OP Amp Substitution - for audio

[Tony]

I have a old stereo preamp that uses a LH356 op amp can I substitute a Burr
Brown OPA134 to improve the quality ? The specs for the OPA134 are quite a
bit better and is pin compatible. Any suggestions...

Thanks
Tony

 

[Kevin McMurtrie]

I have a old stereo preamp that uses a LH356 op amp can I substitute a Burr
Brown OPA134 to improve the quality ? The specs for the OPA134 are quite a
bit better and is pin compatible. Any suggestions...

Thanks
Tony

It depends on how the op-amp is being used. Op-amps are nearly perfect
devices as long as they're operated well below the gain versus frequency
curve. Get too close to the open loop gain and that's where one op-amp
can be vastly superior to another.

I can't find any specs on LH356 or LM356 but it's mentioned as audio
grade JFET input, the same class as the OPA134. You shouldn't have any
problems swapping the op-amp.

 

[Winfield Hill]

Kevin McMurtrie wrote...

... I can't find any specs on LH356 or LM356 but it's mentioned as
audio grade JFET input, the same class as the OPA134. You shouldn't
have any problems swapping the op-amp.

The part Tony is thinking of is the National Semi LF356 (note the F).

-p/n- f_T slew gain Iout noise Cin
----- ----- ------ ----- ---- ----------- ----
LF356 5MHz 12V/us 106dB 15mA 12nV/Hz^1/2 3pF
LT1056 6.5MHz 16V/us 112dB 25mA 15nV/Hz^1/2 4pF
OPA134 8MHz 20V/us 120dB 35mA 8nV/Hz^1/2 5pF

The National Semi LF356 is a respected venerable opamp. Linear Tech's
replacement parts, the LT1056 and LT1057 (dual) are my favorite jelly-
bean JFET opamps. But, yes, the OPA134 looks a little better from
these specs. And they specify audio-range distortion - a nice touch.
But I'll stick with the LT1057's lower input-offset voltage. :>)

Thanks,
- Win

whill_at_picovolt-dot-com

 

[Tony]

Thanks guys

regards,
tony