[Fwd: Re: Op Amp pinouts was Re: [sdiy] more LM3900 stuff]

[Ian Fritz]

At 05:20 PM 1/20/06, Seb Francis wrote:
>Pat Kammerer wrote:
>
>>----- Original Message -----
>>To: Synth DIY <synth-diy at dropmix.xs4all.nl>
>>Sent: Tuesday, January 17, 2006 1:55 PM
>>Subject: Re: [Fwd: Re: Op Amp pinouts was Re: [sdiy] more LM3900 stuff]
>>
>>
>>
>>
>>>>I find that at low supply voltages the OP275 distorts undesirably.  I
>>>>find
>>>>that a much better alternative is the OP270.
>>>>
>>>>
>>>>
>>>>
>>>But at higher supply and signal voltages you might find the opposite is
>>>true - the slew rate of the OP275 is ~10 times the OP270.  The offset
>>>voltage and drift is however much smaller for the OP270 which might be
>>>useful in applications which handle pitch CVs as well as audio.
>>>
>>>Seb
>>>
>>
>>I find that with a +/- 12V supply, the apparent sound quality (by ear) and
>>waveshape (as veiwed on oscilloscope) is better in audio applications such
>>as VCA, preamp, equalizer, and buffer.  I generally use a higher slew rate
>>amp when summing CVs and related applications.  I have trouble beleiving
>>that the slew rate is the primary cause of the distortion that I have
>>noticed when using the OP 275, wouldn't it mostly indicate that a larger
>>bandwidth is possible without loss in linearity?
>>
>>
>>
>What I meant that the fast slew rate should actually reduce distortion for 
>large signals.  There must be other factors that are resulting in you 
>finding distortion on the OP275 relative to the OP270.  Personally I find 
>the OP275s excellent (only used on +/-15V tho) - I tend to use them when I 
>want something better for audio than the TL072.  Or I use the NE5532, but 
>these are kind of current hungry.
>
>Seb

Have you looked at the OPA134?  Distortion = .00008%

   Ian