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Cartridge loading - does it matter?
In article , Serge Auckland
wrote: Do you have figures for the inductance of a typical low-output MC cartridge. As far as I know, the coils are small, with very few turns, so I would have thought the inductance would be small. I don't have an inductance bridge to make the measurments. Compared with an MM cartridge who's coils are larger and have many hundreds (thousands?) of turns, I would have expected that the inductance of an MC would be small. My Goldring 1042 has a coil inductance of 570mH and a dc restistance of 660 ohms. My experience is that reviews and makers data tend to not give a value for the inductance of MC cartridges. The argument being that the value is 'small', so does not matter. However I have wondered about this. The main reason being that that although some MC's have 'low' output voltage and series resistance there is a tendency for the resistance to rise with the quoted output voltage. I therefore wonder if there is also a tendency for the inductance to rise with output level. Reason perhaps being that in order to get a 'high' output from an MC arrangement the temptation may be to simply wind many more turns and have a larger inductance coupled to the applied magnetic field. On that basis we might guess that a MC with a 0.3mV output for 5cm/s might have the order of a tenth of the inductance of a MM that has 3mV for the same velocity. This is just a surmise, though. However, since the inductance is in series with the generated output its significance may become greater when we have a low load resistance. So although the smaller inductance would be irrelevant for a 47k load, perhaps it is not for a much lower load? Dunno about the above as I've not used MC cartridges nor tested them at all. Slainte, Jim -- Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html |
Cartridge loading - does it matter?
On Sat, 14 Oct 2006 17:07:14 +0100, Nick Gorham
wrote: Don Pearce wrote: A very old and well used test record was my thinking. Not sure it would account for all of that. It is all on one channel - how convinced are you of the arm's bias setting? I am not, its on a new (to me) deck, and needs proper setting up. Thats my job for the weekend. Ah now - took me two days to do mine. Systemdek IV with an SME 3009II arm. True, but they will be tiny in comparison to the7-odd dB we are seeing from the resistive potential divider. What is the cartridge? It would be interesting to model the right parameters and see how close it comes. Its a Denon 301 that started this off. Can't find the numbers, unfortunately. d -- Pearce Consulting http://www.pearce.uk.com -- Posted via a free Usenet account from http://www.teranews.com |
Cartridge loading - does it matter?
In article , Nick Gorham
wrote: Ok, just had a look, Dennon 103, into Lundahl stepup at 1:20 (so its possible the change is as much down the the TX's as the cart). This is pink noise, with the 230R loading I use. http://www.lurcher.org/nick/audio/D103-250R.jpg And this is the same, with one chan down to 37R loading. http://www.lurcher.org/nick/audio/D103-37R.jpg I am not sure if I have followed what you have said above. Am I correct in assuming that by "1:20" you mean the transformer's nominal voltage step-up ratio? If so, are you using an amplifier connected to the secondary which has an input impedance of the order of 47k? if so, will this not put a present of the order of 1k at the primary? If so, I also wonder about the transformed level of capacitance seen at the primary. An alternative way to look at the above would be to note that - so far as the amplifier and cable on the secondary are concerned - the cartridge's source resistance and inductance will have been transformed by x40. Hence unless the coil inductance was very small, this might now lead back to loading problems of the type familiar to MM users. :-) When you refer to "230R" and "37R" above, do you mean these are the values you shunt the primary with? Or something else? Slainte, Jim -- Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html |
Cartridge loading - does it matter?
Actually, it was originally a question regarding loading a Sumiko Talisman
B. In response I offered my observations of my Denon 103s. "Nick Gorham" wrote in message ... Don Pearce wrote: .... Its a Denon 301 that started this off. -- Nick. |
Cartridge loading - does it matter?
On Sat, 14 Oct 2006 17:36:06 +0100, Jim Lesurf
wrote: In article , Serge Auckland wrote: Do you have figures for the inductance of a typical low-output MC cartridge. As far as I know, the coils are small, with very few turns, so I would have thought the inductance would be small. I don't have an inductance bridge to make the measurments. Compared with an MM cartridge who's coils are larger and have many hundreds (thousands?) of turns, I would have expected that the inductance of an MC would be small. My Goldring 1042 has a coil inductance of 570mH and a dc restistance of 660 ohms. My experience is that reviews and makers data tend to not give a value for the inductance of MC cartridges. The argument being that the value is 'small', so does not matter. However I have wondered about this. The main reason being that that although some MC's have 'low' output voltage and series resistance there is a tendency for the resistance to rise with the quoted output voltage. I therefore wonder if there is also a tendency for the inductance to rise with output level. Reason perhaps being that in order to get a 'high' output from an MC arrangement the temptation may be to simply wind many more turns and have a larger inductance coupled to the applied magnetic field. On that basis we might guess that a MC with a 0.3mV output for 5cm/s might have the order of a tenth of the inductance of a MM that has 3mV for the same velocity. This is just a surmise, though. However, since the inductance is in series with the generated output its significance may become greater when we have a low load resistance. So although the smaller inductance would be irrelevant for a 47k load, perhaps it is not for a much lower load? Dunno about the above as I've not used MC cartridges nor tested them at all. Slainte, Jim Jim, I've just been Spicing all the values I can find for both MC and MM cartridges with their appropriate requested loads, and I've found interesting things. The main one is that while MC carts are very forgiving of load - including cable capacitance, MM ones aren't. Indeed they look very marginal at the top end, varying from extremely peaky to badly rolled off depending on actual cable capacitance. They all see to be pretty marginal about getting to 20kHz at all. I've heard - and now read in places - that they achieve their top end frequency response by manipulation of a mechanical resonance and I can well believe it. Maybe this is why MC carts tend to have a top end spec that can extend to perhaps 60 or 70kHz. Have you done any similar sums? d -- Pearce Consulting http://www.pearce.uk.com -- Posted via a free Usenet account from http://www.teranews.com |
Cartridge loading - does it matter?
