100 ohms is a default value normally used as a design reference for cartridge designers. In fact, in my latest phono preamp design, it is the selected value for the vast majority of MC cartridges. However, 47K is an alternate load value that many MC designers often adjust their cartridge for. Any other value is really 'accidental' or just a product in the design compromises in the cartridge design in order to optimize some other quality, tracking for example. In these examples, external loading often is more obvious in measurements, as internal damping is often removed to improve other measurements. Still, it is not a great difference, and sometimes not really worth the compromise in S/N and absolute output. However, for the vast majority of MC cartridges, with a relatively flat frequency response, inherently, there is little change in output with a large change in cartridge loading.
Now where does this leave us? It would seem that Syn08 has put in an elaborate loading scheme in order to please the manufacturer's recommendations, virtually exclusively. Even if others might find a value slightly different from the manufacturer's spec. (which is often arbitrary and vague as well) to sound best. Often, this happens over a relatively limited range of loading resistance, for example 50-150 ohms for example. It depends on the cartridge. Over the years, optimum loading resistance appears to have gone up in value, leaving 50 ohms behind, 100 ohms as a nominal optimum, and higher values from 150 ohms all the way up to 47K ohms as a good choice for many MC designs.
This is where the PhD's and the golden ears differ. The 'golden ears' just listen, and if they have the ability to change the loading, they will find one, in almost every case. It might be 68 ohms with one cartridge, and 150 ohms in another, and even 47K for some. It will be relatively obvious when you have the 'optimum' loading and yet the measured change will often be minimal. This is what separates the subjective from the 'objective'. The 'objective' designers will put in variable loading, just in case, without regard to its actual value as a listening optimizer, unless the particular cartridge, they are using, is unusually sensitive to it, and they note this at some point in the design of their phono reproduce stage.
Now where does this leave us? It would seem that Syn08 has put in an elaborate loading scheme in order to please the manufacturer's recommendations, virtually exclusively. Even if others might find a value slightly different from the manufacturer's spec. (which is often arbitrary and vague as well) to sound best. Often, this happens over a relatively limited range of loading resistance, for example 50-150 ohms for example. It depends on the cartridge. Over the years, optimum loading resistance appears to have gone up in value, leaving 50 ohms behind, 100 ohms as a nominal optimum, and higher values from 150 ohms all the way up to 47K ohms as a good choice for many MC designs.
This is where the PhD's and the golden ears differ. The 'golden ears' just listen, and if they have the ability to change the loading, they will find one, in almost every case. It might be 68 ohms with one cartridge, and 150 ohms in another, and even 47K for some. It will be relatively obvious when you have the 'optimum' loading and yet the measured change will often be minimal. This is what separates the subjective from the 'objective'. The 'objective' designers will put in variable loading, just in case, without regard to its actual value as a listening optimizer, unless the particular cartridge, they are using, is unusually sensitive to it, and they note this at some point in the design of their phono reproduce stage.
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Almost 100% agreed. If it takes only few extra resistors and caps to potentially make a large percentage of the GEB population happy, by allowing them to tune the input impedance to their perfection, then I'm 100% in. This is usually called "flexibility". Of course, there will always be a nonzero percentage of unhappy GEB members, because the wiring is teflon, and not unbleached cotton, insulated.
BTW, don't forget that the DIP switches I am using are not 1-of-n. You can parallel the resistors and caps to a wealth of input impedance combinations.
BTW, the Pass XONO uses the same variable input loading approach, using the same kind of DIP switches.
Now to address important aspects of test records. The 'standard' square wave test record in my day, was the 'CBS STR 112 Test Recdording' made decades ago. Virtually all square wave tests that I have seen published, are based on this record. However, this record was apparently made long ago, when disc cutter resonances were limited and undamped (in order to meet some sort of high frequency output spec. apparently) so they cut (recorded) the record at half speed, in order to get the bandwidth up. This left a distinct ringing at about 40KHz on the square wave.
