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In Reply to: RE: opamps in phono stages posted by AudioSoul on August 25, 2014 at 13:44:31
That said, I still prefer discreet designs like Michael Yee's. His design for the Musical Surroundings Phonomena 2 proves good discreet designs don't have to be ultra expensive.
Some excellent info at his company's website (link below).
Opus 33 1/3
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I do not think the form-factor of an op-amp is any limitation to sound quality. In fact, they could potentially be outstanding because of low noise and short signal paths. But Design-wise, I doubt that any general-purpose op-amps are optimized for great sound (examples per the Michael Yee link).
IMHO the requirements for a business case for high volume production is the greatest limitation to op-amp quality for phono stages. Maybe this will change. Look what happened to Class D amps with ICE modules. Perhaps sooner than later we'll see really high-end designs with optimized components for phono stages?
"Knowing what you don't know is, in a sense, omniscience"
"I do not think the form-factor of an op-amp is any limitation to sound quality."
Actually there are issues. Big deal, there are issues with everything especially tubes.
But back to op-amps three pop to mind...
-Flexure sensitivity: The die could be used as a phono cartridge, stress alters offset voltages and generates internal voltage shifts.
-Thermal feedback: Clever die layout balances the thermal offset but not the loop gain variations due to carrier mobility changes.
-Noise/GBW tradeoff: Bigger geometries have less noise as it tends to average out, smaller geometries have wider bandwidth because they have fewer "strays" but individual carriers become a bigger part of the energy.
Perfection is a limit, not a possibility so you do the best you can with what you got. Good Engineers get good results. But that doesn't mean that tomorrow they won't do better or that things are bound to improve. That's just life...
One area where I do expect to see improvements is psychometrics. If we could really sort out how we hear and process music and our sensitivities to noise and distortion then the divergence between metrics and experience should substantially reduce making specifications a lot more useful. Actually without any additional knowledge components could easily be more fully specified which would really help audiophiles, but the former would do more for everyone.
Regards, Rick
We do try to fit solutions into existing paradigms. I like to think about alternative pickup mechanisms which do not involve moving a magnet through a coil. An optical cartridge with embedded IC comes to mind.
Interestingly, I think some manufacturers already have strong proprietary measurement tools that are highly tuned to assessing perceptual and experiential components of music experience via playback equipment. I've spent a part of my career doing perceptual testing and sensory testing, so I've seen some pieces of the process. These measuring tools are trade secrets. They are not widely shared with competitors (with the possible exception of the Canadian speaker consortium), much less the general public. But a great deal of perceptual testing has occurred and does impact on design and engineering goals within these organizations.
Unfortunately, since they are undisclosed, these measurements are not of use to us poor consumers trying to make decisions based on specifications.
"Knowing what you don't know is, in a sense, omniscience"
Regardless of the transducer principle, the 45/45 groove and the cutting procedure will dominate the final result.
I have an ELP (Laser Turntable) and the output is still fed to a phono preamp. This proved to my satisfaction that many of the distortions and blemishes that can be heard via conventional LP playback are often cut or embedded in the groove and not due to any stylus/cartridge design issues.
I guess the thread has deviated from the original point, but in my view the discussions around the phono stage ignore the more fundamental issues regarding the interaction of the transducers to the pre-amp electronics and other more dominant sources of distortion.
Regards Anthony
"Beauty is Truth, Truth Beauty.." Keats
"I like to think about alternative pickup mechanisms which do not involve moving a magnet through a coil. An optical cartridge with embedded IC comes to mind."
Well, you still would have a huge list of problems at the mastering and pressing end. Ultimately the solution to vinyl's problems is digital. No matter what you think of it's current state and implementation, the answer is still the same. It has it's own problems but theoretically they are all solvable to any desired limit while the mechanical ones are constrained by the structure and durability of the materials.
As far as the cartridge goes I recall that there already were capacitive or optical ones very long ago. I'm happy with my MM cartridge but think that a lot of it has to do with the blending of the various resonances in your turntable.
Regards, Rick
Good one--yes Michaels Design is excellent
Des
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