| Asbjorn |
Hi!
I'm from Denmark and is working on a highend preamp sparetime project.
I've been doing some listening tests of jfet vs bipolar transistors, and found some generel sound differences.
Jfets tends to sound softly, while bipolar sounds more dynamic.
Do you have any experiences like this, and which do you think sounds the best?
Regards
Asbjorn |
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| DrG |
| Both can be made to sound excellent in a well-designed circuit. The JFET would be more forgiving in a low/no feedback application I think... Chat to John Curl... he's very well versed on things of this nature. |
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| richwalters |
You should be able to get the noise level equal to standard bipolars or better. Jfets provide an easy opportunity as a voltage controlled resistor (VCR) for channel selection without clicks.
When the bias points are properly selected, the low noise of high gfs junction fets is obtained.
The fet is voltage operated while the transistor is current operated, so FEts have a lower noise current. They should be preferred in audio appls where now noise is a requirement but not always. The industry standard IC 5534A bipolar is still used practically in most studio consoles mic/ line interfacing circuits. One point to watch out with fets, they are basically RF devices and will "take off" with bad layouts.
I adore them, as a Jfet is in many ways similiar to a triode.
Fets have very high dynamic range greater than 100dB with very low IM distortion products.
Go for it.
): rich |
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| Asbjorn |
Actually I believe jfets sounds alot more like triodes than bipolar too! But this smooth, soft and nice sound it delivers - is it correct or some kind of "coloration" that's being added to the original signal? I'm afraid it is!
Btw, I think ne5532 is better than those popular fet opamps from AD and BB. I think all the AD and BB opamps I've heard sounds bright and undynamic comparede to ne5532, which is really the only opamp I know with good dynamics from 500hz and downwards (sonically). Also it is more detailed, but it is detailed in another way than the AD and BB's. It is detailed in a way like the sounds coming from the real world are; you really don't hear them - they just are there! With the AD and BB opamps there is some kind of "focus" on the details, and they therefore sound more detailed at first, but really the details are seperated from their natural context - at least that's what I think! :smash:
But what do you think about jfets and bipolars? Especially sonic experiences have my attention.
:) |
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| richwalters |
from the pit......When I was in audio some years ago, the little thing we used to do in design work was to create a composite op-amp i,e strap Jfets to a 5534. This will create dammned good slew rate of 20V/uS upwards with unity gain stability. A reason that the 5534 (low noise version suffix A) is so often used is that it is designed for 600ohm loads. There are IC's around with this configuration, but you will have to sift through the catalogues.
Pays to visit www.vishay.com/company/brands/siliconix/ for more physics understanding. (analogue small signal box)
The bonus of the 5534 as a building block is the high current bipolar o/p with an o/p resistance of 0.3 ohms and can operate from +/- 15 V supply.
The application note you need to get hold of is AN81-3 which goes back to the Siliconix design catalogue dated July 1983. I couldnt' find this although I have the book.
The 5532 is two internally compensated 5534 chips, fitted in the same die. The 5532 is then technically close to max dissipation from a +/- 15V supply if loading 2x 600 ohm outputs. pin 5 & 8 has a compens cap of about 47pF, a figure which I find a bit high.
As you probably know the THD from these blocks is virtually nothing, we are down into noise typ 0.001%.
The TL071/2 family suffers the disadvantage of not being able to slam drive into 600 ohm outputs, and somwhat noisier. I don't use these for audio work.
I am not up to comparing manufacturers similiar devices, like for like, the sonic differences are interesting especially when everyone shuns class B operation, and these IC's use it!
Unfortunately all this technical progress makes the conventional performance and bandwidth of the signal triode tube look rather silly. I do like using tubes but I am more driven to pentodes as they are more efficient and one can do alot more with them. It is a disadvantge in audio designs that I am always fighting to get the noise level to respectable low level. The question of 2nd 3rd 5th harmonics is interesting as this is far more easier to observe in tubes than IC's. Naturally we are up all getting mixed and cancelled in in the output transformer-. on when did it all matter at board level ??? More and more studio performers utilise 2nd harmonic in the mixing process especially in the bass end.
More anon
):rich |
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| TimA |
I have listened to the NE5534 in three different circuits, one where it was configured as a buffer, another where it performs I/V conversion (with no buffer following it), and another where it was used as a balanced to unbalanced converter. In the second two circuits mentioned above I have also listened to many BB fet input, AD bipolar input and AD fet input devices, I have also built a discrete op-amp where the input can be either fet or bipolar. My own preference so far has been for the bipolar devices every time; NE5534, AD797 and the discrete circuit. I find them clearly superior in... their ability to set a natural perspective that has a realistic portrayal of depth, their 'focus' and tonal/textural accuracy, their bass quality. To put thinds into perspective a little more, I have not heard a fet op-amp that didn't sound artificial, cold, sterile and fatiguing to some degree, the OPA627 and AD8610 are partial exceptions here, though I still prefer the sound of the NE5534 for its sheer naturalness!. In my experience the NE5534 is unmatched in its ability to portray the acoustic signature of the recording venue, the AD797 is also a favourite of mine due to its refined sound. I find that a CCS on the output for class A operation improves 'smoothness' and 'purity', particularly in the treble.
Tim. |
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| PMA |
| JFETs have wider linear range of input voltages compared to BJTs. Input linear voltage range of Gm characteristics is about +/-800 mV for JFETs compared to some +/-200mV for BJTs (I speak about input differential pair stage). BJT pair has more steeply sloped Gm curve and more narrow input dynamic range. |
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| richwalters |
I put it to a vote. The 5534 is the best op amp to build audio circuits around. As to circuit details, for optimum low noise performance it pays to keep the o/p feedback resistor back to inverted input less than 10K in this mode of operation. 5K is actually optimum.
The LM1875 power amp is also a good specimen for a general purpose headphone amp.
rich:) |
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| macka |
Somewhere I have an old article from Audio Ameteur my a studio engineer about this topic. I will try and locate and scan for you.
The gist of it was how the 5532/34 is set up in terms if feeback and input filtering regards open/closed loop gain HF Margin. Also input filtering, this is why the 5532 earned such a bad reputation in the CD player with the audio press, so called designers were basically clipping the chip in the HF area.
John Stammer also wrote an excellent article on the application od audio opamps for pro mixer console in AE.
He Chose to add class A biasing and also servos to eliminate outptu capacitors. In comparisons he reckoned the Jenson discrete opamp and and the Borbely were the best sonically.
