ash_dac said:
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
Re: So, how does it sound?
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
clem_o said:
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
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
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
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.
I'm definately going to try some of these new op amps, looking forward to hearing them.
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-.
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-.
classd4sure said:
Where'd you get those figures? I missed that in the datasheet(rubbish!)
You'll never find something about that in any datasheet. You have to experiment. The break in time differ from a part to another one. I saw something about that for capacitors but not on op amps.
Some peoples believe on that others not. Make your OPA627 plays for 3 days and tell me the results.
You will probably not like it but it will be different after breaking in time.
legarem said:
Hi Marc,
It is highly unlikely that the shy bass comwes from the opamp. Possibly your input network contains a coupling cap and/ resistors, normally this determines the bass response. There could be interaction between this input network and the opamp input impedance, depends what you had in there before.
Shy bass generally points to more exact reproduction as most 'warm' bass is caused by freq doubling in the woofer and/or filter effects in the (op)amp input network. So this opamp may provide better control and therefore appears to be bass shy due to lack of coloration.
Also note that almost any opamp has a very, very high gain and extremely good control at low frequencies. Opamp differences are generally in the higher frequencies. If there is a difference in lf reproduction it is almost always due to other factors.
Jan Didden
janneman said:
Hi Jan
The output of the TDA1545 goes directly in the LM4562.
You're probably right about control and lack of coloration.
The OPA2604and OPA627 'seems' to have more bottom end but it is probably due to the laid back presentation of the BB chips. (recessed mids and highs means more bass) The LM4562 reproduces more détails hidden by the others.
V+ and V- being decoupled with tantalum caps paralleled with ceramics, I will perhaps try Black gate caps to replace the tantalums which can perhaps cause an overbright sound.
Marc
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