OPA2277 vs. OPA2227

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terjewinther
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OPA2277 vs. OPA2227

Post by terjewinther » Thu Jun 16, 2016 4:10 pm

This might be a detail beyond any interest, but...
Going over my VCOs, I noticed that for some of the CV-summing opamps I have been using OPA2227 and not the OPA2277 noted in the parts list for the module. Should I update to OPA2277 as prescribed, or even LT1013 as the newer version of the build docs list? Or are the differences minor and not worthy to mention?

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terjewinther
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Post by terjewinther » Thu Jun 16, 2016 4:36 pm

Answering my own question here:
After posting I got a bit curious, and went to my studio to check. Right now I am installing 3 of the issue 4 VCOs, but in my other cabinet I have older issue 2 VCOs. So I unscrewed these old ones from the cabinet and inspected them, and sure enough: I had used OPA2227 opamps in them, even though Tony specified OPA2277 opamps even back in issue 2. And these old (issue 2) VCOs have been with me on various possible and impossible concerts, even outdoor festivals, and they have always performed excellently and stayed in tune, so I guess that either version of these "precision op-amps" will do.

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Synthbuilder
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Post by Synthbuilder » Fri Jun 17, 2016 2:55 am

Both the OPA2277 and OPA2227 are 'precision' devices and will work well for the CV summing and expo control circuitry used in the VCO.

The 2277 is pretty much a DC and low frequency op-amp designed for use in power supplies and slow moving precision circuitry. It's ideal for VCO expo use as it is stable and accurate. These days I use the LT1013 as its cheaper and in this application works well.

The 2227 is much faster device and can be used for audio and DC. The extra speed it has over the 2277 won't be noticeable in the VCO as I slow the output of the expo with a rather large capacitor.

If all is well with your modules I'd leave them in there. However, you can swap to the LT1013 and save the OPA2227 for other duties like in a audio mixer circuit.

Tony

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terjewinther
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Post by terjewinther » Fri Jun 17, 2016 5:31 am

Synthbuilder wrote:If all is well with your modules I'd leave them in there. However, you can swap to the LT1013 and save the OPA2227 for other duties like in a audio mixer circuit.

Tony
Thank you. Good advice. I have the opamp in sockets, so re-using them somewhere else is easy.

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