This did not easily show up on the vast majority of phono cartridges of the day, because they were essentially 4 pole roll-off filters at just about 20KHz, so the extra ringing would not show up on the scope. As MC cartridges became more popular, in later years, this ringing appears much more pronounced and makes the interpretation of what you see, difficult without an experienced eye, as you have 2 separate high Q resonances contributing to the output. SY has shown how you can separate the two resonances from each other by changing the turntable speed.
This did not easily show up on the vast majority of phono cartridges of the day, because they were essentially 4 pole roll-off filters at just about 20KHz, so the extra ringing would not show up on the scope. As MC cartridges became more popular, in later years, this ringing appears much more pronounced and makes the interpretation of what you see, difficult without an experienced eye, as you have 2 separate high Q resonances contributing to the output. SY has shown how you can separate the two resonances from each other by changing the turntable speed.
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I though you are supporting the idea of NOT having a variable input impedance.
Otherwise, of course, it was done 40 years ago
BTW, did I claim anything?
I don't see the logical fallacy, this happens in reality a lot, in other fields too. It's not a big deal not being able to measure something, why not accept it when it happens? Look at how many years they were trying to measure what makes a Stradivarius sound as it sounds. Very obvious audible differences between two violins, yet very difficult to measure what gave one that special sound.
Not that it matters, but I have no allegiance as far as audio philosophy goes; that warm fuzzy feeling I get when I see integrity, fairness, kindness, generosity. Whether they are great designers or not is not important to me.
True, you don't owe me any answers, nor does anybody else. If at all, I think you owe it to yourself. Hundreds of people read this forum, for many years to come. Unfortunately, the sum of your answers is syn08 for them.
syn08, I actually appreciate your technical input (my case of beer offer stands). The way you deliver it is a another story. Absolutely nothing gives anyone the right to put other people down. The same goes for other people too. Just because it's popular it doesn't mean it's right. Perhaps you don't mean it, but you do it quite a lot. That I don't appreciate.
Case in study was the impact of the resistive loading on the cartridge frequency response. After calibrating the levels @1KHz, measurements are showing nothing outside the experimental errors.
Assuming there would be a difference in the subjective perception between, say, loading with 100ohm and 500ohm, then there are two options:
a) the measurements are wrong - end of discussion.
b) the subjective differences are due to another cause - end of discussion, it's outside the scope of the experiment.
Otherwise, if you think there's a possibility to hear a frequency response change that is buried in 0.1 dB noise, then this is (to me) a logical fallacy. Like it or not, I do not address such. Other may, though, therefore my recommendation to go elsewhere.
Thanks for the beer, I already had my six pack quota for the year of 2009.
Perhaps a digitally controlled variable resistor
. Maxim/Dallas and TI are offering quite a few.
Since people don't listen to the cartridge itself, let's put the preamp in the chain too. Then there's the possibility that the preamp responds differently to various cartridge loading which would account for people being able to hear the difference.
So, I may not hear the difference burried in 0.1dB noise, but the preamp may very well filter inadvertently the noise. The other possibility is that the brain filters out some of the noise, but that I know nothing about.
Sure, you may also consider the power amp, the speakers, the outside weather and the phase of the moon.
This isn’t accurate, I referred to limited budget on recording gear, not measuring equipment. Anyhow, what measurements, by themselves, do you think will be able to tell the sound quality of any amp?
Without actual examples, this is meaningless.
Those numbers refer to best case listening environment.
The 7th harmonics is unique, for it doesn't appear in nature. No natural musical instrument or sound producing device has 7th harmonics. Experience and experiments show that the human ear finds 7th harmonic extremely objectionable.
Also, scientific experiments show that the human ear is sensitive to distortion in frequencies far above 20 KHz, though not to fundamentals.
Not at all. Lower THD figures are easily achieved with NFB and GNFB. When large amount of NFB is applied without proper consideration of the appropriate Slew Rate, measurements of THD will be excellent, while the sound will be bad.
That's assuming you don't do something silly like compare a tube amp to a solid state amp on THD specs alone. Now that is a pretty meaningless exercise if you ask me!
