Well, there was a generic design in the Design of Active Crossovers book, which can be easily modified for most requirements. It does not however use the ultra-low noise technology of the new preamp except in a few places. Is that what you are thinking of?
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Thank you for publishing your new design, Mr Self. Thank you too for the books.
Many of the readers here are in love with exotic parts, hence the quick dismissal of good opamps. They don't realize that even the top hifi manufacturers have opamps like the 5532. I posted recently that the best DAC Stereophile has seen, the Bricasti M1 too has opamps for I/V duties. The slamming came so fast.
Bonsai's arguing with a designer whose latest $4K hi-res DAC can't do a single bit over CD rez.
Many of the readers here are in love with exotic parts, hence the quick dismissal of good opamps. They don't realize that even the top hifi manufacturers have opamps like the 5532. I posted recently that the best DAC Stereophile has seen, the Bricasti M1 too has opamps for I/V duties. The slamming came so fast.
Bonsai's arguing with a designer whose latest $4K hi-res DAC can't do a single bit over CD rez.
I saw your design on that thread - what's the technical justification for using LME49720 for I/V duty?
And that's not a slamming? Oh, the irony
I agree- I think for what you pay they are great Joachim and at 30 years old they keep on shining.
The OPA6x7 is expensive I think because the DC specs for a FET input device are very good, especially the offset and noise. I think this may also be why the output current is limited. JFET'S tend to be more drifty than bipolars and chip heating when driving heavy loads could be a factor. Or is it just an expensive process? Maybe Scott or one of the IC designers could comment?
yep, I was going to mention exactly this earlier but Thorsten seemed too intent on proving their worth in the design. the opa827 especially is a magnificent chip, input voltage noise in particular is much lower, drift only slightly higher, lower noise density, lower current noise etc etc. they obviously aimed to improve on it given the naming and they did so, pity they didnt make an SM grade of it. for bipolars of course there is the lme49990 as well, but thats not really an apples to apples comparison
A question to the designer...
Well I managed to get hold of a copy and I must say it's very interesting comparing this with your earlier "Precision Preamp" of 16 years ago. The new design does seem somewhat quieter in absolute terms and particularly for nominal listening levels.
There are a few questions that I hope Doug might share his thoughts on though.
1. In your earlier design, the "return to flat" feature of the boost and cut curves was a major design point and if I may quote from way back yonder, "Boosting 10Khz is one thing, but boosting 200Khz is quite another and can lead to some interesting stability problems". Other than perhaps additional complexity of design is there a reason why that approach wasn't incorporated here in the 2012 preamp ?
(I believe that some of todays "high end" sources such as SACD can apparently produce large amounts of HF hash outside the audio band, a format that I believe wasn't around back then).
2. The 2012 design while still using bipolar opamps seems to do away with all the AC coupling that was so obvious in the Precision Preamp. In that design it was to eliminate DC currents in the pot wipers and to give silent switching when the "tone defeat" relay was operated, something that appears not to be done here.
Is the DC question in practice a non issue here, given the lower impedances and so on ?
3. Finally, one of those NE5532 questions. Are all widely available examples (thinking manufacturers here) similar in performance ? There's always the usual "web chatter" about for example TI ones being inferior and the old Signetics being the best and so on. Is there any truth lurking there or not ?
You finished back 1996 asking whether that was the quietest preamp ever yet built. Perhaps that statement should be moved to the 2012 design
Well I managed to get hold of a copy and I must say it's very interesting comparing this with your earlier "Precision Preamp" of 16 years ago. The new design does seem somewhat quieter in absolute terms and particularly for nominal listening levels.
There are a few questions that I hope Doug might share his thoughts on though.
1. In your earlier design, the "return to flat" feature of the boost and cut curves was a major design point and if I may quote from way back yonder, "Boosting 10Khz is one thing, but boosting 200Khz is quite another and can lead to some interesting stability problems". Other than perhaps additional complexity of design is there a reason why that approach wasn't incorporated here in the 2012 preamp ?
(I believe that some of todays "high end" sources such as SACD can apparently produce large amounts of HF hash outside the audio band, a format that I believe wasn't around back then).
2. The 2012 design while still using bipolar opamps seems to do away with all the AC coupling that was so obvious in the Precision Preamp. In that design it was to eliminate DC currents in the pot wipers and to give silent switching when the "tone defeat" relay was operated, something that appears not to be done here.
Is the DC question in practice a non issue here, given the lower impedances and so on ?
3. Finally, one of those NE5532 questions. Are all widely available examples (thinking manufacturers here) similar in performance ? There's always the usual "web chatter" about for example TI ones being inferior and the old Signetics being the best and so on. Is there any truth lurking there or not ?
You finished back 1996 asking whether that was the quietest preamp ever yet built. Perhaps that statement should be moved to the 2012 design
Hi,
Not particulary, actually. If people would have bothered to read the comments that where included with the Linestage/Tonecontrol schematic in the original thread they could have read:
However given that everyone was far too busy somehow finding reasons why the design I show (and which I cannot claim as mine as it is in the public domain for at least three decades) cannot be any good, even if those reasons had to be dragged over kicking and screaming by their hair, I took the liberty of calling the chemically pure bovine excrement as I saw it.
The OPA827 is rather nice on paper, in listening tests so far I have preferred OPA627/637 (especially 637, I use/reserve all my 627 Stock for DC Servo's), though this may be merely familiarity with their sound. They are some of the very few Op-Amp's I use in my own (as what I listen to) gear. I have yet to try the ADA4627, I did quite like the AD8610/20 for mods, especially the 8620, finally a dual worth having...
