You know, I'm not really a phono guy but reading all these phono pre articles in Linear Audio makes me start to think about it.
What I wonder: assuming that the hf ringing comes from mechanical ringing of the cantilever system. If we then damp the coil output to get rid of the ringing/overshoot, that's electrical damping, correct?
Meaning, the cantilever system merrily rings along, except we now don't see it in the electrical output? Or is my assumption incorrect?
jan
I'm going to make a logical guess about this, but I should think that the mecahical system would also be damped. I say that because if you electrically load down the output of an rotary electrical generator, the generator itself becomes a greater mechanical load for whatever is turning it. A phono cartridge, essentially being an reciprocating electrical generator, should experience the same sort of mecahnical loading or damping as a result of being electrically loaded or damped.
That sounds perfectly logical. Is that indeed the case? Somehow intuitively I can hardly imagine that tiny coil damping those mechanical vibrations - but my intuitions often are wrong.
Anybody has expertise about this?
jan
I understood we were talking about damping by loading with a (relatively) low impedance, sort of brute force.
jan
Jan, i think you talked about damping electronically IN THE CIRCUIT ( like Bob did ) and not loading the cartridge AT THE INPUT. That could be done too, i do that with loudspeakers all the time where i tame metal cones for example with series and parallel traps. I have not seen that done with MC cartridges though besides simple RC loading.
By the way, i think i will try it, good idea.
By the way, i think i will try it, good idea.
I believe Steven van Raalte did it in his Linear Audio Vol 3 article, loading the cartridge with 10.7k to dampen the response and electrically compensating later in the chain.
If I look at Bob's VinylTrak article in Vol 4 he appears to do the same.
He suggests a 6.7k load so that the roll-off with the cartridge inductance falls at the 75uS RIAA, so you have that EQ right at the cartridge.
jan
If I look at Bob's VinylTrak article in Vol 4 he appears to do the same.
He suggests a 6.7k load so that the roll-off with the cartridge inductance falls at the 75uS RIAA, so you have that EQ right at the cartridge.
jan
Most of us doing vinyl these days are using MC cartridges, they want a low R load, usually between say ~10ohms and ~100ohms... it seems to that while this load effects the HF response, it's hardly big rolloff, and in addition dropping the load down too low will also drop the already low output lower, so maybe not a good idea?
But, I am more interested in the ground discussion...
_-_-bear
But, I am more interested in the ground discussion...
_-_-bear
Joachim do you have any references on this stuff (I'll check the patent)? I would take the suspension to primarily damp the 8.5 Hz arm/cart resonance. I still don't believe the tip mass resonance gets any benefit of motor "braking".
Jan, although he does discuss the example of 500mH and 6.7k*, Bob stops short in his actual preamp design of realizing the 75us entirely at the cartridge. Last sentences of 4th paragraph pg. 137 LA #4: "There is also a S/N penalty. Perhaps a compromise is in order."
Based on the model presented for the V15, 370mH in series with 830 ohms, the appropriate value for an external resistor to realize a 75us tau would be 4.103k ohms (a total R of 4.933k ohms). That value using a real resistor adds significant thermal noise, particularly at high frequencies, and also causes some attentuation.
Cordell's compromise is a load of 18k ohms, and he compensates in the stage response.
Brad
*Note that the article does not mention that the 6.7k is the total resistance, as the example is just for 500mH with no internal resistance.
We will come back to this I promise you.
But you guys want to go back to grounding, I don't want to hijack this.
jan
Inclined to agree (in the absence of data
). The coupling between cantilever etc. and motor is probably not that great.Van Raalte in LA #3 "Correcting Transducer Response with an Inverse Resonance Filter" shows no electrical-mechanical interaction. The mechanical resonance is represented by a two-pole lowpass filter with a low-Z output, which in turn drives the cartridge equivalent electrical circuit (see pg. 83, Fig. 11). I suspect that's an oversimplification, but perhaps a small one.
Van Raalte gives appropriate credit to van Maanen* for discussing the compensation approach in an article from 1980. It would be nice if someone would translate that from the Dutch.