Not to mention regulators the 3 pins 7815, no way baby, use the Jung hi performance regulators in these applications.
In my own experience I thought these opamps were bearable untill I built the BOSOZ
Ian |
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| Richard C |
For the most natural musical presentation I've found simple SE bipolar designs to work extremely well and are certainly superior to op-amps in this respect.
I wouldn't use an op-amp in an audio amplifier it just isn't necessary: why use 50+ transistors when 5 will do? The sonic performance of a simple discrete circuit can be astounding compared to an equivalent op-amp design.
Who cares whether an amp produces 0.1% THD or 0.001% there are more important factors. |
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| jewilson |
I can't believe some of you folks still believe that a 5532 or a 5534 are good sounding parts. These parts were designed in the early 80's at at the time they still were not as good as PMI OP15 0r 17 and many AD parts.
If you can't tell the difference between these parts and the current crop of Burr Brown or Analog device part you should check with your Doctor Soon.
Questions to Discuss with Your Doctor:
Is your hearing loss on one side or both?
For how long have you noticed the problem?
Has your hearing loss been getting worse over time?
Do you have difficulty understanding other people when they speak?
Do you say "what?" a lot?
When you turn on the television, do others say that it is too loud?
Have you had any kind of ear surgery?
Have you flown in an airplane recently?
Do other people in your family have trouble hearing?
Do you hear ringing in your ears?
Do you suffer from dizziness or loss of coordination?
Have you had been listening to 5534 or 5532.?
Do you currently have an upper respiratory infection?
Have you had any head injuries or strokes in the past?
Are you taking any drugs?
Are speakers from the 1960? |
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| Steve Eddy |
| quote: | Originally posted by jewilson
I can't believe some of you folks still believe that a 5532 or a 5534 are good sounding parts. These parts were designed in the early 80's at at the time they still were not as good as PMI OP15 0r 17 and many AD parts.
If you can't tell the difference between these parts and the current crop of Burr Brown or Analog device part you should check with your Doctor Soon.
Questions to Discuss with Your Doctor:
Is your hearing loss on one side or both?
For how long have you noticed the problem?
Has your hearing loss been getting worse over time?
Do you have difficulty understanding other people when they speak?
Do you say "what?" a lot?
When you turn on the television, do others say that it is too loud?
Have you had any kind of ear surgery?
Have you flown in an airplane recently?
Do other people in your family have trouble hearing?
Do you hear ringing in your ears?
Do you suffer from dizziness or loss of coordination?
Have you had been listening to 5534 or 5532.?
Do you currently have an upper respiratory infection?
Have you had any head injuries or strokes in the past?
Are you taking any drugs?
Are speakers from the 1960? |
Jeeezuz. What would you recommend for someone who still believes that vacuum tubes designed in the early '30s are good sounding parts? Sterilization so they can't reproduce?
se |
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| richwalters |
post 11# Unconvincing diagnosis...... Alot of todays classical/pop music still goes through older consoles which still use 5534's before AD processing, then what happens to it is anyone business. Okay the older Ic's are on their way out, but I always remind people just to take a look at the quality of the electronics and HF that comes out of their CD player. Not all anti-aliasing filters are clean.
In 1985/6 I fitted the OP17 (in lieu of 5534's) in studio consoles located Air Studios in Monserrat (Bahamas), and nobody liked the sound. The same in Hook End studio's, Bagshot (UK). So what's next ?
Super technology is NOT always the answer.
rich |
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| Samuel Jayaraj |
If you have a circuit using the NE5534, just plug in a TLE2141 and check the difference in the perceived naturalness of the sound (remove the compensation cap, if the NE5534 is used in unity gain mode).
Discretre circuitry when executed correctly, outperfom almost all chip opamps, with fewer parts count.
Some here who have preferred the NE5534 and NE5532s need to check these out in wide variety of circuit designs, substituting other opamps as well as discrete circuitry and before long you will use these old champs of the audio industry only when you must. |
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| macka |
A while back Ben Duncan did some tests and comparisons on a wide variety of chips regards distortion spectrographs the 5532 was one of the better ones.
It depends on what you are trying to do and the application of the device. Drop in comparisons a not really apples for apples really.
The better designers select the chip for specific characteristics and use a modest amount of gain per device, class A biasing if required and careful use of FB to avoid overload.
Unfortunately chips almost always have very high open loop gain and low drive capability and are not class a for more than a fraction of a milliamp.
Many are class B and use puesudo distortion cancelling mechanisms leaving the sound subjectively cleansed and acid.
No wonder so called discrete opamps are leagues ahead with direct control of parts count and topology.
macka:) |
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| millwood |
| quote: | Originally posted by jewilson
These parts were designed in the early 80's at at the time they still were not as good as PMI OP15 0r 17 and many AD parts. |
along the same line, let's throw out Newton's laws. afterall, it was discovered a millenium ago. Relativity isn't much better too.
Just because something is old doesn't mean it is bad. |
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| macka |
In an archive thread there were people raving about the Kaneda preamp, a legend never to be repeated.
Well is an identical circuit by Marshall Leach, a discrete universal opamp using dual diff amps both fets and Bi polar.
Ian |
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| jewilson |
SE, as you no there no compairson between a good tube design and old opamps designs.
SE, Sorry to here that you support using the 5532 or 5534. |
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| Steve Eddy |
| quote: | Originally posted by jewilson
SE, Sorry to here that you support using the 5532 or 5534. |
What I support is people using whatever sounds best TO THEM. What I don't support is the intolerance of those who impugn and ridicule others whose tastes and preferences may be different from their own.
Sorry to hear that you're so insecure and troubled by others not liking the same things that you like that you would go to such lengths to ridicule them.
se |
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| mlloyd1 |
This is circuit configured as a gain block makes a fine gain stage. I've used it both as an RIAA stage and line driver. Nice ! :)
| quote: | Originally posted by macka
In an archive thread there were people raving about the Kaneda preamp, a legend never to be repeated.
Well is an identical circuit by Marshall Leach, a discrete universal opamp using dual diff amps both fets and Bi polar.
Ian |
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| PMA |
| I have to support jewilson ;) . NE5532 measures well, but fails when influenced by D/A spikes from CD and RF interference, cannot manage it. He is right, every BB like 2134 etc. is better. And - 5532 has horribly high input bias current and current noise. So called advantage of low voltage noise can be utilized only for source output impedances and input resistors of some 100 Ohms. |
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| Jocko Homo |
Some of the stuff in this thread is ludicrous. But what do I know........30+ years of doing this has taught me nothing.
