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Burr Brown Chips

Discussion in 'Effects [BG]' started by BawanaRik, Mar 25, 2013.


  1. BawanaRik

    BawanaRik Supporting Member

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    Location:
    New Jersey
    I have a Hematoma and am wondering if replacing the stock op amp with a Burr Brown OPA2132 would be a noticeable up grade or do I have too much time on my hands?

    Has anyone tried this? Do the "better" chips sound "better" or is it a waste of time and money?

    Comments?
     
  2. boomertech

    boomertech Gold Supporting Member

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    Designer/Owner of FEA Labs
    I think the general consensus is that most of the time changing out the opamp does not make a noticeable difference in the tone of a pedal. Visual Sound (I think) did a youtube video dispelling the opamp upgrade myth.

    But I have seen where changing the opamp can make the circuit unstable… oscillations, nasty phase reversal when hitting the rails and difficulties driving heavy or capacitive loads differently. I have also seen where two opamps have very similar spec's and one will work in a circuit just fine where the other one will not.

    Then there are the low budget, general purpose op’s that distort in a musically pleasant way that become the Holy Grail of tone for some people.:)


    -Frank
     
  3. SirMjac28

    SirMjac28 Patiently Waiting For The Next British Invasion Gold Supporting Member

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    And when Frank says something I believe it even if I don't understand the technical stuff the guy is a mad scientist. :)
     
  4. BawanaRik

    BawanaRik Supporting Member

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    I remember a LONG time time ago when I was a kid one of my professors telling the class about a circuit that required just the right brand as well as type of tube to work. Other brands wouldn't work.

    Try telling your boss or purchasing that story.

    I guess there's a little mojo in electronics after all.


     
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  6. Joe Louvar

    Joe Louvar

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    Santa Rosa, CA USA
    FWIW: Burr Brown OPAs are nice (clean), and many cheaper "preamps" have successfully been upgraded with them - scan the nerdy pro audio/recording forums. EDIT: But I'm not sure it's something you'd want to change in an effect.
     
  7. boomertech

    boomertech Gold Supporting Member

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    I absolutely love Burr-Brown opamps, they seem to be a great workhorse for more complex and demanding audio circuits.

    I remember reading about a builder of a very popular overdrive burning-in and hand selecting opamps for the ones he would use in his pedals.

    I suggest that if you want to swap opamps to install an IC socket to prevent PCB damage… it can be a lot of fun!:bassist:

    -Frank
     
  8. seanm

    seanm I'd kill for a Nobel Peace Prize!

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    Location:
    Ottawa, Canada
    I think the answer is "it might be better... or worse". There are times when the chip doesn't matter: even the cheapest opamps work well as buffers IMHO.

    There are times when the designer designed to a specific opamp to get the desired sound. For example, an overdrive or distortion might not want a truly clean opamp. There is one where this is true, but my poor memory cannot remember :( DOD 250 maybe?

    IMHO, where you want a really good opamp is in something you want very clean: a preamp or EQ or compressor. Anywhere where you have "noise" you are probably wasting your time
     
  9. Flux Jetson

    Flux Jetson

    Joined:
    May 3, 2012
    Location:
    Colorado River Basin, Arizona
    Some compressors benefit greatly with the use of the BB IC, and TS9 type distortions definitely sound different with the BB installed, they have less of a mid-hump than when using the JRC4558D IC.

    Whether or not the Burr Brown OPAx13x sounds any "better" depends on two things:

    1.) Which circuit we're talking about.

    2.) How you define "better" .. and when I say ~you~ I mean YOU. Everyone has their own ideas about what "better" is.

    Best suggestion:

    Install an 8-pin IC socket and get after it! Start trying different ones. Do a little begging from forum members, a little trading, a little buying, collect a few different brands. I'd tell you to ask various vendors for "samples" but the sample policies are actually for builders that will be buying hundreds/thousands of them if they work out. The sample policies of most vendors have been so severely abused by "beggars" and DIY people that just want free parts that many vendors no longer have sample policies any more. Regarding the IC sockets, I might suggest using the MACHINE TOOLED IC socket instead of the crappy Radio Shack looking one.

    The one on the left is not as good as the one on the right. The right one has better sockets that make better contact with the pins on the IC, and it also has actual sturdy ~pins~ that get soldered into the pads on the PCB. And if it matters to you, the right one has gold plated sockets that some folks say is more resistant to corrosion and oxidation which can futz with the way everything works if it gets bad enough.

    The left one has these crappy little thin strips of sunthin sunthin that get soldered to the PCB, and the socket contacts aren't as ~certain~ when the IC pins are installed in it.

    The advantages of the left one are that it's less expensive (by like $0.50) and it has an overall lower profile when the IC is pressed into it. So if you are saving actual pennies, and have a vertical space issue in the pedal, then the left one is the better choice.

    [​IMG]
     
  10. BawanaRik

    BawanaRik Supporting Member

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    Where are the better ones available?

    Thanks


     
  11. Flux Jetson

    Flux Jetson

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  12. Jordan S.

    Jordan S.

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    Blacksheep Effects Pedals
  13. johnk_10

    johnk_10 vintage bass nut Supporting Member

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    John K Custom Basses
    IME, in some pedals, changing chips makes a pretty big difference, while in others, not much at all. for example, for me, generally, the BB chips sound a little darker than a 'standard' TL072 and have less of a mid hump than a JRC4558D.
     
