Eric, in the title you asked 'thoughts, anyone?'. But you seem not willing to consider thoughts given. Should we continue this?
jan
jan
I totally agree, it won't be better, and it will be slightly more complicated.
The point of the extra complication: hear the difference between two different opamps, do some experiment with the bunch of TL's I have.
I have no doubt at all, Mr Self design is already optimised, and the most suitable opamp is probably the one he used.
1-I consider the change worthwile as it allows me to hear the difference between two different opamps (specially with the good sounding TL's).
2-I also consider useful to try the TL074 because it allows immediate building since I have them at my disposal, wich is not the case of the NE's
So far downscalling the original design by using les opamps and less powerful opamps has allowed me to buil a totally acceptable headphone amplifier, so this is the third reason that make the change worthwhile from my point of view.
Once the NE5532 package arrives , I will compare the original version of Mr Self to my "downscaled, more-complicated, less-interesting" version. So here I have a third reason that make my new "worsen" design worthwhile : as a learning and testing exercice.
From a purely electronic and technical point of view, I totally agree with Sreten, my experiment is particularly uninteresting and is not worthwhile.
However in real life I am a researcher (not in electronic field of course 🙂 ), so learning and testing are my motto. ( And I am also tired to see the bunch of TL074 just waiting for a "worthwhile" project)
Cheers.
The only way to prove it all to yourself is to build it. In the first instance I would try one TL074 vs one NE5532 and see what the difference in output drive ability is, that is to say the quad package vs the dual.
Considering toughts do not mean to obey or follow mandatory beliefs, it was just an invitation to give an opinion as (almost) everybody understood. I say thank you (again) for all the comments.
I also said that I totally agree with Sreten in some aspects, even if he totally oversimplificated and misunderstood my project he was tecnically right on some points.
I did considered tought from everyone, I can prove it because I answered all the comments. Even from those that did not understand what was my project about.
Mooly did understood, and gave an excelent "tought". I said thank you several times to everybody that gave their toughts. Even to some people that did not understood that I am not trying to improve anything.
Thank you (again) to all those that gave me their opinion; as soon as the NE's arrive, I will build and compare the sound of both amps. In case someone is interested I will post results and impressions here.
PS: if Jan think that I should not build the tl074 amp, then I will not build it ,just to make him feel that I took his tought into account.
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I think - build it but increase the number of TL074s to 48 (from 32) to get better output swing and spread the dissipation out amongst more devices. Also since you say 5W is plenty sufficient, use a step down output transformer to reduce the loading on the OPSs further.
Very good idea, I have an adequate audio transformer, I was wondering about it. Transformers usually gave a warm sound and a soft clipping. Thumbs up for this idea 😀
Are you a hobbist or a pro in electronics Abraxalito?
Ohh no, definitely build it! If you don't, the thought that you passed up a good thing will haunt you till old age ;-)
Jan
I am fully going to consider your advice. See? I care for people that give me their precious toughts. I will remember this moment each minute of my old age years 😀
To satisfy my own curiosity on this I've just tested some opamps. The setup is as follows with each opamp in the package configured as a unity gain buffer. Both dual and quad devices tested all used 3.3 ohm 'balancing' resistors to sum the output. The setup was single rail, AC coupled and driving a 100 ohm load resistor. Level was increased until visible distortion appeared. Supply was 30 volts.
TL084, 13 volts pk/pk
An NEC upC324, 16 volts pk/pk (shame about the visible crossover distortion... Class XD needed 😉)
Texas NE5532, 20 volts pk/pk
LM4562, 18volts pk/pk
Ancient LM833, 8 volts pk/pk with hard +4 limit. Negative going OK to -8 volts.
Modern LM833P with quasi complementary stage 18 volts pk/pk. See following link,
http://www.diyaudio.com/forums/solid-state/274575-about-op-amps-use.html#post4361276
TLE2072, 16 volts pk/pk
OPA2134, 16 volts pk/pk
So there we have it 🙂
Edit... LM833 comparison attached.
TL084, 13 volts pk/pk
An NEC upC324, 16 volts pk/pk (shame about the visible crossover distortion... Class XD needed 😉)
Texas NE5532, 20 volts pk/pk
LM4562, 18volts pk/pk
Ancient LM833, 8 volts pk/pk with hard +4 limit. Negative going OK to -8 volts.
Modern LM833P with quasi complementary stage 18 volts pk/pk. See following link,
http://www.diyaudio.com/forums/solid-state/274575-about-op-amps-use.html#post4361276
TLE2072, 16 volts pk/pk
OPA2134, 16 volts pk/pk
So there we have it 🙂
Edit... LM833 comparison attached.
Attachments
Hi,
Pretty much my point, the TL071x is well known to
be very bad at driving any sort of onerous loads.
Using such a chip for a power amp is a "terrible idea"
as stated by D. Self given all the other chip options.