Jocko |
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| Richard C |
Nope, I've just checked and the original question wasn't "is the NE5532/4 any good?".
Op-amps make sense in low cost and pro equipment where there are constraints on cost, power consumption, board space, heat dissipation and where an impressive on-paper specification is important. But for us DIYers, at least as far as pre-amps are concerned none of the above is really an issue.
Connecting up an op-amp can hardly be described as 'designing a high-end pre-amp'.:rolleyes: |
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| peranders |
| quote: | Originally posted by Asbjorn
Actually I believe jfets sounds alot more like triodes than bipolar too! But this smooth, soft and nice sound it delivers - is it correct or some kind of "coloration" that's being added to the original signal? I'm afraid it is!
But what do you think about jfets and bipolars? Especially sonic experiences have my attention.
:) |
Asbjørn, I think that you have to deside what you want to do and then go for it. JFET's, tubes, BJT's are all very good in good designs AND very bad in bad designs.
Maybe you can take some advice from Jocko if he want to give any. He knows something I believe. |
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| peranders |
| quote: | Originally posted by Asbjorn
Btw, I think ne5532 is better than those popular fet opamps from AD and BB. I think all the AD and BB opamps I've heard sounds bright and undynamic comparede to ne5532. |
Really, you have heard OPA627 and AD8610 in their optimal environments? They are not bad, that's for sure.
My AD8610/BUF634 headphone amp is not boring. :no:
Can be seen here |
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| jewilson |
OP27, OP37, OPA2604, OP249, OP275, LM6172/ AD825/26, AD797 AD8610, OPA627, OPA637, OP134, AD8610, AD8620. These are just a few of the part that sound better than the yesterday news 5532/4 parts.
An for most applications the FET sound better low odd harmonics.
I mean you don't see any bipolars on the front end of any of Nelson's, Curl work now why is that. |
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| TimA |
I am reminded of the story of the ''audiophile'' who returned home from a concert complaining that there was not enough ''presence''. The quest for clarity, detail and precision is fine up to a point, but every recording represents an imperfect replica of a real musical event and posesses imperfections that easily distract the listener from the music. As a musician I know how music sounds both on and off stage, the most cohesive sound is often to be found some way from the stage.
In my view FETs produce an unnatural spotlight on detail, rather like sitting in the front row. I find Bipolar devices convey a more balanced sound, not quite as detailed as the FET sound, though more realistic overall. In general I have found BJTs convey a more realistic sense of perspective. This brings us back to the NE5534 which incidentally is a dual version of the NE5533 according to the datasheet, not the NE5532. I don't pretend it is perfect, my discrete S.E. class A op-amp circuit sounds better to me, but the NE5534, especially when biased into class A, plays music with sufficient clarity, tonal neutrality and a believable perspective in a way that I have not experienced with many more modern IC op-amps.
Regarding the previously suggested (in this thread) visit to the doctor for a cure for the NE5534 ''thing'', doctors are very well educated people who enjoy good music and culture, the NE5534 might be to their liking!
Tim. |
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| peranders |
| quote: | Originally posted by jewilson
I mean you don't see any bipolars on the front end of any of Nelson's, Curl work now why is that. |
This means only that they like them/prefer them in some way. |
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| jewilson |
Well If there were only 709's, 741, uA739, 540's, available in this world then I might think that a 5534 was some kind of marvel. Having said that, na I would use tubes.
Tim, sorry you can here the difference, but where did you do this research. You must have been in bad environment maybe faulty towers. |
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| Jocko Homo |
You forgot TL0x1s,and the like. And LM833s too, although some here seem to think that they are also good.
If they are so good, then why didn't the place that buys my pull-outs want them??
Answer: they couldn't sell them. About the only truly useless **** that I have pulled out in the last 20 years.
Jocko |
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| rickpt |
Some of you (myself included) like so much the NE5534 because it's lowest distortion opamp ever made, it even beats the AD797 in a null test. take the OPA627, it has 20dB more distortion at 20khz than the NE5534 or the AD797(these NE haters guys don’t like the Ad797 too, can you see why?)
if you do the null test to the OPA627 you can clearly see where the frequency compensation(1khz aprox.) point is and there is where distortion rises skyward! and there were the NE really shines, it has a brilliant compensation scheme that maintains the open loop gain linear over the audio band, and the distortion down as well.
And by the way, add more 10db of distortion to the OPA627 if you are driving a 1k load...region were the Ne5534 and the AD797 really shines because distortion is almost the same with load or without
you guys can say all you want but the NE5534 is an audio engineering masterpiece and its performance isn’t equaled by any monolithic device ever made and some of us now this!...
(I can show the various null results of various audio opamps if you guys want)
Best regards
Ricardo |
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| Elso Kwak |
| quote: | Originally posted by rickpt
(I can show the various null results of various audio opamps if you guys want)
Best regards
Ricardo |
Yeah, Ricardo,
Show us your null results. I am looking forward to it!
Ciao,
:) |
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| rickpt |
to the end of this week you will have them, i have to convert all the voltage values to dB and that takes time...
The forum members that dont now this type of mesurement, search the forum and also search the hafler XL280 excelinear manual. there is very relevant info on the null test in this forum...
A test invented by a genius named David Hafler.
the opamps measured were the:
NE5534(texas)
NE5534(signetics)
OPA627BP
AD797
OPA604AP
OP27GP(PMI)
OPA134PA
TL071
Best Regards |
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| john curl |
I second Elso's input. In principle, the AD797 should run rings around the 5534. Please understand, I have used the 5534, since 1977, when I was first sampled by Signetics. It was a serious improvement in audio IC op amp design and performance. However, we found that IF you bypassed the input stage and substituted a fet input stage, we could make a better sounding device. We (my tech actually) made them for Dave Wilson for his $100,000 speaker system's active equilizer. Dave paid $80 each, 15 years ago, I believe.
The AD797 is similar to the 5534, but significantly improved, at least in principle. I'm sure that the designer of the AD797, Scott Wurcer, knows the ins-and-outs of the 5534. He would not have made an inferior device on purpose, at least. |
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| PRR |
> The AD797 is similar to the 5534
The spec-sheet puffery says otherwise:
"The new architecture of the AD797 was developed to overcome inherent limitations in previous amplifier designs. Previous precision amplifiers used three stages ..... The AD797 on the other hand, uses a single ultrahigh gain stage to achieve dc as well as dynamic precision."
