Best drop-in op-amp upgrade for 353?
Edward Lipman
Could anyone share their thoughts on the best drop-in upgrade
vis a vis noise for an LF353?
I am torn between the OP275 and the OPA132 or OPA134.
TIA --
Edward
Norbert Hahn
Edward Lipman <EW...@CAM.AC.UK> wrote:
>Could anyone share their thoughts on the best drop-in upgrade
>vis a vis noise for an LF353?
I don't have the specs of the LF353 here in my office but I assume
it is a JFET input amp.
>I am torn between the OP275 and the OPA132 or OPA134.
Both the OP 275 and the OPA 132 (2132 and 4132) are decent audio
amps but are designed for different purposes: The OP 275 is a bipolar
amp while the OPA x132 has a JFET input. The OP 275 can be used
in a very low impedance environement only but has considerable less
self noise there compared with the OPAx132 (which in turn has less
noise than the good old OPA 604).
If the circuit layout isn't clean you may get some overshoot or even
oscillations when using the OP 275 in low gain applications. Use a
scope to check this.
So you may be better off using the OPA 132.
Note that it will not work properly if the supply voltage exceeds +- 15 V.
>TIA --
>Edward
Hope this helps,
Norbert
Miguelito
In article <5o3srh$mfv$1...@news.th-darmstadt.de>,
Norbert Hahn <ha...@hrz.th-darmstadt.de> wrote:
>...
>So you may be better off using the OPA 132.
>Note that it will not work properly if the supply voltage exceeds +- 15 V.
I think that the supply voltage for the OPA132 series can go all the way up
to +-18V. All measurements that appear on the specsheet were done at +-15V
supply voltage though (unless otherwise noted).
OTOH, the OPA604 series can run all the way up to +-25V.
Miguel
Edward Lipman
If money were no object, would something like a 2711 be even better?
Edward
Monte P McGuire
In article <33A0B2...@CAM.AC.UK>, Edward Lipman <EW...@CAM.AC.UK> wrote:
>Could anyone share their thoughts on the best drop-in upgrade
>vis a vis noise for an LF353?
Without looking at the circuit, it's really not so simple to say which
of the chips you mentioned will have the lowest noise. If the
equivalent impedance at each op amp input is below 5K ohms or so, the
OP275 may be a bit quieter than the OPA2132; the venerable and much
maligned NE5532 will be even quieter and have less distortion than the
OP275. However, for source impedances greater than 10K, the OPA2132
will undoubtedly be quieter than any of the chips mentioned.
As for other issues, the OP275 seems to be a little finicky with
marginal layouts, so be careful to check for oscillation if you use
it. The OPA2132 IMHO is the best sounding of the amps you mentioned
and also the easiest to apply, if you want a clean amplifier. If you
want to retain some of the LF353 sound but reduce the level of
distortion a bit, the AD712 is a good choice. The 712 doesn't have
the low noise or high output drive that the 275 or 2132 have, but
sometimes those things don't matter.
As for the 134 (or more accurately, the 2134 dual version), it doesn't
seem to spec as well as the 132 series, even though it's supposedly
designed for audio. The THD curves for the 132 look a little better
at HF than the 134...
The OPA2604 is also a reasonable choice too, although it draws more
supply current and has slightly worse distortion characteristics than
the 132 series. It also requires a few minutes to warm up before it
sounds or specs well. However, it can be used with much higher supply
voltages than the 132 series, so it may be desireable for your
circuit.
BTW, what circuit is it that you're modifying??
Regards,
Monte McGuire
mcg...@world.std.com
Edward Lipman
Monte P McGuire wrote:
> BTW, what circuit is it that you're modifying??
First, thanks for all the info.
It's really several circuits. First, input stage of headphone amp
feeding class-A transistor tage from unablanced source.
Then, a TL074 and two 5532s in a pro matching box to comnvert unbalanced
to balanced. The TL074 is first in the circuit, then one 5532 per
channel. It has some noise in the circuit (I am running it at +12db) and
I thought replacing the chips might help a bit.
Lastly, LF353 are specced in so many circuits one builds I was hoping
there was a good, all-round chip to replace it -- within reason cost no
object. There seems to be a beautiful Harris chip (HA-5222) but that is
beyond my price no object category at $45! However, a gentleman is
kindly sending me a sample and I'll be interested to hear if there is
any audible difference.
Any opinions on the OPA2711 and OPA2707? Use of OPA404 as a quad?
TIA,
Edward
Jon M. Risch
The OPA404 makes an excellent quad replacement chip for the AD-713, or
the ubiquitous TLO-84. Not many choices in decent quads, make a header
and drop two OPA-2604's in instead. My next choice would be the OP-249,
or try an AD-746 but check for oscillations due to the raw speed of this
chip!
My favorite drop-in dual is the BB OPA-2604. See the "AD-712" posts in
this newsgroup for details. One comment on the Harris chip: watch out
for some of the "ultra-fast" IC's, they can be all too prone to
oscillation in drop-in situations (like the AD-746), or draw so much
current that they muck with the
power supply situation.
Jon Risch
Jens Bager
> Monte P McGuire wrote:
>
--
--
> Then, a TL074 and two 5532s in a pro matching box to comnvert unbalanced
> to balanced. The TL074 is first in the circuit, then one 5532 per
> channel. It has some noise in the circuit (I am running it at +12db) and
> I thought replacing the chips might help a bit.
> --
As the signal passes an TL 074 first, there is no reason for
super-lownoise, expensive devices. Try to replace it with a TL 072 ! It's
old fashioned, and less prone to self oscillation than the LF 353, and
it's less noisy and cost only a little more.