This "New Old Thing" of overdamping the cartridge is interesting, but so far I haven't read any reports of how it sounds, and I tend to view second-guessing of cartridge designers with some trepidation. Particularly when theoretical transient response results are presented as if they must entail better sound on the face of it, things cry out for actual listening. With really good test records at least the confounding variable of a change in frequency response can be determined.
Brad
*Signaalprocessor voor Magneto-dynamische Pick-up elementen", Radio-Elektronica 80, 19, pp. 39-53 (1980).
Maybe a new thread on overdamped cartridge loading? The grounding discussion is already off topic to some extent.
Inclined to agree (in the absence of data
Van Raalte in LA #3 "Correcting Transducer Response with an Inverse Resonance Filter" shows no electrical-mechanical interaction. The mechanical resonance is represented by a two-pole lowpass filter with a low-Z output, which in turn drives the cartridge equivalent electrical circuit (see pg. 83, Fig. 11). I suspect that's an oversimplification, but perhaps a small one.
Van Raalte gives appropriate credit to van Maanen* for discussing the compensation approach in an article from 1980. It would be nice if someone would translate that from the Dutch.
This "New Old Thing" of overdamping the cartridge is interesting, but so far I haven't read any reports of how it sounds, and I tend to view second-guessing of cartridge designers with some trepidation. Particularly when theoretical transient response results are presented as if they must entail better sound on the face of it, things cry out for actual listening. With really good test records at least the confounding variable of a change in frequency response can be determined.
Brad
*Signaalprocessor voor Magneto-dynamische Pick-up elementen", Radio-Elektronica 80, 19, pp. 39-53 (1980).
Van Maanen*, in his Vol 4 Guest Editorial sort of sideways refers to an A/B test he did on this with listeners deciding within 30 secs that the overdamped/eq'd case was clearly better sounding. But without further info it's hard to know what exactly was tested, of course.
jan
*"The case for subjective listening tests", H van Maanen, Vol 4
Before leaving the subject -- I designed a simple 4 transistor MC pre-preamp circuit that used complimentary grounded base input... with gnfb the input Z (cart loading) was very low. Cartridge going direct to emitters for input. The distortion from the cartridge was lowered. Sounded great. [published circuit topology in TAA about a million years ago] Thx-RNM
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Yes, hard to know indeed. We know frequency response is audible, even under the stresses of DBT. The test signals he mentions for example in LA Vol. 4 that were easy to use to distinguish the differences between MM and MC cartridges are pathological ones ("two single period 18kHz tone bursts, separated by a half cycle"
).The statement is made that in blind A/B testing the listeners noted the improvement in 30 seconds, which does not sound like only the effect of phase response. And as well, for the overdamped versus normal comparisons, how many copies of a given LP were used by the good Doctor to ensure that changes to the medium per play were small and of negligible importance, when his listeners started evaluating the mechanical resonance compensation? I guess I'd better learn Dutch. He gives a link to these: Temporal Coherence .
Having said that, I think overdamped as an option is here to stay. Let the listeners decide. It's highly nontrivial, since the appropriate values for damping R, loading C if any, and subsequent EQ, are cartridge-specific.
Also, van Maanen supposes that no scientific comparisons have ever been made between MM and MC. As I remarked previously, there was a small test done at NRC many years ago, and when the three cartridges were equalized for frequency response (not via overdamping etc. which was not explored), the listener preferences became mostly a wash. When the identities of the cartridges were revealed there was much soul-searching, since some had bad-mouthed the V15 in advance. They did not know the identities going in, but most were completely convinced that MC was per se better. Of course the associated electronics were cited as the confounding effect, by those desperate to maintain their preconceptions.
I'm working on Toole to at least include the articles in a Opera Omnia
Scott, i have not found the patent yet but here it is mentioned at least.Phono Pre-Amplifier P-75 mkII
Similar to the Marshall Leach design? Actually if GNFB was included it would be a departure from ML. Roughly what year in TAA?
The ML design, which at times was not credited properly, had the feature of a floating power supply, a device to eliminate any net d.c. flowing in the cartridge. It's lived on here and there, sometimes operated at too-low currents for good noise performance. The JFET common-gate versions are in another thread or two in here.
Concerning measurements, this may be interesting.Amplitude And Energy Correction ? A Brief Summary : Noise & Vibration Measurement Blog