Given that owdeo's hearing the distortion that's sufficient to be certain that they are. What leads you to consider that audible distortion might be of no consequence?
Ironically the first sentence here is a bunch of nonsense. That is until the meaning of 'sound signature' applied to an opamp (in isolation from circuit context) is explained.
Agreed - the Self '96 preamp represents the sound of an NE5532?! Talk about missing the point - that is utter nonsense. An illogical piece of obstructive propaganda! The 2012 design must therefore represent the sound of the NE5532 mixed with the LM4562...
I have certainly found the 5532 to sound innocuous in other designs. Of course it depends on how and where you use it.
Incidently I really dislike the LM4562 in every design I've tried it in. But the LME49710 (the single version of it) is pretty darn good. The NE5534 sounds better than the 5532 when I've compared in similar configurations too. Would anyone agree that singles are generally better than duals? This is another of those subjective things that doesn't seem to be revealed by THD+N curves...
I like your theory on input degeneration Abraxalito - this makes a lot of sense. I found when tweaking the discrete preamp circuit that this was critical - once I got it right, everything just seemed to snap into focus. And one of my favourite power amps, the Leach amp, has lots of input degeneration to keep the GBP to a designed figure and minimise TIM (as it was called then). I'm starting to see a pattern...
Thanks for sharing your views on the OPA2604 Bob - indeed it is comforting to know that someone of your expertise finds it good both technically and subjectively, regardless of absolute THD figures.
I have certainly found the 5532 to sound innocuous in other designs. Of course it depends on how and where you use it.
Incidently I really dislike the LM4562 in every design I've tried it in. But the LME49710 (the single version of it) is pretty darn good. The NE5534 sounds better than the 5532 when I've compared in similar configurations too. Would anyone agree that singles are generally better than duals? This is another of those subjective things that doesn't seem to be revealed by THD+N curves...
I like your theory on input degeneration Abraxalito - this makes a lot of sense. I found when tweaking the discrete preamp circuit that this was critical - once I got it right, everything just seemed to snap into focus. And one of my favourite power amps, the Leach amp, has lots of input degeneration to keep the GBP to a designed figure and minimise TIM (as it was called then). I'm starting to see a pattern...
Thanks for sharing your views on the OPA2604 Bob - indeed it is comforting to know that someone of your expertise finds it good both technically and subjectively, regardless of absolute THD figures.
Yeah - its distortions are fairly subtle, so long as its not provoked by RF.
I only tried it once, disliked it badly enough to not bother trying it (ever) again. Its much more RF sensitive than NE5532 it seems.
To help with further pattern forming, have a look at this paper I discovered a few weeks ago (if you haven't seen it already) : http://www.diyaudio.com/forums/analog-line-level/146693-john-curls-blowtorch-preamplifier-part-ii-657.html#post3330996
I don't see that at all, Bob seems to be refering to blindly reducing the feedback network impedance to lower noise without considering the increased load on the output stage. He's criticizing a design process not anyone in particular.
I have a hypothesis that the capacitance to the metal can with those parts is acting as a low-pass filter on the -ve and +ve inputs. Rather like how a feed-through capacitor works, so the SQ improves. A cheaper option would be to use an inductor and resistor passive filter on those sensitive pins, but its possible the screening effect of the can plays a part too.
Richard
You may be correct, but the metal can version gets warm enough when used with + and -15V rails, for many people to feel the need to fit a heatsink.
Considering that the internal chip is identical, then the poor DIP8 version must feel like it is wearing an overcoat !
Regards
Alex
I don't think loading the output of the DAC opamp with 200R is likely to give good results, and certainly not an example of what the sound of "no preamp" is like. Whatever impedance attenuator you choose is going to be a compromise one way or the other.
As for level control in the digital domain - you are kidding aren't you?! You want to throw away those bits? You are suggesting this could this be better than having a preamp in the system?
The sound of no preamp... sounds like some kind of Buddhist quest to me
Thanks - pretty heavy stuff though! I also recently read Walt Jung's paper on opamp input degeneration or lack thereof.
What I don't see is where all this RF is coming from in a typical living room. Perhaps some remaining switching artifacts from the upstream DAC that aren't filtered out by its output stage active filter. But all the designs I've tried those opamps in have passive LP filtering at the input. Hang on though, the Self '96 design doesn't...
Have tremendous respect for Doug Self, if it wasn't for his work I would have never started in this insane hobby. However over the years I have learned that his foundation is essential for the quest for better measuring audio designs, but the human concept is missing. It is the designers willing to take chances that often end up hitting the mark, any monkey with some knowledge can design for low Thd which is consistently done with heavy negative feedback, and many components. Until we have implants in our brains to receive audio there will always be imperfections, of course the thd is important in a distribution aspect but I guarantee the amp with 1 percent h2 could sound even closer to the source than .0001 percent. I did the blameless thing, always left me wanting on the musical front .
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I've built two preamps using this device, and it's single equivalent. I've measured the one design on an AP and the results are very good. I also built (on Veroboard) an experimental class A buffer using the 4562 as the driver to a discrete output stage and measured that on an AP. I listen to the preamps regularly and they are very open with great sound staging. So when people tell me so and so opamp is no good or I sounds bad I always wonder about their implementation.
I have a 200 MHz band width analog cope and a 1GHz DSO. You'd be amazed at the things you see that just don't show up with a 20MHz scope, or in some cases, builds where the individual has no access to decent equipment.
I'm not going to get into an argument about the sound of opamps (and they do sound different), but I am very skeptical about some of the comments. It's like the story about the PGA23xx devices. . .
I have a 200 MHz band width analog cope and a 1GHz DSO. You'd be amazed at the things you see that just don't show up with a 20MHz scope, or in some cases, builds where the individual has no access to decent equipment.
I'm not going to get into an argument about the sound of opamps (and they do sound different), but I am very skeptical about some of the comments. It's like the story about the PGA23xx devices. . .
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Aren't we being just a tad melodramatic?.....As for level control in the digital domain - you are kidding aren't you?! You want to throw away those bits? You are suggesting this could this be better than having a preamp in the system?
The sound of no preamp... sounds like some kind of Buddhist quest to me
I won't to go into the increasing pivotal role of DSP or even electronic volume controls in the recording and production of digital media,
as you are obviously sold on Analog controls in your domestic environment. I just don't buy the analog arguments any more, even from my
own, sometimes inconclusive listening tests, and some have been with quite expensive gear; well beyond my budget.
If you are more interested in discussing the possibilities than investigating the differences between the preamps, that's fine, no problem.
This was quite informative regarding digital volume controls,
Rocky Mountain Audiofest 2012
This is now a dead link as the content seems to have been taken down.
Rocky Mountain Audiofest 2012
This is now a dead link as the content seems to have been taken down.
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Common-mode noise via mains transformers is one - capacitively coupled between primary and secondary windings. Common mode pick-up of airborne RF on the shields of interconnect cables is another.
RC passive filtering only gives 20dB/decade filtering. Say typically there's a pole at 200kHz to maintain 0.1dB flatness at 20kHz. Then your rejection is only 40dB by 20MHz. Many DACs nowadays have OOB noise in the 100kHz to 3MHz range which barely gets attenuated under such schemes. But IME the main noise issues concern the noise on grounds - then the RC filter is actually making matters worse by providing a low impedance path for ground-borne noise to enter the opamp's input.
Thanks Mooly - an excellent presentation on both subjects. I think he could have taken into account more with the comparison between D and A volume controls that quantisation noise is going to be far more objectionable than thermal noise, so the analogue control still comfortably reigns supreme even if you happen to have a DAC with twice the resolution of your source to avoid throwing away bits.