Quad Op Amp for Audio

[Grant Richter]

The noise figure for op-amps is an important issue for audio.
The 741 type op-amp has a huge 35 nv/Hz figure.
Fairchild RC4136 is in the 10 nv/Hz range.
NE553x is in the 5 nv/Hz range.
Anything below 20 nv/Hz is usable for +/-15 volt supplies and
+10 dB (10 v peak to peak) signal levels.

Another significant factor is slew rate.
741 has a control voltage only 0.5 volts/microsecond slew rate.
Most audio op-amps have much better figures between
2 to 13 volts per microsecond.

Input bias current and offset voltage are not so critical for
audio, but it would be nice if they were small.

The TL074 quad op-amp has a noise figure
in the 10-15 nv/Hz range, 13 v/microsecond slew rate,
JFET inputs for microscopic bias current,
20 millivolts offset and costs $0.60

Do not use them for building guided missiles as they do
not like to operate at 125 degrees C (input leakage
currents go up significantly over military temperature ranges).

The RC4136 has a non-standard pinout and is not recommended
for that reason.


----------
> From: inman at interpath.com
> To: synth-diy at mailhost.bpa.nl
> Subject: Quad Op Amp for Audio
> Date: Thursday, September 02, 1999 9:32 AM
> 
> I am looking for suggestions for a standard QUAD OP AMP for
> audio signals.  I guess what I need is a high speed, low noise OP 
> AMP, hopefully not too expensive.  I have been using an LM837 
> which works well.  Is there something better that is not 
> extremely expensive?
> 
> Thanks,
> 
> Elliot
> 
> PS.  In Electronic Projects for Guitarists, Craig Anderson uses a
> dual op-amp, the NE5532.  I assume this is a very good chip
> (cost $1.20 from digikey).  He also uses an XR4136 quad, but
> I cannot find that.