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Old 18th December 2003, 02:47 PM   #1
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Default Single or Dual opamp package?

Hi,

This may sound stupid but I really can't let it go and I need your opinions.

Let's say I want to build a buffer for my gainclone, leach amp, or whatever amp that I have that has 2 channels (stereo). Would it make a difference if I use 2 single package opamps or just 1 dual opamp provided that my buffer only needs 1 opamp per channel.

I hope this makes sense.

JojoD
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Old 18th December 2003, 03:03 PM   #2
PMA is offline PMA  Europe
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For the highest requirements (crosstalk etc.) use single chips.
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Old 18th December 2003, 03:34 PM   #3
Pedja is offline Pedja  Serbia
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Though they have some shortcomings (for instance you canít use separate supplies), dual opamps give that interesting possibility for better layout of the feedback loop - practically always their output and inverting input are neighbor pins. This might be important.

Pedja
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Old 18th December 2003, 04:21 PM   #4
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I found that using some singles helped with my PCB layout (4-way active LR2 crossover). Being new at this; I didn't want to crowd it much. I also used some physically larger-than-typical caps, so double opamps would've meant more longer traces.
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Old 18th December 2003, 04:38 PM   #5
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most of dual opamps are fabricated completely separately, and some of them specifically say so in the datesheet. so it would surprise me if you can hear a difference between dual vs. 2x single.
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Old 18th December 2003, 04:44 PM   #6
dhaen is offline dhaen  Europe
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Quote:
most of dual opamps are fabricated completely separately,
That may well be true, but the heat from one half affects the other. If you're using a dual, don't use each half for different applications.
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Old 18th December 2003, 07:04 PM   #7
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What do you mean different applications?

1) Opamp A for left channel and opamp B for right channel.
2) Opamp A is buffer for opamp B in high gain.
3) Other configurations?

:)ensen.
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Old 18th December 2003, 09:27 PM   #8
dhaen is offline dhaen  Europe
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Jensen,

I was talking abour using different drive currents from each section, so (3).
So let's say use them for the same mean signal level, and with same load.
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Old 18th December 2003, 09:46 PM   #9
Geoff is offline Geoff  United Kingdom
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Quote:
Originally posted by millwood
most of dual opamps are fabricated completely separately, and some of them specifically say so in the datesheet. so it would surprise me if you can hear a difference between dual vs. 2x single.
It may well be the case that the two op-amps are separately fabricated, but they share common supply rail connections so one op-amp will modulate the other unless they are carrying identical signals.

It is surely far better to use single op-amps where the individual supply connections can be suitably decoupled and isolated so that cross-modulation cannot occur.
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Old 18th December 2003, 09:49 PM   #10
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Quote:
Originally posted by Geoff
It may well be the case that the two op-amps are separately fabricated, but they share common supply rail connections so one op-amp will modulate the other unless they are carrying identical signals.

even if you use singles, they share the same supply rail, or the same mains connection, or the same distribution networks, or the same power plant, etc.

Plus, look at how impressive PSRRs and cross-talk attentuation modern op amps have, .
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