  14. Flux Jetson

    Flux Jetson

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    That's pretty much exactly what I said too. :)
     
  15. boomertech

    boomertech Gold Supporting Member

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    Here is the Visual Sound opamp myth buster video…



    These are the opamp’s that were A-B tested against the JRC4558 in a VS-808 pedal (tube screamer clone).
    1. JRC4558 vs TI RC4558 The same opamp by different manufacturers they have PNP front ends.
    2. TLC2272 CMOS front ends and r-r output.
    3. C4558 Magic Mojo… never heard of this opamp before. I probably wouldn’t even consider using one of these because it is named for hype.
    4. LM833 PNP front ends (nice GP audio amp)
    5. JRC072 FET front end same as the standard TL072
    6. MC14577 CMOS video amp (fast)

    I have tried several opamp swaps in my TS clone with the same results of this video.:bag:

    When manufacturers test their opamps for data sheet information they use a very, very, very simple non-demanding circuit. So if you were to swap the 2132 Burr-Brown with 0.00008% THD with a TI TL072 with 0.003% THD you wouldn’t hear a difference between them in those simple test circuits. Our hearing can not detect those miniscule differences in distortion. The slight differences in tone will be with how they behave with more complex circuits and operating points. Capacitive loading, heavy output loads, amplitude demands, unity gain stability… etc. all make a contribution on how the tone is changed between them. Then when the opamps are pushed beyond their operating point all sorts of odd things can happen… latch-up, phase reversal, output sag, oscillations, how it clips the rails… etc. Thus the circuit around the opamp has a much greater impact on the tone heard. A lot of mojo that people want is not with the opamp operating properly, but how it is being pushed into nonlinear distortions.

    I too have heard subtle differences in the mids with the 2132 Burr-Brown vs a TL072 in a clean amp circuit. The subtle difference that I observed between the two was easily erased with a very slight adjustment of the high freq EQ. Then in a different clean amp circuit I heard no difference at all. The B-B can drive 600 ohm loads whereas the 072 starts to really struggle with loads less than a few Kohms. I have seen where a 072 will throw out nasty phase reversal spikes when hitting the rail and the B-B will just clip normally at the rail. When the 072 threw out the phase reversal spikes it dumped all sorts of noise on the power rails. Then from the same lot of 072’s some would clip naturally without phase spikes. Thus, designing a circuit around an opamp operating outside of its recommended specs would give sketchy repeatability at best. You would have to hand select every opamp for the behavior that you were looking for.

    Swapping a FET front end amp like the B-B 2132 or 072 with a PNP front end amp like the 4558 will increase the input capacitance at the opamp. The increased capacitance will result a natural low pass filter rolling off the high freq’s in some circuits. IME with a little redesign of the surrounding circuit with the 4558 it can be made to sound very similar to the FET opamp circuits.

    Just to echo what has already been said… install a socket and have fun.:bassist: Try several manufactures of the same chip and try several chips from different lots. Also be aware that there are counterfeit’s out there on the internet… get your parts from a reputable source.

    -Frank
     
  16. Darkglass

    Darkglass Gold Supporting Member

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    I so agree with this. Couldn't have said it better.
     
  17. Flux Jetson

    Flux Jetson

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    This is all great, but I think the OP is just modding a store bought pedal, or do I have that wrong?
     
  18. Flux Jetson

    Flux Jetson

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    I still have to insist that it depends entirely on the circuit involved. Certain circuits respond greatly to changing opamps. Others, not so much. In the OP's case, he'll always wonder if it would have done him any good or not if he doesn't at least try. Hence the suggestion to install a good quality IC socket.
     
  19. boomertech

    boomertech Gold Supporting Member

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    Does it matter if it is a store bought pedal or a custom built pedal? I think the information that I provided applies to any opamp circuit, or did I give some bad information? My point was that changing an opamp could make a tonal change within a circuit and the reasons why. I thought that someone understanding why different opamps perform differently or fail miserably within the same circuit is good information to have… especially if they are taking an interest in swapping opamps.


    I never told the OP not to try swapping opamps… In fact, I was the first to suggest an IC socket and have a go at it. I don’t know the Hematoma circuit at all, so I can’t even speculate what the results would be with swapping opamps. I just know from my swapping experience with my TS clone that there was nothing significant, special or mojotastic with the different opamps I tried. I came to the same results as the Visual Sound video. I tried opamp swaps with my RAT clone with the same results, except for nasty phase spikes from an 072 when it hit the rails.

    -Frank
     
  20. DavePlaysBass

    DavePlaysBass Supporting Member

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    Opamps have to matched to the circuit. What are the rails of the opamp circuit? What is the noise figure of the opamp you are replacing and what is the noise figure of the one you wish to replace it. How is the circuit biased. Is their a frequency limiting pole across the feedback network? Is slew rate critical in this circuit. Does offset voltage or offset current have an impact on your circuit. How much gain is the opamp producing?

    Its kind of like buying a good ink jet cartridge designed for a different printer and hoping it will work in your printer.

    In the case of opamps, in the old days most general purpose opamps were not well suited for audio given their inability to slew fast enough particularly at higher voltage levels. This introduced harmonic distortion. Today, we have a lot more options available and if we choose the right opamps for the right circuit, we can make the opamp influcence on tone a non issue. I would assume most people designing "for sale" effects have met the minimum threshold for passing a audio signal and changing opamps is probably going to make things worse or make no discernable difference. With that said, I was bragging years ago about how to upgrade the archaic opamps used in the older G&L preamps.
     
  21. boomertech

    boomertech Gold Supporting Member

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    Excellent point!

    A few years ago I was reading an interview from an engineer at Trident. They started using opamps in their mixing desks when the 741 came out. They would cascade several 741 low gain amp stages to overcome the lack of slew rate to have full bandwidth and low distortion. Even after better opamps hit the market they continued to use the old 741.

    EDIT: Just some advise to anyone wanting to mod a pedal in any way. If your pedal is under warranty and you plan to use that warranty in the future, DO NOT MOD!:D

    -Frank


    -Frank
     

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