Since when measurements affects tube amps differently than SS ones?
The bottom line is that the measurements most relevant to sound quality are never published. Hence, it's impossible to tell the sound quality of an amp by its' published measurements alone.
I don’t agree about published specifications being able to tell the sound quality of an amp. Please give examples to demonstrate your claim.
There are wrong assumptions on your part. When I (and some others I know) compare pieces of audio gear, be it amps, or cables, or anything, we do it with double blind tests, so that brand and price are unknown as long as the test goes on.
As for integration, you are right. However, it's my experience that certain loudspeakers and certain amps sound much better than others in any audio setup.
Self fulfilling prophesy now.
In truth, you should listen to all well designed, well made equipment in your price range. For example, Nelson Pass has designed commercially successful equipment that are different in the most fundamental ways. To do anything else is simply to restrict your choices, but then that is your problem.
It’s impossible for me to listen to all well made equipment, in any price range. Some brands aren't being imported to my country. Other brands that are being imported, the local dealers don't have gear to demonstrate, they import only what's ordered and paid for in advance.
That's not applicable to those designers who maintain that only measurements are relevant, while "refined listening" or "golden ears" are only marketing snakes oil.
Did I say anywhere I follow blindly the manufacturer's recommended load?
If b) is correct and there are subjective audible differences that as for today we don't know how to measure, why stick with measurements alone, without supplementing it with listening tests?
I'm going to dismiss the weather and phase of moon snide remark. You already assumed audible differences:
If your assumption is correct and you can hear the differences in loading (and that is what I asked you initially, but you chose to dodge the answer using logical intricacies) they must come from somewhere, even if you can't measure them. Either from the cartridge, or somewhere else down the chain. Otherwise you've heard things just like the rest of them delusional audiophiles
If your assumption is correct and you can hear the differences in loading (and that is what I asked you initially, but you chose to dodge the answer using logical intricacies) they must come from somewhere, even if you can't measure them. Either from the cartridge, or somewhere else down the chain. Otherwise you've heard things just like the rest of them delusional audiophiles
Lots of examples of seventh harmonic in acoustic instruments.
There's life above 20 kilohertz! A survey of musical instrument spectra to 102.4 kHz
What is a Sound Spectrum?
This is also the case for singing. See, for example, "Musical Instruments: History, Technology, and Performance of Instruments of Western Music," Campbell, Greated, and Meyers, p 35.
Another urban legend bites the dust.
There's life above 20 kilohertz! A survey of musical instrument spectra to 102.4 kHz
What is a Sound Spectrum?
This is also the case for singing. See, for example, "Musical Instruments: History, Technology, and Performance of Instruments of Western Music," Campbell, Greated, and Meyers, p 35.
Another urban legend bites the dust.
If your assumption is correct and you can hear the differences in loading (and that is what I asked you initially, but you chose to dodge the answer using logical intricacies) they must come from somewhere, even if you can't measure them. Either from the cartridge, or somewhere else down the chain. Otherwise you've heard things just like the rest of them delusional audiophiles
I made absolutely no assumptions about any audible effects of cartridge resistive loading. You are perfectly free to design and perform another better test that would reveal and explain the subjective testing results. If it makes sense (nobody can afford to test any possible permutation of factors, moon phase included) you may even get some support in your endeavour.
Or you may chose to happily live ever after, without results and explanations, like so many other contributors here.
This is not normally true, Joshua. Assuming that you mean that the amp has insufficient slewrate, that would surely show up in THD measurements, especially done at higher frequencies. That is one reason why Bob Cordell for instance advocates THD-20 measurements. I agree that 1kHz measurements have much less chance to turn up the effects of insufficient slew rate, but a designer who is aware of these issues would use measurements that would show it.
One example of 'looking at the schematic and know how an amp sounds' is this. You can often see from the circuit diagram whether the slewrate is sufficient or not (not always, but sometimes), so that would be a good indication that that amp wouldn't sound like the best ones out there.
jd
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