Only that the AD797 does not have input bias cancellation, it does. 900uA per side at an average beta of 150 (yes a new process might have a higher beta or a newer part might have OCD bias current comp or even a trimmed Ib comp) that would be 6uA or for noise purposes 12uA or 2pA/rt-Hz.
I had an ongoing discussion with Jim Williams (RIP) on whether split collector pnp's had any collector to collector noise correlation. I think in the end there is a 20% or so win using them to generate the two Ib comp currents. Such things as lateral split collector pnp's are not available as discretes.
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I don't think so, and I haven't said anything about "propensity for rectifying effects".
What I said is that the TI part appears to be much more prone to collect mains noise through magnetic induction, due to the higher input impedance (compared with the AD797 and the LT1028. I don't see any rectifying effects in PMA's spectra, only mains frequency harmonics amplified. Perhaps I missed some data, though.
I would also reinforce that such a test with 80dB of noise gain doesn't make much sense in a typical DIY setup (dead bug, or even 2 layer PCB with conventional components. This test case is not something that should be treated casually.
Ah, thanks, then why does the AD797 have such a high input bias current (250nA) compared to the TI part (7nA)?
That would be either trim or a lot of circuit sophistry. Just to put numbers on it, ignoring all other voltage noise sources you need 500uA per side bias for 1nV in reality you need at least a little more, that means an Ib comp with a minimum (if it's a max spec) of as much as 100's to 1 reduction.
Just product definition trade offs you can remove the DC error but the noise is still there so for many applications it buys you nothing.
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Scott, what betas are being achieved in the latest processes? I remember Barrie telling me of some experimental heterojunction parts that were running 100k, but I doubt that those are being deployed today --- it would have been big news.
Now if you have to kill me to tell me, never mind.
OPPO. The setup requirs an hdmi connection to get the menu for the setup display. Not good IMO. Spend a little more and have a display window for setup. I couldnt see moving my 60+ plasma TV over to the stereo to read the OPPO menu.... so I had to buy a small 19" TV to get the job done. Would have been fine it this was for the video system.
I put on a TELARC DSD (CD-83488-SA) They call it a stereo hybrid SACD. ?? McCoy Tyner- piano, Stanley Clark on bass and Al Foster on drums. Lots of transients, lows to highs. Sounded really very good! Especially, track #4.
THx-RNMarsh
I put on a TELARC DSD (CD-83488-SA) They call it a stereo hybrid SACD. ?? McCoy Tyner- piano, Stanley Clark on bass and Al Foster on drums. Lots of transients, lows to highs. Sounded really very good! Especially, track #4.
THx-RNMarsh
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I did that, several years ago. ADA4898 is fine!
I think that low input current track might be correct. In the past years I tested many opamps in this circuit and one of badly behaving was OPA209.
Perhaps (but as has been stated), the major factor
is that the bipolars are forward biased, while the
jfets are reverse biased .........
Are you sure that was not beta/Va product? We have some devices with almost unbelievably flat curves, nothing running with 100k beta that I've heard of. The base would be so thin the breakdown would be non-existent.
Well it is primarily a bluray player, so you can't shoot them for expecting a monitor to be plugged into it. You do have an app for it, doesn't that help? The RS232 protocol is also there for old skool users
For us plebs who can't afford a seperate room for the home theatre I suspect it is about ideal.
For those of us who are a little better resourced in modern technology, a cheap PC display with a HDMI input does the job.
Then you can get the desired display in a wide variety of more convenient sizes, for a low cost even if new gear need be obtained.
And I forgot current density is another factor the micro-power op-amps with fractions of a uA Ib can be very bad. Ib comp hides this sometimes, the input stage on a 1nV op-amp rums 750-900uA collector current and uA's of bias current.
Now that you mention it, I do have a new HP touch screen i7 portable of about the same screen size as the little TV. It has HDMI port. Little TV are so cheap now and makes everything PnP. These days, if I have to do any (any) software horsing around to make something work, I dont do. Its PnP or forget it. My time is worth more to me than the TV cost.
I plan to upgrade to UHD 4K soon and will move the OPPO over to it. But there the sound isnt as good so the audio portion will be wasted. BTW, the 4K are fantastic, I got one in my Bangkok place about 6 months ago and love it. At that time I will be looking for another audio only CD player with good performance. Or file server/CD combo. With a menu screen in it.
THx-RNMarsh
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