Ciao T
Not particulary, actually. If people would have bothered to read the comments that where included with the Linestage/Tonecontrol schematic in the original thread they could have read:
However given that everyone was far too busy somehow finding reasons why the design I show (and which I cannot claim as mine as it is in the public domain for at least three decades) cannot be any good, even if those reasons had to be dragged over kicking and screaming by their hair, I took the liberty of calling the chemically pure bovine excrement as I saw it.
The OPA827 is rather nice on paper, in listening tests so far I have preferred OPA627/637 (especially 637, I use/reserve all my 627 Stock for DC Servo's), though this may be merely familiarity with their sound. They are some of the very few Op-Amp's I use in my own (as what I listen to) gear. I have yet to try the ADA4627, I did quite like the AD8610/20 for mods, especially the 8620, finally a dual worth having...
Ciao T
Mooly,
DS addresses your 3rd question in his Active Crossovers book (great read btw).
Indeed it seems that not all 5532s are created equal.
Thanks, that's one I haven't read.
Mooly,
DS addresses your 3rd question in his Active Crossovers book (great read btw).
Indeed it seems that not all 5532s are created equal.
Which manufacturer for the 5531 ?
Pages 394-395.
"All measurements in this book were performed [...] to ensure worst-case results. "
All these measurements can be said to be already impressive.
And the availability and the price of devices from different manufacturers are certainly not equal.
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I'd say it's best if we don't "leak" any more info, unless DS himself wants to spill the beans.
The book is a nice investment - at least for ordinary people like most of us. I'm sure some will say they can spot good batches and/or manufacturers by ear, so I guess they can skip buying the book.
The book is a nice investment - at least for ordinary people like most of us. I'm sure some will say they can spot good batches and/or manufacturers by ear, so I guess they can skip buying the book.
Hi,
For anyone interested in the actual performance of Op-Amp's, Samuel Groner's extremely comprehensive measurements are a goldmine of free information that by far exceeds what is on offer for a fee:
SG-Acoustics · Samuel Groner · IC OpAmps
While the measurements are "non-standard" in the way they are made and presented, it is worth persevering with understanding them. They are quite eye-openers. For the rest, Samuel includes a brief and precise assessment of where the measured performance stands in the grand scheme of things.
His site also includes information on a number of discrete Op-Amp's (including ones routinely used in Pro-Gear) which are mostly also tested in the Op-Amp distortion mega-meta-test.
SG-Acoustics · Samuel Groner · Discrete OpAmps
Finally Samuel also has some most astute observations and comments on a certain (in)famous Book on Power Amplifier Design, well worth the read...
SG-Acoustics · Samuel Groner · Power Amplifiers
Ciao T
For anyone interested in the actual performance of Op-Amp's, Samuel Groner's extremely comprehensive measurements are a goldmine of free information that by far exceeds what is on offer for a fee:
SG-Acoustics · Samuel Groner · IC OpAmps
While the measurements are "non-standard" in the way they are made and presented, it is worth persevering with understanding them. They are quite eye-openers. For the rest, Samuel includes a brief and precise assessment of where the measured performance stands in the grand scheme of things.
His site also includes information on a number of discrete Op-Amp's (including ones routinely used in Pro-Gear) which are mostly also tested in the Op-Amp distortion mega-meta-test.
SG-Acoustics · Samuel Groner · Discrete OpAmps
Finally Samuel also has some most astute observations and comments on a certain (in)famous Book on Power Amplifier Design, well worth the read...
SG-Acoustics · Samuel Groner · Power Amplifiers
Ciao T
I know thats why i mentioned it would be nice if 827 did, i like them (cans) more for their looks if i'm honest; although i have read the now often repeated snippets from ex Nat-Semi employes claiming superiority for audio not just temp-co in the 150 degrees+ range
I like the 1641 a lot too, very versitile, great for Flea type low noise regulators too due to less than pernickety unity gain setup. most messing with opas i've been doing lately has been power train stuff
@Thorsten: no biggie mate, i just thought it worth mentioning as a lot of words have been spent on it (a bit like this post some might say). I havent tried the AD chip either as they dont have a samples program and its not really suitable for anything i'm looking to build anytime soon, so i havent picked any up to play with. Ive been distracted with the opa1632, opa1641/42/44, the old LT favorites 1028/1128 and 1007/37 and lme49990 lately as far as opamps go. the opa827 works very well as servo too, funny you mention it its the last time i used it; along with dac IV/transimpedance.
nothing wrong with the 'ol opa627, i just feel they are bettered for less money these days
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Hi,
It is an interesting chip, however it seems someone at TI forgot to include an output stage and stopped the design after the VAS... Of course, many of Kaneta's design use this style, so it probably is fine under most conditions.
For where the drive ability of the OPA1641 do not suffice the common emitter output stage with local miller feedback would seem to desire a FET buffer, rather than a bipolar buffer set to pull the output into single ended class A.
Price is quite low, so what is not to like. Now I have reason to get a new sample request to TI...
Ciao T
It is an interesting chip, however it seems someone at TI forgot to include an output stage and stopped the design after the VAS... Of course, many of Kaneta's design use this style, so it probably is fine under most conditions.
For where the drive ability of the OPA1641 do not suffice the common emitter output stage with local miller feedback would seem to desire a FET buffer, rather than a bipolar buffer set to pull the output into single ended class A.
Price is quite low, so what is not to like. Now I have reason to get a new sample request to TI...
Ciao T