rickpt said:
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.
PRR said:
Regards
The pain.
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
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
Re: Good grief, Charlie Brown........
You crack me up sometimes Jocko!
I'm not even buying into this thread.... it's an entertaining read
though 😀
Terry
Jocko Homo said:
You crack me up sometimes Jocko!
I'm not even buying into this thread.... it's an entertaining read
though 😀
Terry
Only sometimes???
Most be losing my touch. Didn't think that I was getting that soft in my old age.
Oh well..........
Jocko
Most be losing my touch. Didn't think that I was getting that soft in my old age.
Oh well..........
Jocko
rickpt said:
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_Borbely_fet_articel_1.pdf
Borbely uses discrete circuitry; however, it seems that cascoding ought to help integrated devices as well.
JF
Douglas Self has a website with THD graphs of the NE5532 and the OPA627 (and other BJT and FET opamps).
See:
http://www.dself.dsl.pipex.com/ampins/webbop/opamp.htm
JF
See:
http://www.dself.dsl.pipex.com/ampins/webbop/opamp.htm
JF
rickpt said:
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.
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
This can be partially dealt with a cascode...
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...
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?😉
Cheers
Ricardo
Wow, what a thread... 😀
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.
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.
rickpt said:
As has the 627 in its front end, amongst other advanced
tricks to reduce thermal feedback induced distortions
common on most opamps.
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...
"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.
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
Terry Demol said:
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.
Christer said:
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
Terry Demol said:
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.
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
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
Geoff said:
I am pretty sure that TI/BB knows about their devices, and electronics in general a lot less than ur arm-chair designers here.
🙂
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
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
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
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
TI may own B-B, but......
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
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
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
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