Jim Lesurf wrote:
In article , Nick Gorham wrote: Ok, just had a look, Dennon 103, into Lundahl stepup at 1:20 (so its possible the change is as much down the the TX's as the cart). This is pink noise, with the 230R loading I use. http://www.lurcher.org/nick/audio/D103-250R.jpg And this is the same, with one chan down to 37R loading. http://www.lurcher.org/nick/audio/D103-37R.jpg I am not sure if I have followed what you have said above. Am I correct in assuming that by "1:20" you mean the transformer's nominal voltage step-up ratio? If so, are you using an amplifier connected to the secondary which has an input impedance of the order of 47k? if so, will this not put a present of the order of 1k at the primary? If so, I also wonder about the transformed level of capacitance seen at the primary. Yes, the transformers turns ratio is 1:20. The secondary of this is connected directly to the grid of a E810F, and has a 100k resistor in parallel with the transformer secondary. The expected level of capacitance on the grid should be in the order of 3-4pf, the connections between the secondary and the valve base are no more than a few centemeter, so should add little additional capacitance. An alternative way to look at the above would be to note that - so far as the amplifier and cable on the secondary are concerned - the cartridge's source resistance and inductance will have been transformed by x40. Hence unless the coil inductance was very small, this might now lead back to loading problems of the type familiar to MM users. :-) I think you mean x400 there Jim. When you refer to "230R" and "37R" above, do you mean these are the values you shunt the primary with? Or something else? No, I mean the reflected load the source sees, from 100k and 15k loads on the secondary, If I said 230 it was a typo, the file name above gives the correct value. -- Nick |
Cartridge loading - does it matter?
Dish Guy wrote:
Actually, it was originally a question regarding loading a Sumiko Talisman B. In response I offered my observations of my Denon 103s. "Nick Gorham" wrote in message ... Don Pearce wrote: ... Its a Denon 301 that started this off. -- Nick. Sorry, my mistake, and I should have said 103. -- Nick |
Cartridge loading - does it matter?
Don Pearce wrote:
On Sat, 14 Oct 2006 17:07:14 +0100, Nick Gorham wrote: Don Pearce wrote: A very old and well used test record was my thinking. Not sure it would account for all of that. It is all on one channel - how convinced are you of the arm's bias setting? I am not, its on a new (to me) deck, and needs proper setting up. Thats my job for the weekend. Ah now - took me two days to do mine. Systemdek IV with an SME 3009II arm. Having said all that, the two chans only start to go odd over 14k, and thats sadly at the edge of my hearing now. The way the pink noise test track stops dead at 20k, make me think the source was digital. ot at least a CD AD/DA was in there somewhere. I am guessing what follows is the 2nd harmonic of what was below 20kHz. Not suggesting there is anything wrong with that, just an observation. -- Nick |
Cartridge loading - does it matter?
On Sat, 14 Oct 2006 22:45:41 +0100, Nick Gorham
wrote: Don Pearce wrote: On Sat, 14 Oct 2006 17:07:14 +0100, Nick Gorham wrote: Don Pearce wrote: A very old and well used test record was my thinking. Not sure it would account for all of that. It is all on one channel - how convinced are you of the arm's bias setting? I am not, its on a new (to me) deck, and needs proper setting up. Thats my job for the weekend. Ah now - took me two days to do mine. Systemdek IV with an SME 3009II arm. Having said all that, the two chans only start to go odd over 14k, and thats sadly at the edge of my hearing now. They start about 10kHz, and below that is a dip, so they might actually sound a little mellow rather than bright if your hearing is a bit down. The way the pink noise test track stops dead at 20k, make me think the source was digital. ot at least a CD AD/DA was in there somewhere. I am guessing what follows is the 2nd harmonic of what was below 20kHz. Not suggesting there is anything wrong with that, just an observation. Probably. d -- Pearce Consulting http://www.pearce.uk.com -- Posted via a free Usenet account from http://www.teranews.com |
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