John Curl's Blowtorch preamplifier part II

[wrinkle]

Remarkable part

LOL

 

[hitsware]

LOL

HA!...HA!...HA!....
~ 20 V/uS compared to 0.5 V/uS
Puts it within Jungs criteria for audio use .....
HA!...HA!...HA!....

 

[john curl]

Yes, Hitsware, but look at the 'small print'. It is vastly better than the 741 in rise-time and slew-rate, but disappointing in actual performance BELOW SLEW RATE. This is WHY Otala did not like to use slew rate as the dominant criterion. (I don't necessarily agree with him on this)

 

[john curl]

OK, PMA, what were you doing in 1969? Out of school yet?
That is when Matti Otala wrote his first paper for the IEEE Audio and Acoustics group.

 

[DavidL]

*Yawn* yet more ancient history drivel get on with the measurements already or am I wasting my time here expecting to see any?

 

[hitsware]

Yes, Hitsware, but look at the 'small print'. It is vastly better than the 741 in rise-time and slew-rate, but disappointing in actual performance BELOW SLEW RATE. This is WHY Otala did not like to use slew rate as the dominant criterion. (I don't necessarily agree with him on this)

I got the impression from some of the comments that the 'S' was considered
meaningless .... Far from it no matter the small print .....

 

[vacuphile]

About what? All I did was post links to data sheets.

You are wrong at a far more transcendental level; there where the fairies live. In that land, you are the biggest lier of them all.

 

[Steve Eddy]

*Yawn* yet more ancient history drivel get on with the measurements already or am I wasting my time here expecting to see any?

Rhetorical question?

se

 

[scott wurcer]

Yes, Hitsware, but look at the 'small print'. It is vastly better than the 741 in rise-time and slew-rate, but disappointing in actual performance BELOW SLEW RATE. This is WHY Otala did not like to use slew rate as the dominant criterion. (I don't necessarily agree with him on this)

Slew enhanced op-amps are an obscure backwater of basicly useless technology, we learned that soon after they were proposed.

 

[john curl]

Now, David L has actually asked a valuable question as to how we can get the same 'results' from modern test equipment as we got with the relatively 'old fashioned' AD524 IN-AMP with 'modern' test equipment? Personally, I don't yet know, because of the limitations of the 'modern' test equipment as I find it. Perhaps an analog differential subtraction test would be useful to get an error signal, that then could be further processed. In any case, DA is real, and it can generate real problems with certain common audio signals. Ignore it at your own risk.

 

[john curl]

Oh, and how many millions of dollars were invested into inventing and producing them?

 

[john curl]

Of course, there are other 'defects' in capacitors other than static distortion or DA. This is where vibration sensitivity, and Q comes in. That would be an interesting test, and even MODERN test equipment might help us there.

 

[scott wurcer]

Oh, and how many millions of dollars were invested into inventing and producing them?

As these things go not much. Please show me one successful audio power amp that uses slew enhancement to get a "good" slew rate number while still being a low GBW amp underneath. This is just a sideshow.

 

[hitsware]

> Slew enhanced op-amps are an obscure
> backwater of basicly useless technology,
> we learned that soon after they were proposed.

If the value of compensation cap(s?) in a 5532
is altered so that it becomes a 5534, isn't
that 'slew enhancement' ?

 

[john curl]

By this definion, 'slew enhancement' is a fundamental restructuring of the input stage to keep it from input current limiting on transients.

 

[john curl]

Oh, then Matti Otala was right to not JUST look at slew rate when measuring amp performance? Thought so.

 

[hitsware]

By this definion, 'slew enhancement' is a fundamental restructuring of the input stage to keep it from input current limiting on transients.

Degeneration ?

 

[john curl]

No, more than that.

 

[keantoken]

That cap test is interesting, I think I could actually do that with my old Tek 561B with it's 10uV/1MHz differential amp and my SG504. I don't think resistor nonlinearity could be a problem, could it?

The MC7xxx regulators by OnSemi (I believe MC parts were from Motorola formerly?) are actually better than the LM-based parts based on the datasheets, maybe they improved it? That was an unrelated thought when I saw the MC parts earlier.

On caps, have they developed a way to make thinner MKT films? I complained at Digikey for having a 3.3uF Epcos cap for 5mm pin spacing, very cheap, and they corrected it by using a newer datasheet. WIMA even has 10uF MKT's with 5mm spacing and I got a few of those. The specific cap was the B32529 from Epcos - it seems to be the cheapest uF range MKT for 5mm pin spacing. The only reason I didn't get a bunch was because the DF specs seemed to show unusually high ESR.

Concerning "special" capacitors, I'm surprised no one has brought up the Kemet R73, film/foil MKP. Also the Kemet PFR (although just very small capacitors). Formerly Evox-Rifa, which Kemet aquired. There seems to be a conspicuous stigma towards Kemet.

 

[DavidL]

Now, David L has actually asked a valuable question as to how we can get the same 'results' from modern test equipment as we got with the relatively 'old fashioned' AD524 IN-AMP with 'modern' test equipment? Personally, I don't yet know, because of the limitations of the 'modern' test equipment as I find it. Perhaps an analog differential subtraction test would be useful to get an error signal, that then could be further processed. In any case, DA is real, and it can generate real problems with certain common audio signals. Ignore it at your own risk.

Actually I was asking you when you were going to stop driving down memory lane and post something new instead but frankly I give up. Have fun living in the past, this thread is useless.