The way they draw it, I was very puzzled for a while. Mostly it is a semi-conventional bipolar op-amp, though it takes great advantage of the "Complementary Bipolar (CB) process" (good PNP and NPN on the same die) which was not available to the 5534 designer. But the bootstrapped current mirror and the compensation it allows are pretty wacky, at least novel, to these old eyes.
On gross-specs, it has noise voltage similar to or better than 5534. Input current, rather high on 5534, has been reduced on the 797, but still can't be confused with a TL071. Output current is almost/not-quite as high as 5534. Gain at low-Z loads is better. Max rated supply voltage does not match the 5534's exceptional +/-22V, which may not matter to most people but is sometimes handy. (I'm not sure there is a difference in the silicon, or just in the specs. Certainly normal +/-18V chips do not explode at 18.1 or even 20 volts.)
Others have noted the 5534's unhappiness when you feed it DAC spikes. My reaction is: "Don't DO that if it hurts!" The 5534 was designed for an older mellower world without digital gizmos, and we always put some thought into out-of-band ****-control before signals hit an active junction. Yes, for typical ****-levels, a bipolar is wiped-out and most FETs just take it without distress. And not dealing with ****-control may lead to better sound. But that is one of the trade-offs we face. |
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| rickpt |
the null test results;)
cheers
Ricardo |
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| Jocko Homo |
Might be a radically new concept to some.
Mandatory to the rest of us. Even with JFETs, although they tolerate it more easily.
Jocko |
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| Jocko Homo |
A friend recently tried to sell one of his D/A converters (built by me) that he has an extra one of.......
Tried to sell it to a guy who just spent $$$$$ on having all of his system cryogenically treated. (I have no idea why....waste of money that he could have spent on me!)
Anyway, he declined to buy the D/A box. Said that he now heard "too much detail", and that "frightened" him.
No explanation why some people like to spend $$$ on stuff, yet want it to sound all mucked up.
IOW, if JFETs have "too much detail", maybe something else is wrong with your system.
Uh, change that "maybe" to "probably".
Jocko |
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| dimitri |
The art of electronic engineering is to put the right component in a right place within a budget, not to populate your board with the most expensive, most recent so-called "technological achievements". Don’t choke the cat with cream! :D
… and you can find helpful Scott Wurcer design note AN348 here:
http://www.analog.com/UploadedFiles...001060AN348.pdf
and ad797 story here:
"An Operational Amplifier Architecture with a Single Gain Stage and Distortion Cancellation," AES Preprint 3231 |
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| johnferrier |
| quote: | Originally posted by dimitri
and ad797 story here:
"An Operational Amplifier Architecture with a Single Gain Stage and Distortion Cancellation," AES Preprint 3231 |
Hi Dimitri,
Do you have an online source for the ad797 story? Google didn't help me.
JF |
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| jewilson |
Ricardo,
What do these numbers mean? What type of test did you run, what was the point of the test and what does it prove. In addition, let us in on you test configurations so we can be enlighten.
:confused: |
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| millwood |
| quote: | Originally posted by jewilson
Well If there were only 709's, 741, uA739, 540's, available in this world then I might think that a 5534 was some kind of marvel. Having said that, na I would use tubes. |
I used to use 324s and thought they were great, until I used the TL0xxs. Well, the 324s aren't bad with a light load. But under heavy load (I were bootstraping them in a power amp), they didn't do too well.
| quote: | Originally posted by jewilson
Tim, sorry you can here the difference, but where did you do this research. You must have been in bad environment maybe faulty towers. |
it must have been the power cords, :) |
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| johnferrier |
| quote: | Originally posted by dimitri
I can send it to you not earlier than a New Year. |
The other sources you provided are fine. Thanks!
JF |
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| peranders |
| quote: | Originally posted by rickpt
the null test results;)
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What is the file type? I don't get any .??? at the end. |
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| TimA |
Ricardo,
Thankyou for the op-amp null test figures....interesting!
Tim. |
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| rickpt |
setup: non-inverting amplifier with a(I chose this gains figure to use the OPA637 and the resistors were handy at that time) gain of five times and a 50k pot at the front end.a typical single opamp Pre-Amplifier;)
distortion could be a little lower if I used lower gain settings... as the setup was equal to all opamps,this cannot be blamed:nod:
about the null test like I said before, there is a lot of input about this test made by my friend Tube Dude in this forum, just search...
in short terms, it's a differential test that directly compares the input with the output leaving only the thing that cant be nulled, all nonlinearities created by the amplifying stage! lower the value, more the output resembles the input! one thing great about the test is that the distortion of the generator isn’t a problem like the typical distortion tests and that severely limits resolution of those tests
about the file, it's a word file
cheers
Ricardo |
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| sonnya |
??
First of all.. It can be blamed.
Design you circuit to match the opamps you are using.
1. A good example is the OP275GS/GP from analog. On page 9 in the datasheet there is a section called "Attention to source impedance Minimizes distortion"
There is descriped how a source impedance of more than 2Kohm and unballanced will affect its distortion performance alot.
That is because of capacitance modulation.
2. The AD797 outperforms the NE5534. There was an article in EW about capacitance distortion. The author have made a very pure sine wave oscillator. The distortion dropped below the NE5534 when he added a series resistor of 100R to the Cf. Reason .. Because of the very low rbb of the input diff. pair it needed a series resistor to dampen the capacitive interactions.
Look at page 10 in the datasheet.
So when it all sums up. The tests have to take there working conditions into account before comparing the specs and sound quality.
Sonny :smash: |
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| rickpt |
| quote: | | Design you circuit to match the opamps you are using. |
whit a 50k pot that gives you about 10k of output inpedance at mid point position, fet amplifiers should be at home, and bipolar amplifiers should perform much worse... that wasn’t the case!
| quote: | | 2. The AD797 outperforms the NE5534. There was an article in EW about capacitance distortion. The author have made a very pure sine wave oscillator. The distortion dropped below the NE5534 when he added a series resistor of 100R to the Cf. Reason .. Because of the very low rbb of the input diff. pair it needed a series resistor to dampen the capacitive interactions. |
did you verify this with a null test? remember that the null test isn’t a typical thd test! all non linearity’s are measured.
about that resistor I don’t believe that was the case... I believe that Mr. Bateman had a parasitic oscillation when he inserted the AD797 on the circuit, and that resistor dampened that oscillation, and off course, distortion was lower, so nothing more than a base stopper...
now look at the typical diy'er, normally the topology is the same and only opamps are swapped...that was what I did but instead of listening, I was measuring;)
it's fairly easy to do a null test , so do it yourself and find your results...
cheers
Ricardo |
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| johnferrier |
| quote: | Originally posted by peranders
What is the file type? I don't get any .??? at the end. |
It's a zip file with a MS-Word doc inside. I just redownloaded, it works fine here.
