Recommend me a good quad soic opamp ?

[Greg32]

Im building an active 2 way crossover and space is tight so i was thinking surface mount devices but im not sure what to look at in modern devices. Thanks Greg

 

[deandob]

I'm in the same boat - building an active crossover and need more space on the PCB. It has been a while since I investigated the opamp 'du jour'.

Last time I checked it about 8 years back it was LM4562 and a brief search of the 'net shows this IC has fallen out of favour as too clinical and not musical (also a dual not quad).

So I have the same question - What is the latest fashion in opamps?

 

[Mooly]

Do not discount the venerable TL074 (as long as your circuit impedances are not to low). Despite what you may read, the TLO series are capable of truly excellent performance when used for line level circuitry.

OPA1604 is a modern 'audiophile' smd only Quad part.

The 4562 dual opamp remains a personal favourite. Hard to fault this one.

 

[00940]

opa4134. Good old workhorse. Drives correctly lower loads than the tl074 (can be useful for filters), sounds good, forgiving wrt implementation (not faster than necessary for audio), quite cheap, comes in soic14, jfet input makes it easy to implement.

Specs wise, it still holds its own against most newer devices, for audio use at least. Downsides may be highish power consumption and dropout.

 

[OlegSh]

OPA1644, another JFET input op-amp...

Regards,
Oleg

 

[Greg32]

Thanks for the advice and recommendations, i was surprised at the cost here in Australia for an opa1604 or opa4134 they are both in the $8 region per unit. both seem like good candidates and more than capable.

 

[Greg32]

Thanks Oleg, another candidate in the opa1644, specs also look very good.

 

[OlegSh]

Mouser prices for OPA1644 and OPA1604 are the same to a single cent... 5.28 plus the tax, so you have a choice between bipolar and JFET input parts.

 

[simon7000]

The LME49743 is in production but no one seems to stock it. The LME49720 is a dual in stock most everywhere, current production and $3.00 each.

As with all LME types you will need to use a small inductor on the inputs. A 100 ohm resistor with ten turns of wire around it will do.

 

[Greg32]

This xover will be running into a pair of class d boards, i have available dual 5.6v supplies or i can add an extra reg stage for higher rails if need be, any drawbacks using the +-5.6v supplies? regards Greg

 

[DPH]

Should be okay on 5.6 rails.

OPA1644, being JFET input will be more tolerant of your network impedances, but that's not a game-breaker.

 

[jcx]

I've always found duals much handier to layout in active filters

esp with quads and even smt R,C you simply don't have room for better quality R,C parts and good layout with quad op amps and biquad or multiple fedback active filters - maybe with state variable that uses more op amps

some may complain about the "extra" power routing - but then I go 4-layer even for hobbby builds if it needs a PCB at all

 

[scott wurcer]

The LME49743 is in production but no one seems to stock it. The LME49720 is a dual in stock most everywhere, current production and $3.00 each.

As with all LME types you will need to use a small inductor on the inputs. A 100 ohm resistor with ten turns of wire around it will do.

Try getting that on a datasheet. If true that alone would be enough for our guys to obsolete them all.

 

[simon7000]

Try getting that on a datasheet. If true that alone would be enough for our guys to obsolete them all.

I found the issue when building a sensitive preamp. Passing trucks caused it to pin. JC had a tech find adding 100 ohms to the input of a phono preamp cut out RFI. Today he uses the resistor coil to save the noise figure. This has been discussed before and a few other folks have noted the issue.

Way back when you and I discussed this you mentioned the issue could be not enough current in the input stage.

If you would like I can send you some samples.

 

[abraxalito]

What Mooly said. Best bang for the buck by far in opamps is TL074/84 but circuit impedances do need to be kept high for best dynamics. And don't use them to drive cables.

 

[Greg32]

will the tlo74 drive 600r load?

 

[OlegSh]

The THD in the datasheet is guarantied for loads >=2k (see bottom of page 7 of the datasheet). So it may be able to drive 600r load but with significantly higher distortion. If you want to drive 600r look at the newer op-amps.

 

[abraxalito]

It has sufficient output current capability but the max output swing is reduced (5V away from the rails). Definitely not recommended if you care one iota about SQ.

 

[AndrewT]

will the tlo74 drive 600r load?

600r in parallel with what capacitance?
The TL range of opamps do not like any capacitive loading.
I would try to keep the TL loading at, or above 10k

 

[OlegSh]

Why would one first create the problem by using cheap low quality part and then spend more resources solving it? I would just forget about TL074 for this project and use a better/newer op-amp...