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Old 22nd August 2003, 11:55 AM   #16
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I believe that the OP27 and OP37 that people are reffering to are from Analog devices.
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Old 22nd August 2003, 12:14 PM   #17
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Quote:
Originally posted by Bricolo
I can't find the OP37 on TI's website, it it discontinued?

But I can find the OP27, OPA27 and OPA37
Search word OP37 and I get this
http://focus.ti.com/general/docs/sit...tatusCode=null
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Old 22nd August 2003, 12:19 PM   #18
Bricolo is offline Bricolo  France
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discontinued...
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Old 22nd August 2003, 12:21 PM   #19
Bricolo is offline Bricolo  France
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don't TI build high quality dual opamps?
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Old 22nd August 2003, 03:49 PM   #20
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I believe that OP37 is an Analog Devices part number and OPA is the Burr-Brown (TI) part number.

I've been looking at the OPAx227. Anyone have experience with it.

:)ensen.
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Old 22nd August 2003, 04:41 PM   #21
Bricolo is offline Bricolo  France
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Quote:
Originally posted by purplepeople
I believe that OP37 is an Analog Devices part number and OPA is the Burr-Brown (TI) part number.

I've been looking at the OPAx227. Anyone have experience with it.

ensen.

You're right, OP37 is AD
but OP27 is TI AND AD
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Old 22nd August 2003, 04:49 PM   #22
Bricolo is offline Bricolo  France
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BTW, how do you all select wich opamp to use?

Look at AD's website, this is such a mess.
What do you choose between high speed, low distortion, low noise, precision or everythingyouwant opamps?
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Old 22nd August 2003, 08:01 PM   #23
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Default OPAx227

Hi guys!

Have used the OPAx227 (OPA2227-dual, OPA4227-quad) for signal conditioning with great success.

JojoD
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Old 22nd August 2003, 10:39 PM   #24
PRR is offline PRR  United States
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> Hey when do I get off newbie moderation - it's rather annoying!

Took me 10 posts, even being very careful not to offend ANYBODY.

Apparently this forum has a sad history of unmoderated flame-wars. The current moderators worked hard to clean it up, for which we are very grateful.

However, I wonder about this extended newbie-choke. In My Experience (years as moderator at another forum) the newbies do not cause as much trouble as the Old Members, who have been around long enough to think "their" forum is a personal pooping-place.

Maybe your first post should be unmoderated, but your 50th and 100th posts should force a moderator re-evaluation of your behavior? (Boy, I would hate that even worse than the 10-newbie moderation...)
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Old 23rd August 2003, 01:58 AM   #25
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Default Re: OPAx227

Quote:
Originally posted by Bricolo
BTW, how do you all select wich opamp to use?

Look at AD's website, this is such a mess.
What do you choose between high speed, low distortion, low noise, precision or everythingyouwant opamps?
Since I haven't played with opamps since school, when it was only with the venerable 741, I am forced to look at the well-known devices first.

Since Burr-Brown (and now TI) is the maker of extremely well-regarded linear ICs, I've decided to examine their line of opamps - OPA27/37, OPAx134, OPA604, and OPAx227/228. The 227/228 intrigues me because it is comparable in price to the others (Digikey) and still labelled as suitable for professional audio.

As an industrial designer, AD's website philosophy leads me to believe that their products may suffer the same poor design.


Quote:
Originally posted by JojoD818
Hi guys!

Have used the OPAx227 (OPA2227-dual, OPA4227-quad) for signal conditioning with great success.

What do you mean signal conditioning? What kind of conditioning? Audio signals?

:)ensen.
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Old 23rd August 2003, 05:15 AM   #26
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Default Signal Conditioning

Hi purplepeople,

When I said signal conditioning, I meant mic preamps, signal buffers, tone controls, equalization, filters, etc.

Cheers,
JojoD
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Old 23rd August 2003, 02:24 PM   #27
kyrgeo is offline kyrgeo  Greece
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Thumbs up check these out

Some interesting chips spec-wise:

opa655 vfb, fet input, look at open loop gain vs frequency
ad9631 vfb, quad core input stage, look at open loop gain vs frequency

ad8021 vfb, drive external buffer by comp pin, bypassing internal output stage
ad8008 and ths3001 favourite cfb opamps

Especially the first two are very interesting. With only 60db open loop gain (it _is_ low for opamps) flat up to 100kHz, and _really_ low distortion, they seem to be very linear, even before feedback is applied. Most other chips I know of rely on >90db of feedback to bring distortion down at low frequencies.
Another thing that makes them stand out is the high quiescent current 15-20mA, wich is a big plus in my opinion.
warning: very high speed parts

Note that I have not tested them yet. They are difficult to find around here.
Has anybody used them? Any comments?
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Old 24th August 2003, 07:20 PM   #28
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I've only started looking at the data sheets and I think the pattern I'm seeing is that the audio opamps perform very well at f<200kHz while the high bw opamps only start to work well f >= MHz and are quite bad performers f<.5MHz.

It's also interesting to note that the performance drops off dramatically for audio opamps f>200kHz

It could be that regardless of the general specs, the opamps recommended for audio will sound better than the others.

:)ensen.
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Old 24th August 2003, 08:40 PM   #29
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Default Re: check these out

[QUOTE]Originally posted by kyrgeo
[B]Some interesting chips spec-wise:

opa655 vfb, fet input, look at open loop gain vs frequency
ad9631 vfb, quad core input stage, look at open loop gain vs frequency

------------------------------------------------------
Trouble is: they atre only good for +-5V operation; no good as replacements. Naturally current is higher.
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Old 25th August 2003, 06:07 AM   #30
cdl is offline cdl  Denmark
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Hello everyone,

I replaced OP37 with OPA627 this weekend [see schematic in one of my previous posts], and the difference is striking. OP37 wasn't bad, but after the opamp replacement, sound is much more natural and also seems more detailed.

Vocals sound much better, the S-sounds are more controlled.

But I will continue trying out at least AD825 and AD8610. Will keep posting.

What is interesting for me is definately the sound (musicality) and not measured performance - for me, parameters like slew rate, frequency response etc. may be hints as to how a component may perform - not the holy grail.

When considering components with >MHz performance, it might be relevant to keep in mind that (at least playing CD) everything above 20kHz is filtered away anyhow, and what signal might remain in the MHz region is going to be ugly digital noise that noone wants anyway!

/cdl
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