JF |
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| JoeBob |
| I like the NE5532, shoot me I don't care. I find it to be the best sounding small-signal opamp I've tried, and I've fiddled with many others. Maybe I didn't implement the others correctly enough, or maybe it's just easier to achieve good sound with the NE5532/NE5534 than others. Either way, to each his own... |
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| jewilson |
Still you still have not answered the question. What types of test are you running? Can’t you be just a little more specific regarding you claims?
Offset , THD , Gain, BW, Phase, Slew Rate, Transient , Noise
What is your null? |
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| dimitri |
| I beleive, that that null test was published in WW in 80th |
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| jewilson |
| This is not a standard recognized test in the audio industry. It is not like a true measurement of performance like distortion or a spectral analysis or noise. So this is your argument :clown: |
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| rickpt |
so explain me and other forum members why this isnt a valid or true way of measuring performance of an amplifier?
cheers |
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| PRR |
> What is the file type?
MS-DOC inside a ZIP. But it is just 1K of text:
the null test results - cheers - Ricardo
[Opamp _ _ _ _ _ _ _ 100hz _ _1khz _ 10khz _ _20khz _40khz
NE5534(signetics) _ 2,6mv _ 3,0mv _ 3,4mv _ _4,4mv _ 6,4mv
NE5534(TI) _ _ _ _ _ _2mv _ _ 2mv _ 3,2mv _ _4,6mv _ _ 7mv
AD797 _ _ _ _ _ _ _ 4,6mv _ 4,6mv _ 4,6mv _ _6,4mv _ _ 7mv
OPA627BP _ _ _ _ _ _2,4mv _ 3,3mv _10.8mv _ 20.2mv _ _40mv
OPA604AP _ _ _ _ _ _2,8mv _ 5,6mv _ _12mv _ 20.2mv _ _40mv
OP27GP _ _ _ _ _ _ _2,2mv _ _ 5mv _ _20mv _ _ 40mv _ _75mv
TLO71 _ _ _ _ _ _ _ _10mv _12,6mv _ _40mv _ _ 80mv _ 156mv
OPA134PA _ _ _ _ _ _ _3mv _ 4,2mv _16,6mv _ 33,6mv _ _67mv
Whit 1k load:
NE5534(signetics) _ 2,8mv _ _ 3mv _ 4,2mv _ _5,4mv _ 9,0mv
AD797 _ _ _ _ _ _ _ 4,6mv _ 4,6mv _ 5,2mv _ _6,4mv _10,6mv
OPA627 _ _ _ _ _ _ _5,6mv _ 5,6mv _15,2mv _ 25,8mv _41,6mv
OPA604 _ _ _ _ _ _ _6,4mv _ 6,4mv _17,6mv _ 25,8mv _41,6mv
OPA134 _ _ _ _ _ _ _6,2mv _ 6,4mv _17,6mv _ 35,2mv _70,4mv
To convert mv to dB: dB= 20log (v\vref)
This test was made with a 2volt peak to peak input voltage(vref)
> the null test isn’t a typical thd test! all non linearity’s are measured.
> This is not a standard recognized test in the audio industry.
No; and perhaps because it is one of the most embarassing things you can do to an amplifier. It can also be called a "Total Garbage" test: everything wrong stands out. The numbers are probably not important except for the most general classification. But it is a widely-used design-bench test, because it is easy and a look at the O'scope display tells the savvy designer if he/she has phase shift, noise, low-order distortion, or a lot of high-order crapola, and if it happens on peaks or at zero-cross or some intermediate point (marginal instability). I've seen null-tests published in reviews, though I think you need to do a lot of such tests yourself to get a good feel for what it may be able to tell you.
> It is not like a true measurement of performance like distortion or a spectral analysis or noise.
Ah, but what is "TRUTH"? It has been clear for 50 years (actually since pentodes and feedback) that THD-number isn't "truth". Spectra are so messy. And there are so many ways to lie about noise. The total-garbage out of an amp is arguably no worse than most of our other "measurements", many of which have little to do with how we hear.
I thank Ricardo for the numbers, but without knowing how much of the number is phase-shift, noise, low- or high-order distortion, or if the test rig was optimally adjusted for each amp (in ways we could do in the real world), I don't trust it without trying things on the scope. |
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| jewilson |
PRR,
While some of the standard test may not provide the complete picture of an amp performance, many they are still the best tests we have going. Of course, we cannot hang our hat on THD however there is important information in spectrum analysis.
My self, I really like doing impulse testing with a FFT. However as you stated their no test currently available that tell us one circuit sound better than another does. Having said that, we can get a great deal of truth about the performance of components with these conventional tests. |
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| Asbjorn |
| quote: | Originally posted by jewilson
I can't believe some of you folks still believe that a 5532 or a 5534 are good sounding parts. These parts were designed in the early 80's at at the time they still were not as good as PMI OP15 0r 17 and many AD parts.
If you can't tell the difference between these parts and the current crop of Burr Brown or Analog device part you should check with your Doctor Soon. |
It isn't hard to tell the difference. But have you ever listened to these BB and AD parts? How do you think they sound vs ne5532?
| quote: | Originally posted by Samuel Jayaraj
Discretre circuitry when executed correctly, outperfom almost all chip opamps, with fewer parts count. |
Agree!
| quote: | Originally posted by jewilson
OP27, OP37, OPA2604, OP249, OP275, LM6172/ AD825/26, AD797 AD8610, OPA627, OPA637, OP134, AD8610, AD8620. These are just a few of the part that sound better than the yesterday news 5532/4 parts.
An for most applications the FET sound better low odd harmonics.
I mean you don't see any bipolars on the front end of any of Nelson's, Curl work now why is that. |
That's simply not true. Please explain what such as the op275 does better than ne5532 in a listening test! :confused:
| quote: | Originally posted by TimA
I am reminded of the story of the ''audiophile'' who returned home from a concert complaining that there was not enough ''presence''. The quest for clarity, detail and precision is fine up to a point, but every recording represents an imperfect replica of a real musical event and posesses imperfections that easily distract the listener from the music. As a musician I know how music sounds both on and off stage, the most cohesive sound is often to be found some way from the stage.
