Burr-Brown OPA1611/1612 are here

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#21
My samples arrived today FEDEX 3 days after requesting them, USA to the UK. SUPERB.
The paper spec is no more than a talking point, what really matters is the chip in actual use. We can only comment on that with experience of use. I'll post on that subject when I have had time to use and listen to the device.
 
#24
A few of us have built the "Tucson" interchangeable daughter board for the First Watt M2x power amp, using the OPA1611, the OPA604, and the LT1122. The circuit design is ultra simple (figure below).

So far the early consensus seems to be that Tucson-with-LT1122 sounds better than the other two. For what it's worth.

edit- oh by the way, LT1122 is available in PDIP-8 and also SOIC-8, if that's the sort of thing that matters to you.

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#25
Mark Johnson said:
A few of us have built the "Tucson" interchangeable daughter board for the First Watt M2x power amp, using the OPA1611, the OPA604, and the LT1122. The circuit design is ultra simple (figure below).

So far the early consensus seems to be that Tucson-with-LT1122 sounds better than the other two. For what it's worth.

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Click to expand...

Very likely this is because the LT1122 op amps happened to be better “matched”. Otherwise, putting two op amps in parallel without any output ballast resistors is in general considered a very bad idea.
 
#26
No. There are two symbols on the schematic because there are two footprints on the PCB. However the board assembler either populates the DIP footprint, or the SOIC footprint, but not both at the same time. Should you wish to purchase large numbers of blank Tucson boards for experimenting with large numbers of different, non-socketed SOICs, this might be one place to look.

FS: M2x daughter cards, type "TUCSON"

edit- or lay out and fab them yourself, the interchangeable cards are simple and well documented in the M2x amplifier's discussion thread
 
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#27
Mark Johnson said:
No. There are two symbols on the schematic because there are two footprints on the PCB. However you either populate the DIP footprint, or the SOIC footprint, but not both at the same time. Should you wish to purchase large numbers of blank Tucson boards for experimenting with large numbers of different, non-socketed SOICs, this might be one place to look.

FS: M2x daughter cards, type "TUCSON"
Click to expand...

Ok, so electrically speaking the Tucson thing is a simple op amp unity gain buffer. Then I see absolutely no support for the LT1122 “sounds better” claim.

Thanks, but I can build an op amp unity gain buffer myself, if I would need one. I got a bunch of SOIC to PDIP adapters with power supply decouplings for 15 cents a pop.
 
#28
So far, of the people who have built and listened to the simple unity gain buffer made with 3 different opamps, all have preferred the sound of one particular opamp.

It's just anecdotal data; people reporting their personal experience listening to music on homemade gear.

The surprise, if any, might be: that there was any preference at all.

Perhaps a second, smaller, surprise might be: that the preferred sound didn't come out of the whiz-bang slick OPA1611 and its SiGe pedigree.
 
#29
Mark Johnson said:
The surprise, if any, might be: that there was any preference at all.
Click to expand...

Not at all; I would not expect from humans engaging in the effort to do such an evaluation to end up having no preference. That would be, from a psychological perspective, equivalent to a failure or waste of time, not easy to accept for many.

Why people preferred the LT1122 in this particular test run can also be easily explained from a psychoacoustic perspective, but I won’t get into that.
 
#30
Mark Johnson said:
So far, of the people who have built and listened to the simple unity gain buffer made with 3 different opamps, all have preferred the sound of one particular opamp.

It's just anecdotal data; people reporting their personal experience listening to music on homemade gear.

The surprise, if any, might be: that there was any preference at all.

Perhaps a second, smaller, surprise might be: that the preferred sound didn't come out of the whiz-bang slick OPA1611 and its SiGe pedigree.
Click to expand...


Only test instruments can tell them apart really, unless pushed to the noise floor in which case the relatively poor current noise of the OPA1611 would show up at high impedances, as would the relatively poor voltage noise of the LT1122 (showing up at low circuit impedances). Don't use the OPA1611 for a MM phono preamp, don't use the LT1122 for an MC or microphone preamp.... At line level its academic, the post important spec is the price!
 
#32
Jack, I think it would be a good project to lay out a little adapter board which allows an SOIC-8 packaged, dual opamp like the LM4562, to be plugged into a DIP-8 socket for a single opamp like the OPA1611.

There are a few duals that I'd like to try out this way, including LM4562, OPA1656, and (ahem) LM833DGKR, the one not designed by NSC, the one with the all-NPN output stage. NSC's version had a complementary follower output with NPN+PNP.

Mark

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