Which Op-Amp? (Afraid to ask really...) - diyAudio
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Old 5th February 2009, 01:15 AM   #1
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Default Which Op-Amp? (Afraid to ask really...)

I am a long time tube guy that has some sand experience. I recently built a couple op amp RIAA preamps with the BA4560 and the TLO82CP. The TLO82 definitely has an edge over the 4560 -- there is a lack of harshness on the high end that is clearly apparent. That has made me want to explore more sand amps while I build some tube RIAA preamps. I've looked on the site for well over a week and these are the op amps i've found highly praised on DIYAUDIO. I am looking for input on these (they have current digikey cost). I want to do some swapping, but I don't want them all... I only need a couple really... if you could get 4 or 5 of these, which would you get? Or would you get something else. PLEASE NOTE, I am using 8 pin DIP sockets, so no SOIC, etc... DIP available only please!! Thanks!


LME49720 -- $4.53

LM4562 -- $4.53

AD826 -- $5.60

AD823 -- $5.90

AD797 -- $8.76

AD711 -- $2.66

OPA228 -- $5.02

OPA227 -- $3.53

OPA37 -- $2.57

TLE2071 -- $1.75
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Old 5th February 2009, 04:15 AM   #2
tedr is offline tedr  United States
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Which are designed for audio? Check the data sheets, if it was designed for audio it will say so, no point in making things more difficult. I would explore the ones specifically designed for audio first, like the dinosaur, but still usable TL072 and 5532, and some newer parts from national and Texas Instruments designed for superior audio quality. Pick something intended for audio use, slew rate matters, noise matters, distortion matters, whereas input current, DC offsets and drift don't matter a damn!

Ted
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Old 5th February 2009, 10:06 AM   #3
Calvin is offline Calvin  Germany
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Hi,

I disagree in part.
Distortion values (2nd and 3rd) and slewrate values as printed in the datasheets are very unimportant for audio usage like high level analog amplification, filtering and phono (except for ADCs and DACs).
Noise figures do matter as do Offset and input currents, especially for Phono where the highest gains will occur. High input bias currents of bipolar lownoise OPamps can create output offset voltages of several hundreds of mV! So if You use such OPamps You will have to keep the Offset-issue in mind.
Depending on the toplogy of the circuit You choose the OPs.
My favourites are 2-stage circuits with splitted passive/active RIAA-equalization. A first linear amplification stage with dc-servo or dc-blocking cap (20Hz after RIAA/IEC), followed by a passive 2120Hz filter and a second gain stage with active 50Hz-500Hz-equalization. This gives the best SNR-figures, the most precise equalization, very high flexibility and low distortion (with senible effort regarding cost and complexity of the circuit).
When You use the stage for MMs only You can choose bipolar as well as JFET-OPs for the first stage, when using MCs only a few bipolar OPs meet the noise requirements. For the second stage I´d always choose a JFET OP (high source impedances from the filterstage before).
Something like this one: http://www.matuschek.net/platina/

jauu
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Old 5th February 2009, 11:29 AM   #4
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Quote:
Originally posted by tedr
whereas input current, DC offsets and drift don't matter a damn!

Ted

Maybe not to you. Why would input current not matter to someone with a low output MC? I have a DC coupled opamp phono stage in which low and stable dc offset is crucial. Otoh, can't care less if a part was meant for audio or not.
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Old 5th February 2009, 11:40 AM   #5
Serge66 is offline Serge66  Switzerland
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Greetings,

This site may give you some good insights:

http://www.dself.dsl.pipex.com/ampins/webbop/opamp.htm

Serge
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Old 5th February 2009, 11:46 AM   #6
Mooly is offline Mooly  United Kingdom
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OPA604 ( single )and OPA2604 (dual ) can sound very tube like with sympathetic design. Even harmonics predominate... still my first choice. Add a 0.1mfd on the supply pins directly if poss... very carefully solder to the top of the pins. You won't be dissappointed.
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Old 5th February 2009, 11:21 PM   #7
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Serge66, thanks for the link will read it in its entirety later this evening.

I should add, I do not need help with schematics, etc at this point. Merely labeling a part AUDIO doesn't sell it to me either.

I have a really nice table, stereo and speakers, so it's easy to tell things apart. So to kind of restate what I was wanting -- I am looking for SUBJECTIVE input on these opamps. Which have you used and LOVED because it sounds great. I am not wanting to debate specs or topologies in the least.

Again, looking for the "best sound" -- subjective opinions are most welcome.
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Old 6th February 2009, 12:04 AM   #8
kaos is offline kaos  United States
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Sorry for the bad news, but no one op amp has the “best sound”. They all have different subjective strengths and weaknesses. What’s chosen depends on the application, surrounding circuit, and personal taste. Unfortunately there’s no substitute for personal experience regarding which one that’s preferred. If you really want to find what you like, you’ll have to make a longer list than just a couple based on other’s recommendations. I’ve tried over 25 different types myself, and still remain to be pleased when comparing them to a good discrete Lin design.
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Old 6th February 2009, 01:51 AM   #9
tedr is offline tedr  United States
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Personally I find I care about the sound of the music that moves me. I want the opposite from my equipment, that has to be as neutral as possible. Trying to select opamps for subjective qualities is a fools errand because it all depends how you use them. Chose them because they do the job of creating a neutral channel, that is something that can be done.

Ted
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Old 6th February 2009, 03:41 AM   #10
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LME49720 -- $4.53 = "Dual High Performance, High Fidelity Audio" ( http://www.national.com/pf/LM/LME49720.html ) ... low THD+N and a good slew rate.

LM4562 -- $4.53 = Ferd's likes 'em enough to be a part of a "mod" upgrade to NAD CD player ( http://www.ferdsaudio.com/CDmods/C542.htm )

AD826 -- $5.60 = Op-amp input as part of A to D converter ... not for the playful or faint of heart. ( http://focus.ti.com/docs/prod/folders/print/ads826.html )

AD823 -- $5.90 = "" ""

AD797 -- $8.76 = Single channel for Instrumentation use ... very good specs but at least 2 req. for audio ( http://www.analog.com/en/other/milit...s/product.html )

AD711 -- $2.66 = single channel instrumentation amp, again, best to look at the AD712 ( http://www.analog.com/en/prod/0,2877,AD712,00.html ). IMOP Analog makes some of the best, but steal your circuit suggestions from TI or National = they cheat and the overall results may be equal or better.

OPA228 -- $5.02 = TI / Burr-Brown = http://focus.ti.com/docs/prod/folders/print/opa228.html ... always a good choice, can't go wrong ( http://www.ti.com/lit/gpn/opa228 )

OPA227 -- $3.53 = """ """

OPA37 -- $2.57 = "Ultra-Low Noise, Precision ..." = http://www.ti.com/lit/gpn/opa37.pdf or search

TLE2071 -- $1.75 = "Excalibur Low-Noise High-Speed JFET-Input ..." JFET is GOOD, but a bugger to get perfect

Single channels for great separation, dual channels for easy circuit design ...
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