In my view FETs produce an unnatural spotlight on detail, rather like sitting in the front row. I find Bipolar devices convey a more balanced sound, not quite as detailed as the FET sound, though more realistic overall. In general I have found BJTs convey a more realistic sense of perspective. This brings us back to the NE5534 which incidentally is a dual version of the NE5533 according to the datasheet, not the NE5532. I don't pretend it is perfect, my discrete S.E. class A op-amp circuit sounds better to me, but the NE5534, especially when biased into class A, plays music with sufficient clarity, tonal neutrality and a believable perspective in a way that I have not experienced with many more modern IC op-amps.
Regarding the previously suggested (in this thread) visit to the doctor for a cure for the NE5534 ''thing'', doctors are very well educated people who enjoy good music and culture, the NE5534 might be to their liking!
Tim. |
WOW! I totally agree! ;)
The FET sound really has an unnatural spotlight somewhere, and yes, it does at first sound more detailed... But try listening to a good classical recording, and you will find that the bipolar actually is more "shaded"/detailed, it just don't advertise it! I think the spotlight produced by fets tend to cover things outside the spot. Try using good recordings of real instruments next time, and tell me what happened!
| quote: | Originally posted by rickpt
the null test results;)
cheers
Ricardo |
Thanks! Very interesting! :)
Mvh Asbjørn |
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| mlloyd1 |
Having played with the null test a bit when I first saw the Hafler XL280 amp manual, I HAVE to agree with what PRR said. My opinion is null testing is useless if you're not going to look at the residuals on a good scope and interpret what you see correctly.
Hmmmm, that could probably be said for THD meters also, now that I see the words.
However, I'll agree it is fun to place around with :) As usual in this hobby/business, the real benefit comes from understanding the results.
| quote: | Originally posted by PRR
.... a look at the O'scope display tells the savvy designer if he/she has .... crapola, ....
....
I don't trust it without trying things on the scope. |
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| sonnya |
| quote: | Originally posted by rickpt
whit a 50k pot that gives you about 10k of output inpedance at mid point position, fet amplifiers should be at home, and bipolar amplifiers should perform much worse... that wasn’t the case!
did you verify this with a null test? remember that the null test isn’t a typical thd test! all non linearity’s are measured.
about that resistor I don’t believe that was the case... I believe that Mr. Bateman had a parasitic oscillation when he inserted the AD797 on the circuit, and that resistor dampened that oscillation, and off course, distortion was lower, so nothing more than a base stopper...
now look at the typical diy'er, normally the topology is the same and only opamps are swapped...that was what I did but instead of listening, I was measuring;)
it's fairly easy to do a null test , so do it yourself and find your results...
cheers
Ricardo |
No i have not verified the test setup.
Not for being a pain. Still before you can compare the opamps, there optimum working conditions, as described by the designer have to be meet.
It could be bypassing caps, as already mentioned source impedance. (Jfet are subjected to higher distortion when the imbalance of the source impedance is not corrected). Notes on how to add a series resistor to the Cf like the one in the AD797 datasheet ... The addition of RS has actually great impact on the open-loop gain and phase margin as shown in the datasheet figure 14.
Then you have to have very high CMRR on your measurement tools, not to get the result distorted by a low CMRR.
When all this is okay, then you can start comparing.
Even though you still needs to take PRR's words into account.
| quote: | Originally posted by PRR
> What is the file type?
I thank Ricardo for the numbers, but without knowing how much of the number is phase-shift, noise, low- or high-order distortion, or if the test rig was optimally adjusted for each amp (in ways we could do in the real world), I don't trust it without trying things on the scope. |
Regards
The pain. |
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| rickpt |
| quote: | | I thank Ricardo for the numbers, but without knowing how much of the number is phase-shift, noise, low- or high-order distortion, or if the test rig was optimally adjusted for each amp (in ways we could do in the real world), I don't trust it without trying things on the scope |
PRR, these measurements where made with a scope, I saw the residual wave! at lower frequencies it was dominated by noise on all opamps! at higher frequencies it was clear that the residual was dominated by harmonic disrtortion+noise, specially the fet devices and the op27!all opamps have good bandwidth and I didn’t use any input filtering, so phase wasn’t a problem!
that thing about optimizing topology sounds very nice on theory, but how can you be sure you are comparing the opamps only or you are comparing different topologies? where to set the line?
this test wasn’t made to measure the lower distortion I could achieve but compare different devices on a typical application! A Pre-Amplifier
| quote: | | Jfet are subjected to higher distortion when the imbalance of the source impedance is not corrected |
how can you balance inpedance on both inputs of a opamp when you have a potentiometer on one input? it's just show another type of distortion that affects fet devices, common mode distortion!
instead saying my test is wrong, please do the test yourself and refute my findings! it would create a very nice discuss
Cheers |
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| Terry Demol |
| quote: | Originally posted by Jocko Homo
Some of the stuff in this thread is ludicrous. But what do I know........30+ years of doing this has taught me nothing.
Jocko |
You crack me up sometimes Jocko!
I'm not even buying into this thread.... it's an entertaining read
though :D
Terry |
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| Jocko Homo |
Most be losing my touch. Didn't think that I was getting that soft in my old age.
Oh well..........
Jocko |
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| johnferrier |
| quote: | Originally posted by rickpt
how can you balance inpedance on both inputs of a opamp when you have a potentiometer on one input? it's just show another type of distortion that affects fet devices, common mode distortion!
|
One could approximate the typical volume control setting. Also, Borbely has described how cascoding the FET input fixes the problem with input capacitance.
See section titled "Cascode to the Rescue" on page 30 here:
http://www.tkhifi.com/div/Erno_Borb...t_articel_1.pdf
Borbely uses discrete circuitry; however, it seems that cascoding ought to help integrated devices as well.
JF |
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| Terry Demol |
| quote: | Originally posted by johnferrier
One could approximate the typical volume control setting. Also, Borbely has described how cascoding the FET input fixes the problem with input capacitance.
See section titled "Cascode to the Rescue" on page 30 here:
http://www.tkhifi.com/div/Erno_Borb...t_articel_1.pdf
Borbely uses discrete circuitry; however, it seems that cascoding ought to help integrated devices as well.