It can be done, but technically its not an implementation
you would ever choose with a free choice of devices.
rgds, sreten.
Pretty much my point, the TL071x is well known to
be very bad at driving any sort of onerous loads.
Using such a chip for a power amp is a "terrible idea"
as stated by D. Self given all the other chip options.
It can be done, but technically its not an implementation
you would ever choose with a free choice of devices.
rgds, sreten.
Nice, Mooly.
NE5532 is a much abused opamp at an outstanding low price. It's not fully appreciated how a battery of these can produce an outstanding THD+N in a robust structure so economically. Economics is often ignored in audio design, but not everyone takes this point of view, and there is no reason why performance should not approach that achievable with other discrete or IC buffers in a multiloop configuration.
NE5532 is a much abused opamp at an outstanding low price. It's not fully appreciated how a battery of these can produce an outstanding THD+N in a robust structure so economically. Economics is often ignored in audio design, but not everyone takes this point of view, and there is no reason why performance should not approach that achievable with other discrete or IC buffers in a multiloop configuration.
A very simple test but it really brings the point home. I would still rate the TL0's as a very competent device but as you say, and as this quick test prove, its way out of its depth when it comes to current delivery for an application such as this.
Thanks. Yes, the 5532 seems the 'obvious' choice on all fronts, both cost and performance.
Sreten, tl074 were not tested. tl084 were. In science it is dangerous to extrapolate results, even if it seems obvious, it is an oversimplification.
It is also not scientific to make points BEFORE any experiment.
However as a philosophical task you did it well.
Mooly thanks for the useful tests, very instructive. However , the idea was to test two TL against one NE. On a one-to-one match, you make the point in a scientific way :clearly the winner is the NE. The best sounding opamp may remain as an interesting question.
High impedance devices may have a very nice sound.
I would like to say that many, many pro in electronics may say "paralleling 32 opamps is a terrible idea, better use transistors or a more suitable IC". Technically they might be right, but they are also short sighted.
technicians are good, scientists are great, Philosophers are NOT useless.
As a scientist, I apreciate very much your tests Mooly. Thanks for the pictures.
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if you want objective results - lower distortions from several recognized mechanisms then paralleling identical op amps is a poor choice
multiloop with "good for audio" front end op amp wrapping its feedback around designed for high current output device(s) is better objectively on many counts and usually cheaper when board area, stuffing costs are included
even the TL07x series is a pretty good audio input op amp - but its much better to buffer its outputs, possibly add even more loop gain if you understand how to stabilize it with AD837, TPA6120, LT1210..
..they come in packages designed to dissipate Watts of power and can be paralleled inside the input op amp feedback loop too if more current than a single channel is required
I suggest educating your imagination rather than imagining 32x parallel NE5532 is a good idea
multiloop with "good for audio" front end op amp wrapping its feedback around designed for high current output device(s) is better objectively on many counts and usually cheaper when board area, stuffing costs are included
even the TL07x series is a pretty good audio input op amp - but its much better to buffer its outputs, possibly add even more loop gain if you understand how to stabilize it with AD837, TPA6120, LT1210..
..they come in packages designed to dissipate Watts of power and can be paralleled inside the input op amp feedback loop too if more current than a single channel is required
I suggest educating your imagination rather than imagining 32x parallel NE5532 is a good idea
Thanks eric.
Just to point out that the historical difference between TL08x series and TL07x series devices was in lower noise and tighter specs relating to input offsets. That difference seems to have 'disappeared' when looking at current data sheets (and the original devices date back to the 1970's remember). Drive ability between the two is the same.
Now two TL074's (so that's 8 individual opamps) would easily outdrive a single 5532 (2 individual opamps)... if that's what you mean 🙂
Just to point out that the historical difference between TL08x series and TL07x series devices was in lower noise and tighter specs relating to input offsets. That difference seems to have 'disappeared' when looking at current data sheets (and the original devices date back to the 1970's remember). Drive ability between the two is the same.
Now two TL074's (so that's 8 individual opamps) would easily outdrive a single 5532 (2 individual opamps)... if that's what you mean 🙂
interesting concept for sure,
i would wounder how would other people evaulate it, like.. ones who prefer to have a high headroom of available power to have enough to account for 100 dBL dynmic range, or people who prefer to use valves/tubes, and ones who prefer to have amplifiers that have lunatic level of output current.
i would wounder how would other people evaulate it, like.. ones who prefer to have a high headroom of available power to have enough to account for 100 dBL dynmic range, or people who prefer to use valves/tubes, and ones who prefer to have amplifiers that have lunatic level of output current.
Hi,
Just repeat the test with 200R for the TL084 to see if that is true.
The original contention was one TL074 would be better than one 5532.
rgds, sreten.
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Yes, that is what it was all about really and this shows conclusively that its not. The TL074 was swinging 7.5 volts peak so that is what, 75 ma in total or 18 and a bit ma per opamp compared to 100ma (50ma per opamp) for the 5532.