My recommendation, regarding limiting of input SR for 4562, was based on measurements I made several years ago. I was testing various opamps with steep input square, pushing input differential stage into non-linear region. It happened that I partially destroyed several 4562 opamps. They were still working after tests, but Vos (offset) was increased and distortion higher.
Absolutely same test made no harm to JFET OPA2134.
Absolutely same test made no harm to JFET OPA2134.
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I said a lot about caps a few months back here in this forum already.
I presume one could beg, borrow, rent or steal what they needed and find someone/audiophile who owned the product of interest and would loan it for testing. yes/no/maybe? I was not suggesting go out and buy everything !!
Thx - RNMarsh
I think you are a little too "definitive".
Audible distortions (harmonic, intermodulation, phase modulation), in a open loop amplifier depend greatly on the ratio signal slew rate / amp slewrate in a closed loop.
It is some kind a decreasing exponential curve. So, faster the transmission in the loop, better it is.
There is no point where you can say: "that's enough".
I don't talk from some readings, but weeks of listening experiences and measurements on this subject.
And i don't see why some could refuse to spend 10 second to test an other OPamp, it is so easy to change them on a socket.
Make your own opinion by testing, not believing.
???
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john curl said:
If I may be permitted my $0.02 ..
LM4562 is one of the new uber OPAs with ultra low THD & zillion V/us slew. It suffers from something like the latching behaviour of TL07x so is contraindicated in certain types of active filters and also simple single supply applications. In the former, overload results in particularly nasty sounding behaviour. In the latter, its prone to latch on switch on and not come up.
What IS interesting is NJM4562 which in most audio applications equals LM4562 for ultra low THD, PIM, zillion V/us & other Golden Pinnae attributes and often surpasses it eg lower noise. It does this without the nasty latching which is LM4562's Achilles heel and is generally very well behaved.
The interesting bit is that NJM4562 doesn't use the LM4562 topology but that of ... 4558!
If JC feels icky about comparing Blowtorch with evil 4558, perhaps NJM4562 might sweeten the pill ... sorry gentlemen. Couldn't resist _____________________
OPA2134 is sorta a better TL07x without its nasty latching behaviour. Very good THD, even compared to the newer uber OPAs in REAL applications.
But it's real strength, and its a HUGE one, is it's input circuit gives it immense immunity to RFI. This really comes to the fore in domestic unbalanced stuff where we can't take the precautions we can with professional balanced i/ps.
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Pavel, in the slew tests which damaged LM4562, was this with voltage followers? Did you overload? Trying to figure out if the input LTP was taken out of its CM range or if this happens without overload.
The degradation you notice is usually cos Vbe on the input devices has Zenered. A quick sign that this has happened without digging out your multimeter or AP is the noise level will have gone up a lot.
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ticknpop, I'm sorry my contributions do not have the clarity, accuracy and usefulness of JC's sermons. I'll try harder next time.
I was unaware that being an 'established designer' exempted you from telling the truth.
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kgrlee,
I am afraid the NJM4562 (on old design) is worlds away from the LM4562 - distortion (c. 50ppm at 3V out at 20kHz) and bias currents (100nA typ, 500nA max) for one are very high. the LM4562 manages sub 1ppm into 600 Ohms under similar conditions and the bias current is typically about 10nA.
And the slew rate on the LM4562 is not zillion V/us - its about 20 V/us.
And no, they dont latch up either if you use them within their specs.
Pavel - clearly you exceeded the CM input range on the LM4562. JFET op-amps are often a bit more tolerant of this trype of abuse.
I am afraid the NJM4562 (on old design) is worlds away from the LM4562 - distortion (c. 50ppm at 3V out at 20kHz) and bias currents (100nA typ, 500nA max) for one are very high. the LM4562 manages sub 1ppm into 600 Ohms under similar conditions and the bias current is typically about 10nA.
And the slew rate on the LM4562 is not zillion V/us - its about 20 V/us.
And no, they dont latch up either if you use them within their specs.
Pavel - clearly you exceeded the CM input range on the LM4562. JFET op-amps are often a bit more tolerant of this trype of abuse.
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But it's real strength, and its a HUGE one, is it's input circuit gives it immense immunity to RFI. This really comes to the fore in domestic unbalanced stuff where we can't take the precautions we can with professional balanced i/ps.""
I dont think so.
There are plenty of bip input m/c head amps around that that I am not hearing a lot of RF pickup complaints about. Screen and earth well and most of these problems are a non-issue. Of course, if you live next to a 10kW AM transmitter . . . move. Its probably not good for your health anyway.
I dont think so.
There are plenty of bip input m/c head amps around that that I am not hearing a lot of RF pickup complaints about. Screen and earth well and most of these problems are a non-issue. Of course, if you live next to a 10kW AM transmitter . . . move. Its probably not good for your health anyway.
We had a radio ham club in our campus building in TIASUR back in 1970'th, on the top 9'th floor. During competitions lights in the building were dimming in tact with duck cracking AM demodulation of SSB happening in turntables and tape recorders. However, according to regulations the top power should be no more than 200W, but I am afraid they were taking from their GM-70'Th some more...
No screening, shielding, filtering, other passive defense helped. Only jamming of ham bands. Active defense. Only then we could silence them.
No screening, shielding, filtering, other passive defense helped. Only jamming of ham bands. Active defense. Only then we could silence them.
You might be missing the point. Sharp spikes are coming with signal from many digital sound sources as a residual of fast digital circuits function. They may be small in amplitude, but with very short rise time and are difficult to suppress. The other source of spikes is a switched power supply. All of these comments of mine are based on real-life measurements.
Exactly.May-be one of the reasons why some people find everything digital a little too" shiny" ?
I had tried a lot of OP amps. Unsatisfied until i used OP260.
A 90Mhz 1000V/µs with a noise factor of 5nV/√Hz and 20ma of available output current.
I chosen this one because its optimum feedback resistance was 2.5K, and still Ok at 10Ko, easy for any existing circuit in Audio.
Used everywhere in my set-up, and specialy at the output of all DACs, my system became totally "fluid", involving and transparent with solid "fast" basses. All harshness disappeared and amazing dynamic
Some can says it is overkill ? It is easy, not expensive, and just deserve a test.
I will not enter in any controversial discussion about the following, consider-it as a totaly subjective remark, but i have always found that current feedback topologies bring something very natural and fluid in the sound reproduction texture. And many others who had tasted to it report the same and never go back.
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Apologize for the incoherency of my post, probably due to my poor English and lack of intelligence. Please, note this is perfectly coherent.
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