JF |
OPA627 does have a form of cascoding on IP stage.
Cheers,
Terry |
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| Terry Demol |
| quote: | Originally posted by rickpt
PRR, these measurements where made with a scope, I saw the residual wave! at lower frequencies it was dominated by noise on all opamps! at higher frequencies it was clear that the residual was dominated by harmonic disrtortion+noise, specially the fet devices and the op27!all opamps have good bandwidth and I didn’t use any input filtering, so phase wasn’t a problem!
|
For a given load, quiescent current and with both devices
degenerated for same gain, Jfets are more linear than BJT's
but not by much. I've measured it with AP.
However the jfets have much worse capacitance modulation with
voltage swing so I assume this is hard to deal with in monolythic
low supply voltage (+-15) implementations and at higher
frequencies there is less feedback to correct it.
Having said this, I feel a good newer opamp such as OPA627
is quite superior sonically than the 5534 in most low gain
applications.
I (and client) have compared 5534 vs 627 in mixing desk summing
point and the 5534 became much more sonically constricted
when more channels+level were introduced. The 627 was
cleaner and stayed cleaner longer with bigger
levels and more channels. No question.
We have compared 5534 vs 627 in DAC I-V, as stated before
the 5534 is a bit slow for this application, the 627 was way better.
| quote: |
instead saying my test is wrong, please do the test yourself and refute my findings! it would create a very nice discuss
Cheers [/B] |
I'll have a play with it, looks interesting.
As a related point you appear to be a pro audio guy,
I know early series SSL's were riddled with 5534's and
these consoles are known for thier bad sound (but incredible
flexibility) They have since introduced the J series which was
much better and now the K series. Are these still full of 5534's?
Terry |
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| rickpt |
| quote: | However the jfets have much worse capacitance modulation with
voltage swing so I assume this is hard to deal with in monolythic
low supply voltage (+-15) implementations and at higher
frequencies there is less feedback to correct it. |
This can be partially dealt with a cascode...
| quote: | I (and client) have compared 5534 vs 627 in mixing desk summing
point and the 5534 became much more sonically constricted
when more channels+level were introduced. The 627 was
cleaner and stayed cleaner longer with bigger
levels and more channels. No question.
We have compared 5534 vs 627 in DAC I-V, as stated before
the 5534 is a bit slow for this application, the 627 was way better.
|
for me those are just a subjective comments and doesn’t mean a thing, some like apples, others like oranges...
Remembers me one talk I had with a friend that is the Meyer Sound loudspeakers importer for Portugal, they had one model that had one type of compression driver that generated a lot of distortion because of the used topology of the horn, but people seamed to like very much that speaker wen they first listened to it, because of it's rich highs;)
As you can see the ear can be easily tricked...:nod:
| quote: | As a related point you appear to be a pro audio guy,
I know early series SSL's were riddled with 5534's and
these consoles are known for thier bad sound (but incredible
flexibility) They have since introduced the J series which was
much better and now the K series. Are these still full of 5534's? |
There are only 2 SSL consoles that I know of, in Portugal and are both 4000 series, and pretty old by now, so I really cant answer that question but there is the SSL 9000 preamp schematic floating around the web and uses the NE5534 and MAT02...
Here in Portugal we have a pretty small music market and it isn’t easy to rentable such an expensive console.| quote: | I know early series SSL's were riddled with 5534's and
these consoles are known for thier bad sound |
All sound engineer I know say that those mixers sound great, and almost all studios around the world has a SSL4000 console, if its so bad why it is still used?;)
Cheers
Ricardo |
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| JFETglare |
Wow, what a thread... :D
I find the 5532's sound inoffensive and honest, for lack of a better word... It reminds me a bit of a 4556.
Anyway, I always find myself going back to the sound of a BJT over a JFET. If I listen to two circuits, each carefully designed and built to accomodate either transistor, I find the JFET one has something that slowly wears on my nerves. It is an artificial sound, mostly concentrated in the upper presence band.
The BJT sounds more neutral in comparison, and often times seems to sound more open and spacious.
Though not exactly on topic, I find MOSFETS configured as a gain device can often have a sweet sound, almost triode like. They are sensitive to circuit design however... I have listened to some MOSFET amps that sound "misty" and thin. I wish MOSFETs were not so static sensitive, and that they had a better reliability record--they are not forgiving devices, certainly nothing like a BJT. |
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| Terry Demol |
| quote: | Originally posted by rickpt
This can be partially dealt with a cascode...
|
As has the 627 in its front end, amongst other advanced
tricks to reduce thermal feedback induced distortions
common on most opamps.
| quote: |
for me those are just a subjective comments and doesn’t mean a thing, some like apples, others like oranges...
Remembers me one talk I had with a friend that is the Meyer Sound loudspeakers importer for Portugal, they had one model that had one type of compression driver that generated a lot of distortion because of the used topology of the horn, but people seamed to like very much that speaker wen they first listened to it, because of it's rich highs;)
As you can see the ear can be easily tricked...:nod:
|
"Rich" to me means distortion but nice distortion. It has it's
place. It doesn't mean "transparent". I think both can be nice
but are very different.
WRT my comments about 627:
Mark Levinson uses the 627 as I-V in the flagship 30.6 dac, Sonic
Frontiers offered it as the top upgrade for their kit dacs. Most
aftermarket modifiers offer it as an upgrade for typical opamps.
It is widely used in many hi-end products for critical locations.
Maybe you could even do a search on DIY audio and see how
many people have tried it with great success.
I did listening tests which formed my initial opinion. I let others do
the same, they came to same conclusion. I did research on the
net and found most others had the same opinion.
When you have groundswell of like opinion from many sources
that are unbiased that is a good indication that your own
results are close to the mark. I can go on about methods,
equipment, topologies, etc suffice to say my comments are
not based on singular unsupported events. I am careful not
to do this on internet as it adds to misinformation.
Also it is a very expensive device, no one uses it unless
there are real sonic advantages, and this is why it is never
in pro gear.
| quote: |
There are only 2 SSL consoles that I know of, in Portugal and are both 4000 series, and pretty old by now, so I really cant answer that question but there is the SSL 9000 preamp schematic floating around the web and uses the NE5534 and MAT02...
Here in Portugal we have a pretty small music market and it isn’t easy to rentable such an expensive console.
