LM4562, LME49710, LME49720 Start-up Behavior

[mediatechnology]

I agree that the unequal loading with the 2072 looking at one leg is marginal at best.

I wonder if when powered down, the balanced input op amp would produce sufficient AC (steered from input) on it's Vcc, Vee or output pins that could be detected by an AC-coupled always-on NJM2072.
The 2072 would then bootstrap the rails for the balanced input and switch on the following stages.

The 2072 is isolated from the inputs, only one 2072 is needed for a balanced input, and the input stage can also be powered down.
Through the supply pins the external or internal diode thresholds might prevent it from turning on at a low enough level but the 2072 has gain.
For a balanced input there might be enough current through the input and feedback resistors with the op amp off to make it to the output and NJM2072.

Just a thought...

[carlalex]

I don't know the model number but hear that Bruno also makes a plate amp version of the hypex amp with a DSP built in , so that would be mission designed and cover the crossover with even more capability.

I've designed analog crossovers and there are things that digital just does better (like delay).

I think I've seen those. They looked slick. I don't really have a convenient way to drag a digital signal to each speaker. What consumer receivers even have a per channel digital out? A to D back to A may work, and may work quite well in practice, but seems like a hack to work around not having what you would really want - digital straight from receiver.

Also, being a software guy, I've never really liked what appears to be windows only software as an afterthought which seems to be required to configure these. Will I even be able to program it in 10 years? From my Linux machines today?

As for delay, I think I'm passing on trying to deal with that in version 1 of this project. It's a gold plated project, not platinum I figure if I want to tackle that in the future, it would just come down to a board upgrade. Digital could be done that way too, for that matter. Power amps and the drivers would be the same in these cases.

--- Carl

[mediatechnology]

viewtopic.php?f=6&t=641&start=25

I just checked this with a powered down THAT1240.
With a high impedance load, low-level signal passes through at essentially unity gain from balanced input pins to output pin.
With a 1K output load, signal is attenuated by about 26 dB - still enough considering the gain of the NJM2072.
I've got a 47 R between the supply pins - below the drop of the ESD diodes signal passes through the part with what appears to be only resistive termination.
As long as it's below the ESD diode forward drop, the surrounding op amp, when powered down, appears to be fairly high impedance.

[JR.]

If the input signal is coming from a HIFI receiver it isn't balanced anyhow. Maybe wire it up impedance balanced but unless you know the source impedance of the receiver that probably isn't worth the trouble. Keeping the signal 0V separate from the shield probably is worth the trouble.

Hanging the 2072 on a differential input may not hurt it all that much.

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back in the day we used all-pass filters to make short delay's to compensate for driver physical alignment in active crossovers.

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have fun... melt some solder, you'll figure out soon enough what is what.

JR

[JR.]

It appears that TI has just set an EOL date of late next year on these.

Perhaps more problem calls than sales...

JR

[mediatechnology]

It appears that TI has just set an EOL date of late next year on these.

Perhaps more problem calls than sales...

JR

TI? or Japan Radio?

[JR.]

TI

http://e2e.ti.com/support/amplifiers...s/f/6/t/457875

JR

[mediatechnology]

https://e2e.ti.com/support/amplifiers/a ... 6/t/457875

I'm not sure this is a great loss.
The 36V LME49720 may be EOL disco'd but if the 44V LME49860 is still active that's even better.
If the LM4562 is still around then the LME49720 effectively is.
The LME49710 is a single and for my money you still can't beat the 5534 now sourced only by JRC as the NJM5534D.

EDIT: Forgot TI still? makes the NE5534...

In low-level apps I found these parts to be noisy.
The burst noise was a problemo and the low Ibias not worth the noise.

[JR.]

I won't miss them because I never used them...

JR

[carlalex]

Bummer. Although, it seems from the announcement that was posted that the LME49720MAX is the designated replacement; Wonder how long that will stick around. No replacement for the single opmp version, which I was actually planning to use over a package with an unused opamp I'd have to power.

No through hole version for the listed the replacements. Wonder how long the NJR part will stick around.