The 1350 ohms isn't the problem. It's the 400+ inductance. The quality of construction has nothing to do with using it as a reference source.If you are to pick a standard, the V15 at 1350R is an outlier and not the one to pick for a "measurement standard".
It is no longer made for a start. It's ancient and if you can find two V15 (II, III or IV etc) that have even remotely matched coil DCR/Ind from L to R, I'll eat them. The quality of Shure's internal construction is a joke, no precision at all. No consistency. It was bad enough before they moved to Mexico.
The world's largest selling cartridges by a clear margin is Audio Technica. They sell more in a year than all the other brands added up. They have been manufacturing the the AT-91 for at ~40 years and it is used in millions of turntables today, and the 3600L. I sold them back in the 1980s and 1990s as they were the same price as a replacement generic stylus. Not the best cartridge, but well made and more than good enough for most people. I wouldn't know how many tens of millions have been sold. It would be scary. The coil DCR/Inductance are very consistent for the stuff coming out of the Chinese AT factory. The new and 40 year old cartridges are pretty darn close, with the new Chinese ones being much more accurate channel to channel.
It has ~400mH and ~400R DCR.
It is currently measured here and at Stereophile with a very low source impedance which for this discussion is the same as shorting the input and measuring the noise at the output. Measuring using a low source impedance means the biggest noise contributor in an MM phono amp - the input noise current - flows through ~0 ohms and thus does not develop a noise voltage, which IS what happens if you feed it with a real-world MM source. You therefore end up with the bizarre situation that opamps like an AD797 or OPA1611 are quieter than an NE5532 or OPA1642 and so get ranked more highly for noise performance when in fact they are 7-10 dB worse when you connect a cartridge. You have to select the correct type of amplifier depending on the transducer you are using. For MC, you want very low noise voltage (so use an AD797 or OPA1611/12) and for MM, you should choose something with very low or negligible noise current and low noise voltage - so use an OPA1641/2 or NE5532/4 (these latter two have higher noise voltage than either the AD797 or the OPA1611/12Could you please clarify, how is SINAD actually measured ? With input shorted or with an MM attached ? According to reply you quoted the iFi Zen Phono has less noise with MM cartridge. However, the opposite is expected due to presence of input noise current ?
I don't want to see current noise specified. We are getting into technical details that probably most are not interested in unless they are designing low-noise analog circuits. I am suggesting that instead of measuring phono amps on this site directly out of an AP - which is a low source impedance - it is better to do it using a real-world MM source. @SIY has suggested just feeding the AP through the MM cart coils which seems a good approach to me. This will give a true reflection of the preamp noise performance when a cartridge is connected.The comment lives in between two worlds. For one it refers to objectively measured data in a well controlled environment, second it refers to subjective experience under utterly uncontrolled circumstances. Third you just speculate on something not measured, the current noise, which effect again depends on unspecified, widely varying properties.
If you like current noise to be specified, I support the inquiry.
Alas, I feel that I‘ve fallen out of the ongoing discussion. But anyway, equivalent current input noise is measurable, easy in my book at least, and as such could be used to estimate the impact of any generator impedance. That would not be possible when measuring the phono pre with just one real cartridge, and would need further calculations when using more than one. Besides the technical stuff, I strongly suggest to just play around, because vinyl is about that to the best of it. I‘m not on an irony ticket, I mean it. I loved my platter once for a reason. Can‘t put my finger on it, there‘s something about personal involvement hard to describe.I don't want to see current noise specified. We are getting into technical details that probably most are not interested in unless they are designing low-noise analog circuits. I am suggesting that instead of measuring phono amps on this site directly out of an AP - which is a low source impedance - it is better to do it using a real-world MM source. @SIY has suggested just feeding the AP through the MM cart coils which seems a good approach to me. This will give a true reflection of the preamp noise performance when a cartridge is connected.
Agree noise current is easy to measure and the total noise contribution will depend on the cartridge used. But, the 500mH + 1350 ohms I proposed is a good compromise since the 500mH L bit is pretty consistent with most mainstream carts and in the big scheme of things the 1350 DC coil resistance is neither here nor there - it will not materially affect the real-world noise measurement with a standard 47k load.Alas, I feel that I‘ve fallen out of the ongoing discussion. But anyway, equivalent current input noise is measurable, easy in my book at least, and as such could be used to estimate the impact of any generator impedance. That would not be possible when measuring the phono pre with just one real cartridge, and would need further calculations when using more than one. Besides the technical stuff, I strongly suggest to just play around, because vinyl is about that to the best of it. I‘m not on an irony ticket, I mean it. I loved my platter once for a reason. Can‘t put my finger on it, there‘s something about personal involvement hard to describe.
Sure, it is about the feel of it. Not to far in the past (digital) measurement was science fiction for most of us. Do we want to spoil the experience of personal preference in letting numerical ranking take over? Given the not always fully understood limitations, in all their variety, is measuring one or the other isolated data reasonable? There is so much not just right, all by at least one order of magnitude well objectionable (vertical tracking angle, horizontal tracking angle, degradation with the n‘th copy from a ‚mother‘, … ), hopeless and promising at the same time.Anyway, I concur there is a magic about T/Ts!
With the recent advent of low cost, quite stabile, low voltage noise opamps, current noise became an issue. MM data is affected, sure. With the X5‘s design one might argue that it is hard on the edge. But still it won‘t be easy to declare the data presented here misleading.(Perhaps the opportunity arises to re-measure those who offered very optimistic measures in mm in the same way to put things in perspective.)
I experimentally showed over a 20dB difference when using a MM cartridge impedance as a source compared with a low impedance source. Noise current is an issue that can be significantly reduced with design, but Johnson noise (both of cartridge and load) can't be. A few minutes playing with the cartridge Johnson noise calculator over on my website will demonstrate the importance of that factor.Add.: Look, the 1300 something Ohm DC won‘t do anything serious with noise current, the resonance from L/C at 10kHz or so is located where the preamp is 40dB below its max amplification, and it is narrow band, or low in reactive resistance. Plus the opamp is specified to be quite well behaved up to 10kOhm anyway (complicated because the reactive part dominates).
Maybe in a pathological educational example, but not here fore sure. You are stressing a point not in case. What else to say?***I experimentally showed over a 20dB difference when using a MM cartridge impedance as a source ….
Quite the opposite. A very standard phono preamp with a very standard MM cartridge. In this very thread (besides my original post in a different thread a couple years ago). I don't have a Fosi in house to demonstrate this, but I would expect a very similar result since it's physics driven.Maybe in a pathological educational example, but not here fore sure.
Come back when you can show this. Don't do math without considering RIAA equalization.Yes, very easy to do. I think the SINAD ranking on MM inputs on this site would change significantly.
No, it is up to whoever claims measurements change significantly. If they have never measured, then they can't make that assertion especially when simple things like mains leakage and equalization is not taken into account.It's more up to you to check your procedure....