 18th September 2013, 05:04 PM   #24
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What I must cosider by the use of such OP-Amps in parametric equalizers like this one from UREI - go to
Urei 545 Parametric Equalizer Schematic
The Musician's Room: What's New?
Thank you for advices.
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Old 19th September 2013, 04:28 AM   #25
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Hi Guys
Just for fun. I'm putting up a link of my latest studio recording effort.
It's not a perfect mix but the drums, vox, lead guitar, djembe and ac guitar all used Trident Fleximix mic pre's loaded with 4627-1 BRZ in the first stage and LM6171 in the second stage.
Unfortunately, I had the 70Hz filters on the two drum mics.
Bass going in direct through a 12AX7 smooth plate loaded Demeter VTBP-1.
I am going to put them in my mastering stereo compressor/limiter and see if that doesn't thicken things up a bit.
Hope you like.
https://app.box.com/s/qqgmzqpeu8ck39lb9eop
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Old 1st December 2013, 11:40 AM   #26
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In comparing the spec sheets of OPA627B and ADA4627B-1, the current noise specs are identical (1.6fA @100 Hz), and the voltage noise favors the 627 only slightly (4.5nv/6.1nv). The 4627 is faster the the 627 (82v/uSec vs. 55), but in inverting mode only. The common-mode rejection is identical at -116 db, and the THD specs are also quite similar, with the 627 having a -3db advantage. But the BIGGEST difference is the $$$$---checking Mouser prices, the OPA627s are $34.65 EACH; the 4627s are $10.76 apiece. As the specifications are quite close to one another, methinks the better than 3x price difference makes the 4627 the clear winner.
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Old 8th February 2014, 01:18 PM   #27
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Default 4627 vs 4562

Now, I understand the advantage of using a JFET opamp (ADA4627) as opposed to a bi-polar(LM4562) when the source is high impedance, such as a guitar pickup----lower current noise. But, what about AFTER the original input gain stage? Does the 4562's superior THD trump the 4627 in all remaining circuit applications? Such as equalization, buffering, gain control, et cetera?
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