Good to see you are still on this. I've had to bow out due to some technical difficulties.
Show us yer board...
You have already seen it! When I get back into my office I can post a picture of the finished unit. As it is sealed I might show the innards after all the test subjects complete their work.
^ It's blinded for obvious reasons. If Ed is *really* thorough, he sends the data off to an independent statistician (not me because I ostensibly know the DUTs and unless you don't want the results until about November ) before unblinding. But this isn't a medical study, so that level of checks and balances is probably unnecessary.
Who are you using for the tests, Ed?
) before unblinding. But this isn't a medical study, so that level of checks and balances is probably unnecessary.Who are you using for the tests, Ed?
^ It's blinded for obvious reasons. If Ed is *really* thorough, he sends the data off to an independent statistician (not me because I ostensibly know the DUTs and unless you don't want the results until about November
Who are you using for the tests, Ed?
After I made the cards for the innards tested them and adjusted things I inserted them. After the test runs I will then open the case.
I will post the rankings and let folks draw their own conclusions.
Basically there are ten inputs with matching outputs at unity in and out. Pads match the gain so should be few unintended clues. All I will comment is there are at least two different circuits under test. I have done a small bit of experimental psychology testing.
Each participant uses the method and the rest of the gear of their choice
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I'm still thinking about this topic.
There is not a good or bad etc simply a statement of second, third and fifth harmonics.
sort of test f of 250, 1000, 3000, 5000, 10000 hz. Or just use one single frequency (but then some mfgrs might tweak for that ).
1/( (2nd dB X weighting2nd) + (3rd dB X weighting3rd) + (5th dB X weighting5) )
A crossover test (if AB out) test similar to Erik Margan Class B test , but still working on that.
I do this manually anyway when evaluating circuits by using a visual FFT.
So some products are needing lowest THD, some need high 2nd harmonic and some require 2+3 mix. The figure of merit simply tells the designer which end of the scale the op-amp is.
There is not a good or bad etc simply a statement of second, third and fifth harmonics.
sort of test f of 250, 1000, 3000, 5000, 10000 hz. Or just use one single frequency (but then some mfgrs might tweak for that ).
1/( (2nd dB X weighting2nd) + (3rd dB X weighting3rd) + (5th dB X weighting5) )
A crossover test (if AB out) test similar to Erik Margan Class B test , but still working on that.
I do this manually anyway when evaluating circuits by using a visual FFT.
So some products are needing lowest THD, some need high 2nd harmonic and some require 2+3 mix. The figure of merit simply tells the designer which end of the scale the op-amp is.
I agree, because I have observe the same by some listening tests.
The main disadvantage of the NE5532 (from my own view) is the fact, that there are two voltage gain stages in the NFB-loop (usual and most used topology in audio op-amps). Inside of the AD797 and the AD825 there is only one voltage gain stage in the NFB-loop. I note always, that this topology is necessary for excellent results while a listening test even in cases, where a discrete circuit is in use (even at power amps).
Some manufacturers in the eighties don't like typical audio op-amps and prefer op-amps for video applications with only one integrated voltage gain stage and an integrated buffer stage in the NFB-loop. The Musical Fidelity is an example (with LM318) - go to the schematic under post #67 - go to
http://www.diyaudio.com/forums/solid-state/59808-musical-fidelity-p170-power-amp-7.html
An other great disadvantage on integrated op-amps is the absence of the possibility to adjust the idle current in each gain stage, especially in the output stage. If I had an OP-AMP in a pentawatt outline like TDA2030 with +/-5VDC and 0,5-1A idle current in the output stage so as the internal topology from AD844 or AD797, it would be an easy task to create a lot of non discrete preamp devices (maybe with an additional jFET front-end in case of a RIAA head amp). Unfortunately until now I have discover such parts.
From the view of measuring results (without listening test) of typical THD values Douglas Self is right. But we all know, the lowest THD-values do not automatically mean great sound.
P.S.: an off-topic question: What difference are between Mark Levinson's "JC-1" and "JC-1DC" - both for use with two 1V5 batteries and both with pottet module but in different size ? - go to
http://www.diyaudio.com/forums/anal...ces-between-mark-levinsons-jc-1-jc-1dc-2.html
Thank you very much for your advices.
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Now I know that the human ear is not particularly sensitive to distortions of low order. Harsh and glassy resp. crispy sound comes definitely not from distortion components below H10.
Rather, such sound character occurs through distortions with a complex character (like in class-B output stages and to large values of Cdom in op-amps amp with two voltage gain stages in the NFB-loop). The human ear is particularly sensitive to distortions with complex character, which is also anywhere showed on the papers of Audio Amplifier Design.
(an image with sine wave and hardly visible very small spikes).
Such kind of distortion don't significant increase the THD value (please note: THD means "Total Harmonic Distortion"), but worsen the sound quality very intensively in all respects except the low frequency area.
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Anyone interested in the "sound" of the opamps, I am inviting you to try my opamp listening test:
http://www.diyaudio.com/forums/everything-else/308514-another-big-opamp-listening-test.html
http://www.diyaudio.com/forums/everything-else/308514-another-big-opamp-listening-test.html
Okay, did it? That was back in December 2016. You ever find out anything?
