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Old 8th November 2004, 07:20 AM   #1
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Default Opamp for sell opa627ap/627bp/637bp/637au

I have many leftover opamps for sale:

OPA627ap X 8
OPA627bp X 5
OPA627au X 5
OPA637bp X 8
OPA637au X 5
OPA2227au X 5

I am taking offers. Send me a msg if interested.
Thank You
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Old 8th November 2004, 10:35 AM   #2
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Old 10th November 2004, 01:06 AM   #3
tg3 is offline tg3  United States
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Any comments on how these sound would be appreciated.

I'm looking for opamps for an active XO.
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Old 10th November 2004, 06:32 AM   #4
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the opa627 and opa637 sound fairly similar, both are great for making headphone amplifiers or such other devices.

4 X opa637bp is pending for sale by Hugh M.
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Old 10th November 2004, 05:53 PM   #5
Nisbeth is offline Nisbeth  Denmark
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Remember that the 637 is only stable at gains of 5 and over.
EDIT: So if you're in doubt, use the 627.


/U.
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Old 14th November 2004, 04:41 PM   #6
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I wonder if it is a coincidence that TI has samples available in quantities of 5?
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Old 14th November 2004, 04:53 PM   #7
roibm is offline roibm  Romania
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Quote:
Originally posted by KevinLee
I wonder if it is a coincidence that TI has samples available in quantities of 5?
LOL

Some 2-3 weeks ago I had a long discussion with TI(like 30 minutes). Lucky me I had a lot of notes next to me so the sales guy was very happy with all the feedback. They should start lifting up my samples limit from 5 to 10
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Old 16th November 2004, 06:11 PM   #8
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I tried both the ap as the bp versions of the BB OPA627. Though the A version is said to be better i heard no noticable difference.

To my opinion the 627 and the 637 sound very well, they are not as harsh as other opamps.
In a preamplifier i built i first used the Burr Brown OP27, later i stepped up to the OPA627, a major improvement.

Both the OPA627 as the OPA637 i tried in an opamp entrance based 50 watt class A Mosfet power amplifier with a balanced input, the opamps forced in class A too.
With the amplifier in class AB the OPA637 version sounded horrible, very nervous, fully in class A it sounds rather good.

I rebuilt 2 4-channel class A car amplifiers, replaced the dual opamp KIA4558s by OPA627 and the output devices by Sanken 2sa1216 and 2sc2922. The results sound pretty good.
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Old 16th November 2004, 06:22 PM   #9
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The BP version is the selected one that's better than the AP version.

Probably known but still: OPA637 can only be used at amplification of 5x or greater.

Decouple OPA627/637/AP/BP with 10 uF to 47 uF low ESR electrolytics like BG/Pana FC from both supplies to ground and use a 10 ( to 220 nF according to friend CarlosFM ) nF MKT cap with 5 mm pitch like Wima MKS 02 soldered directly on the pins. All three caps soldered as close to the pins as possible of course.

Don't believe it, please try it.

EDIT: sorry, I did not see the post of Nisbeth....
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Old 16th November 2004, 10:15 PM   #10
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I'm sorry, typo, you are right, the BP is better than the AP.

Offset voltage is about a third of the AP's, and OLVG and CMRR is a few db higher for the BP versions.
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