All sound engineer I know say that those mixers sound great, and almost all studios around the world has a SSL4000 console, if its so bad why it is still used?;)
|
Lots of people love the sound of early SSL's especially
when they slam the master buss compressors, it is a rock & roll "sound" , however it is a long way from transparent. The SSL
is king of flexibility, automation, total recall and ease of layout. It
is very powerful.
However most audiophile type engineers prefer the Amek 9098,
API discrete, Neve and other consoles for their more open sound.
This is one of the main reasons SSL introduced the 9000J series
and now the K series, to compete with these products
Lucasfilms Skywalker director of music Leslie Ann Jones sums it
up well in the 4th last paragraph "for us....
http://emusician.com/ar/audio_agony_ecstasy_choosing/
I custom build electronics for direct to stereo recording and NO
console or mixing in process.
So I'm coming from a different level of performance compared
to most engineers that just mic it all up and run the faders up.
But for rock and roll you need the power and flexibilty of a
huge desk with its 100's of opamp stages.
Not for me.
Regards,
Terry |
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| Christer |
| quote: | Originally posted by Terry Demol
Also it is a very expensive device, no one uses it unless
there are real sonic advantages, and this is why it is never
in pro gear.
|
I must clearly be misunderstanding you here Terry??
The only conclusion I can draw from that sentence is that
there is no real sonic advantage to the 627, but that seems
to contradict yourself having spent three previous
paragraphs telling how good it is. Could you please clear
up my confusion. |
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| Terry Demol |
| quote: | Originally posted by Christer
I must clearly be misunderstanding you here Terry??
The only conclusion I can draw from that sentence is that
there is no real sonic advantage to the 627, but that seems
to contradict yourself having spent three previous
paragraphs telling how good it is. Could you please clear
up my confusion. |
To clarify,
Have a look at most pro gear and compare the cost to hi-end
gear. Work out how much that gear is rolling out the factory
door (divide retail by around 4).
The 627, being possibly the most expensive audio opamp
available is finacially unviable in most of this gear.
The exceptions are stuff like cranseong / avalon etc but
these designs are discrete anyway... but that's another
story....
gotta go, tonight I'm actually playing some music (gtr) for a
change, tech hat is officially off.
Cheers,
T |
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| Christer |
| quote: | Originally posted by Terry Demol
To clarify,
Have a look at most pro gear and compare the cost to hi-end
gear. Work out how much that gear is rolling out the factory
door (divide retail by around 4).
The 627, being possibly the most expensive audio opamp
available is finacially unviable in most of this gear.
The exceptions are stuff like cranseong / avalon etc but
these designs are discrete anyway... but that's another
story....
gotta go, tonight I'm actually playing some music (gtr) for a
change, tech hat is officially off.
Cheers,
T |
OK, so the problem is that pro-gear is more cost-sensitive
than I thought. Well, thinking of it, for a megachannel mixing
console it would be quite a lot of money, of course. |
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| Geoff |
Terry
You have said:
"We have compared 5534 vs 627 in DAC I-V, as stated before
the 5534 is a bit slow for this application, the 627 was way better."
and:
"Mark Levinson uses the 627 as I-V in the flagship 30.6 dac, Sonic
Frontiers offered it as the top upgrade for their kit dacs. Most
aftermarket modifiers offer it as an upgrade for typical opamps.
It is widely used in many hi-end products for critical locations."
How does this correlate with TI's recommendation for their recent 24bit 192kHz dac chip, the PCM1792? The datasheet for this dac recommends using the NE5534 for I/V conversion. Given the selection of in-house op-amps from which to choose (including the OPA627), they must have a very good reason for this recommendation.
I would have expected a bias towards the more expensive (higher profit margin) devices in their portfolio so the NE5534 would appear to have a significant advantage over the OPA627 in this circuit. TI/BB have recommended the OPA627 for I/V conversion in earlier publications, so there must be an explanation for this seemingly (to some) retrograde step.
It is also interesting to note that TI have recommended a Linear Technology op-amp for the differential circuit, so presumably their selections have been made on performance grounds rather than cost/profit.
Geoff |
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| millwood |
| quote: | Originally posted by Geoff
How does this correlate with TI's recommendation for their recent 24bit 192kHz dac chip, the PCM1792? The datasheet for this dac recommends using the NE5534 for I/V conversion. Given the selection of in-house op-amps from which to choose (including the OPA627), they must have a very good reason for this recommendation.
Geoff |
I am pretty sure that TI/BB knows about their devices, and electronics in general a lot less than ur arm-chair designers here.
:) |
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| Aud_Mot |
To those who do not like the Null Test Method.
As I recall this is the method Bob Carver used in is legeandery Stereophile Amplifier challenge.
For those unfamilar with the story (about 15 years ago) Bob Carver was able to make one of his "un-audiophile quality" solid state amplifiers sound like an audphile's reference tube amp, a Conrad Johnson P-P 65 W/Ch tube amp. He was successfull and the tool used was the Null test mentioned and maligned by some previously.
One channel of the C-J was one amp, the Carver was the other. Bob then tweeked the Carver until there was no sound coming out of the monitor speaker. This method allowed him to duplicate the C-J's transfer function. This made the Carver amp sound (some might say distort) identical to the C-J amp.
Sounds like an example of a uselful testing tool to me.
Aud_Mot |
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| richwalters |
So far the forum has discussed various chip merits, however as I worked with Neve in the mid to late 80's, we always used transformers as the in & out interface, and never raw signals direct to any mixer or line input, even if balanced. Naturally the studio's wanted the best quality and they got it regardless of the quantity of transformers was used.. The R. Neve legend remains electronically superb to the day.
The electronically balanced input configuration was never used in Neve consoles, mixers or ISA discretes. The secret probably lay in those lovely transformers; the subject and technical content of which and the EQ is still copyright protected. So to assess subjective sound off the bench without a similiar setup is prone to so many errors.
rich |
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| Jocko Homo |
As I understand it, the digital audio group is based in Japan, so who knows what those guys listen for.
Maybe it is just their way of saying that TL071s suck.
And as for transformers......
If I was building something with lots of op-amps, that were susceptible to RF and stuff, I would transformers to keep as much of it as possible out. Not a bad idea.
Jocko |
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| richwalters |
Neve's philosophy works......nobody copied it before they found out it was too late.........in the meantime most other manufacturers decided to cut costs and go for electronic inputs.
As for the TL071.........No...... That one isn't in my vine and yet it's everywhere. No harm in Vu Meters that' about it's home place.
rich |
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