I would say op amps are remarkable when you look at the engineering. In some ways like a cable opperated gear shift that isn't at all bad. The extra devices allow the circuit to be realised in silicon without large capacitors or whatever. This idea seems to have made amplifier designers think what's good for an op amp is good for a power amp. If a LM1875 perhaps it is. A small example of no real merit for discussion is the Long tail pair tail resistor. I challenged a guy on his simulator to plot how well a tail resistor with capacitor RC filter did against the circuit he intended to use. They on the thread were surprised. I think it ended on him saying surely a transistor is better. One guy came up with a better CCS than him which did win the day. Take which ever side of that you like. He had choices. Ironically a friend disribute a very fine power op amp design called Lab 47 which is dead Bug build. There are arguements both ways. If you were to build a variant of the 1969 JLH class A power amp as an op amp you might well have something interesting. It would ask a lot of you as an engineer and you might need test gear that you need anyway. It would be fun. The distortion would be below what any human can hear and being class A nothing is camoflaged, be it music or fast no repetative waveforms that repetitive sine waves miss ( charging cDom etc ).
MC33078/9 is a nicer NE5532 replacement. It even sounds nice. In SMD it's the same price as LM324N sometimes as the 4 op amp type. If you look it is not as complex as many and has very low > 10 kHz distortion. It's not a super low distortion device, there again nor are we. NE5532 go unstable at the drop of a hat, mostly if you believe the driving 600R claims ( 10 mA is realistic, 25 mA with care ). If you see it happening on test gear you will hear it, look above 40 kHz. You will often find a TL072 whilst not quite working as a constant voltage source is less unhappy ( add a 220R to NE5532 output to mimic that ). Having made sure the NE5532 isn't troubled you might find the sound is much better than you think. It might still sound a bit boring after longer listening, shades of yellow-grey where white is better. Some very fast bipolar op amps have a whiter than white sound, I suspect they are really video op amps. They are expensive and just as hard to live with. One thing I would treasure is SMD to DIL adaptors. I think I have seen them.
MC33078/9 is a nicer NE5532 replacement. It even sounds nice. In SMD it's the same price as LM324N sometimes as the 4 op amp type. If you look it is not as complex as many and has very low > 10 kHz distortion. It's not a super low distortion device, there again nor are we. NE5532 go unstable at the drop of a hat, mostly if you believe the driving 600R claims ( 10 mA is realistic, 25 mA with care ). If you see it happening on test gear you will hear it, look above 40 kHz. You will often find a TL072 whilst not quite working as a constant voltage source is less unhappy ( add a 220R to NE5532 output to mimic that ). Having made sure the NE5532 isn't troubled you might find the sound is much better than you think. It might still sound a bit boring after longer listening, shades of yellow-grey where white is better. Some very fast bipolar op amps have a whiter than white sound, I suspect they are really video op amps. They are expensive and just as hard to live with. One thing I would treasure is SMD to DIL adaptors. I think I have seen them.
Indeed ,opamps are an incredible piece of engineering,but after my experiment of driving my PAs directly from the audio source(see my post in Solid State),I wonder if some "Retro-thinking" is needed.In pre opamp. days (1960s),various circuits were designed for hi-fi.I have an application note from Thorn-EMI, a Mullard pre-amp design,a Goodman's circuit ,and a GE Transistor Manual,all of which use a DC coupled pair,sometimes followed by an emitter follower as a gain block.I believe in the saying: "The more panes of glass,the more distorted the view",it is the same with Audio,the fewer and simpler the stages,the better.As Nigel points out above,opamp.designers have to design avoiding large electrolytics,this involves more stages.The discrete cct.mentioned requires one electrolytic to decouple the emitter of Tr.2,apart from the usual inter stage caps. It is impossible to predict how any amp. be it pre or output, will behave in the real environment,handling the fiendishly complex waveforms of audio,not just the amps. ,but the listening environment.In conclusion,keep it simple and keep the cost down!
Not religious as recently designed in a side-chain using the OP275, there are intrinsic issues with op-amps if used in the signal chain.
Op-amps do excel at intended purpose ie instrumentation, precision gain amplifier, active filters ......
Again, here is the TI engineering note on op-amp internal/external parasitic capacitance effects.
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Op-amps do excel at intended purpose ie instrumentation, precision gain amplifier, active filters ......
Again, here is the TI engineering note on op-amp internal/external parasitic capacitance effects.
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Attachments
Audio electronics does not see a waveform. It just sees a voltage, which varies fairly slowly with time.Alan Frobisher said:
Precision gain amplifiers are exactly what hi-fi audio needs. Other types of audio need signal-modifying amplifiers; opamps plus feedback may be less good at doing this.jfetter said:
simon7000 said he was going to send out 10 sealed op amp amplifiers for listening tests more than a year ago. He also said he could hear op amp differences at a G =10. He has been rather silent about it since then, although it seemed like the intent at the time was to see if people could hear any differences between single op amps at unity gain.
Yeh but at least it wont gather no moss....
Op - amps are fine for audio, i smell no conspiracy here. Is it just because they are cheap/ish
Two problems with opamps:
1. they are cheapish
2. they are designed by engineers using science, and are therefore part of the anti-music conspiracy which brought valves, LP, semiconductors, FM, CD and digital sound into being
On these grounds alone, they should be avoided by all genuine music-lovers.
1. they are cheapish
2. they are designed by engineers using science, and are therefore part of the anti-music conspiracy which brought valves, LP, semiconductors, FM, CD and digital sound into being
On these grounds alone, they should be avoided by all genuine music-lovers.
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