Bob Pease on the New LM4562

[paulb]

Originally posted by janneman
TI is not to be outdone:

http://www.ti.com/corp/docs/landing/...able+PA+opa365


Jan Didden

OPA365 is a 5V part. Need more swing.

[jan.didden]

Originally posted by paulb

OPA365 is a 5V part. Need more swing.

True, but it is great alternative for 5V systems like DACs and DSP's where supply normally is 5V or even lower.

But what amazes me always that they again and again outspec the competition (and themselves). What will it be in 10 years? 1pV noise and 0.000000001% THD??

Jan Didden

[BrianDonegan]

Probably, but they will also run on .0025V rails

[ash_dac]

Hi,

The LM4562 datasheet notes a settling time to 0.1% of 1.2us. I couldn't find any settling time graphs on the datasheet. Has anyone managed to find them ?

[Russ White]

Originally posted by ash_dac
Hi,

The LM4562 datasheet notes a settling time to 0.1% of 1.2us. I couldn't find any settling time graphs on the datasheet. Has anyone managed to find them ?

Hello,

Just a general note to all, not necessarily an answer to your direct question.

1.2us seemed sort of high for an opamp of this quality, so I called National to get the scoop. It turns out that the data sheet does not tell the whole story.

You need to remember that this data sheet was written with audio apps in mind, and as such they provide some of the metrics against less than ideal op amp loads. For instance the settling time is measured into a 100pf load. That 1.2us looks high until you figure that in. If you measured most other op amps into a 100pf load you would see much much worse response. Load capacitance has a very negative effect on settling time. I think national was trying to show that even into the very tough load the settling was still quite good, and it is.

On other op amp datasheets you will almsost never see the settling time measured while driving a capacitive load.

I am actually hoping National will revise the data sheet and show settling time for both a non-capacitive (like other data sheets) and the capacitive load.

Cheers!
Russ

[legarem]

Originally posted by clem_o
For those who have samples - please give feedback on the sonics of this part, if possible!!

Cheers!

Clem

This spring, I bought a MHDT Labs Paradisea Non OS dac. The I/V conversion was made with an OPA2604. I changed it for a DIP socket with Brown Dog adaptors with two OPA627. The sound was way better but the laid back sound with the BB never ceased to bog me.

The LM4562 was installed and the player was placed at repeat for 1 day before I decided to listen it seriously.

The 'new' sound is quite a shock. Excellent bass control, micro details are there so I now hear things on cd I was not hearing with OPA627.

Harmonic extension on piano notes, sax etc is simply fabulous. No laid back sound with good rearscape. Image is very good.

I'm still surprized about what this op amp do. It is not euphonic. Those who love vintage sound with bloated bass and soft treble will not probably like it. It is real, sound direct, is not sounding hard at all. A truely new standard in op amps.

The OPA627 has veiled sound if you compare it to the LM4562. Best is that the added details with the LM do not add harness to the sound.

I hated op amps in audio but this one will probably help to change my mind.

Marc

[Spev]

I received some samples of the LM4562 yesterday and am thus far very impressed. I've tried most of the usual suspects thus far and this beats all. As with the previous poster, I'm hearing details I didn't know were there - decaying vibrato on voices that was previously hidden, creaks of people moving on seats, cups of coffee hitting the mixing desk....

One question though, the chips have been dropped in the below circuit as direct replacements for the original TL072s.

Line Amp

The differences in my circuit are i have 47k resistors instead of 27 in the feedback position and have 100pf polysty caps in parallel to filter hf. The mute and balance circuits have also been removed.

Any values I should change anywhere to get the best out of this opamp?

ta

James

[classd4sure]

I tried opa627's over the weekend. They lasted all of 10 full minutes in my system.... got to be the most fake sound I've ever heard. Pure garbage. They probably measure very well but whoever thought of marketing them for audio was on drugs.

I'm definately going to try some of these new op amps, looking forward to hearing them.

[legarem]

James

I don't think that you have to change something in your circuit.

The LM4562 is a high speed op amp. To have good or best results, you have to decouple the V+ and V-

I placed a 10mfd tantalum paralleled with a 0.1 ceramic between V+ and gnd and other ones between V- and gnd. I also placed a 1 mfd polypropylene between V+ and V-.

[legarem]

Originally posted by classd4sure
I tried opa627's over the weekend. They lasted all of 10 full minutes in my system.... got to be the most fake sound I've ever heard. Pure garbage. They probably measure very well but whoever thought of marketing them for audio was on drugs.

I'm definately going to try some of these new op amps, looking forward to hearing them.

You can't judge so fast. The OPA627 must be broken in at least 3 days before it will reach it's potential.

The LM4562 took less time but it needs a minimum of 1 day