Phono rig capacitance
Dfel, as I indicated earlier in the thread I can't speak too knowledgeably about modeling of SUTs. But FWIW the following thoughts occur to me: 1)Depending on how the simulation program you are using works, I think you might have to model the SUT as an "ideal transformer" combined with external elements representing its non-ideal characteristics (i.e., resistance, inductance, and capacitance, to the extent that they may be significant). 2)I would expect that the resistance of its two windings would be significant enough to warrant inclusion in the model, and that it should be modeled as two resistors external to the transformer itself, one of them in series with each of the windings. Or, alternatively, the resistance of the secondary winding could be modeled as reflected into the primary circuit, multiplied by the square of the primary to secondary turns ratio. 3)I don't know how you derived the inductances shown in your model for the two windings, but I suspect that they are not what should be included in the model. I believe that what should be included are series inductances in the primary and secondary circuits representing "leakage inductances." With the secondary circuit leakage inductance alternatively being modeled on the primary side, multiplied by the square of the primary to secondary turns ratio. 4)I don't know if it would be significant enough to warrant inclusion in the model, but including a parallel combination of resistance and inductance across the primary winding MIGHT also be called for, to account for core losses and reactances. (More precisely, those elements would be modeled directly across the primary winding if the impedances in series with the secondary are modeled on the secondary side; if the secondary side impedances are modeled as reflected to the primary side the reflected secondary side impedances should be modeled closer to the primary winding than those elements). Otherwise your model looks good to me. It assumes that the cable parameters are "lumped elements" rather than "distributed elements," but that assumption seems to me to be reasonable for present purposes. Regards, -- Al |
Dfel, Far be it from me to try to amplify on the advice you've been given by either Al or JCarr. However, I don't see where anyone answered your question re the typical range of inductance for a typical MC cartridge. In my personal experience, I have never heard nor read of any MC that has inductance as high as 1 mH. Nearly all MCs seem to have inductance in the low micro-Henry range, less than 100uH. The DL103 may be an outlier as regards MC inductance (don't know the numbers), because it also has a relatively high internal resistance, a sign that there is a large coil inside. Another source for information, if you are so interested in the math, is to be found on the Jensen Transformer website, in the form of a white paper on how to load their SUTs for flattest frequency response. Personally, I would just concern myself with impedance loading and be done with it, if I were to be using an MC with a SUT. In other words, let the capacitance and inductance take care of themselves, which will happen if you do nothing crazy, e.g., 10-foot ICs or weird phono input stages. |
Thanks Almarg, for you insight. as to the items: 1) In the K statement I have modeled it as a perfect SUT, this can be seen the by the 1 in the " K L2 L4 1". I can use numbers of less than one to make up for losses due to the SUT, like .6 .7 .9 etc..I figured lets see what happens with a perfect transformer first to isolate the cable effects. 2) Good point, I will sort that once I have the rest of the model making sense. I am concerned that the whole network of connections is completely modeled incorrectly. Can you please give some input on the basic structure, thanks. 3)Derived to have a 1:10 ratio, no other "genius" there (Strong emphasis on the quotation marks). The values I chose were arbitrary, so long as they had at square of quotient to give 10. Maybe that is incorrect. 4) I hear you, but I want to make sure that model itself I.E/ series/parallel resistors ground inductors and everything else are placed correctly in the circuit to model that part of a stereo system. I tried to follow Jcarr's model, but in the end I am still not sure why when modeling a wire connecting devices you would model the RCL in series or in parallel, and in what order you place the RCL for the wire connectors. I am a little lost on it and hoping someone can look at the images of the model circuit I have done and help me tweak it to the one that is correct. |
