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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 |
Cartridge loading - does it matter?
In article , Don Pearce
wrote: 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. The above is generally so in my experience. Certainly the Shure MM cartridges tend to exploit cable capacitance and have a response that is very load-dependent - due mainly to their inductance. 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? Not really. When I was interested in this topic (mainly 20 years ago :-) ) I lacked the data on details like MC coil inductance. Hence I've only been able to do some generalisations. The snag being that this may all be specific to individual set-ups, etc, so the generalisations may simply not apply in many cases. I suspect that the resistance and inductance tend to scale with the output level. This would mean that most MCs have a much lower inductance than a MM as their output is much lower. But I don't know how reliable such an assumption may be. Although reviews dismiss the inductance of MCs as being too small to matter. I am not sure this is always the case. The example here is the use of a transformer. A voltage step-up of x10 will cause the source impedance seen by the amplifier to change by x100. Thus, unless the MC has an inductance which is well below 0.01 that of a MM, using a transformer might then lead pun to similar effects as with an MC. The above problem won't show up with a transformerless system. However since the inductance is in series with the EMF, it may still matter if the amplifier input impedance is far lower than is typically used with a MM. I'd be interested in the details of the models you have done, and the source impedance data, etc. Do you take cabling into account? 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?
In article , Nick Gorham
wrote: Jim Lesurf wrote: 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. OK. I assume what what you say that you avoided co-ax between the secondary and the grid. 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. Yes, sorry about that. I did a quick calculation based on x400. Then when I started my email decided I must have made a mistake and changed to x40 (which was wrong). A minute after sending the posting I realised my error. :-) 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. Again, I suspect the "230" was my error/typo. Probably another manifestation of my brain not being in gear when I posted. :-) The point this raises is that - despite the magazine reputation of MCs that they are not 'load sensitive' - they may be in practice, particularly when using a transformer or an amp with a low input impedance. Thus reviews really should give source resistance and inductance values in my view. Are there any figures for things like the capacitance levels, or other imperfections of the transformer you use? I ask because many years ago I did experiment with using step-up transformers for MC input but abandoned this in favour of a low-impedance low-noise preamp. The main reasons being risk of hum induction and transformer capacitance, etc, introducing source and load dependent variations in response. This was 20+ years ago, though, and the transformers I had to try may well have been much poorer than modern ones. I was also curious about the apparent difference in channels with the lower load as shown in your plots. 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 Sun, 15 Oct 2006 09:40:12 +0100, Jim Lesurf
wrote: Although reviews dismiss the inductance of MCs as being too small to matter. I am not sure this is always the case. The example here is the use of a transformer. A voltage step-up of x10 will cause the source impedance seen by the amplifier to change by x100. Thus, unless the MC has an inductance which is well below 0.01 that of a MM, using a transformer might then lead pun to similar effects as with an MC. The above problem won't show up with a transformerless system. However since the inductance is in series with the EMF, it may still matter if the amplifier input impedance is far lower than is typically used with a MM. I'd be interested in the details of the models you have done, and the source impedance data, etc. Do you take cabling into account? Slainte, Jim Jim, A quick google on mc cartridge inductance yielded a small crop. An Audio technica gave 70uH in series with 17 ohms, and a load of 20 ohms or more. Another, the Eroica, is 12uH with 8 ohms so there is quite a variation. As you say, the inductance tends to go hand in hand with output level. I have made the same search for mm cartridges, and come up with typical values around 500mH. My model was simple - a voltage source in series with the L and C, and a load resistor in parallel with the cable capacitance. Again I looked around the various arm assemblies to find typical values, as well as the recommended values. As I say, what I found was that you can take huge liberties with the loading of mc cartridges and the only effect is on the level. The same is not so for mm cartridges, which appear highly resonant with cable capacity at the top end. The question of transformers for mc carts is interesting. A transformer will multiply the capacitance as it divides the resistance, so it needs to go at the amplifier end of the cable, not the cartridge end if many nanofarads aren't to be dropped across the cartridge. d -- Pearce Consulting http://www.pearce.uk.com -- Posted via a free Usenet account from http://www.teranews.com |
Cartridge loading - does it matter?
"Don Pearce" wrote As I say, what I found was that you can take huge liberties with the loading of mc cartridges and the only effect is on the level. Been waiting for that to show - it's all I know about the subject....!! :-) The question of transformers for mc carts is interesting. A transformer will multiply the capacitance as it divides the resistance, so it needs to go at the amplifier end of the cable, not the cartridge end if many nanofarads aren't to be dropped across the cartridge. Again, interesting to know - but I bet it's near enough impossible to tell.... |
Cartridge loading - does it matter?
Jim Lesurf wrote:
Again, I suspect the "230" was my error/typo. Probably another manifestation of my brain not being in gear when I posted. :-) That was my typo, seemd to be a bad day for them yesterday. The point this raises is that - despite the magazine reputation of MCs that they are not 'load sensitive' - they may be in practice, particularly when using a transformer or an amp with a low input impedance. Thus reviews really should give source resistance and inductance values in my view. Are there any figures for things like the capacitance levels, or other imperfections of the transformer you use? I ask because many years ago I did experiment with using step-up transformers for MC input but abandoned this in favour of a low-impedance low-noise preamp. The main reasons being risk of hum induction and transformer capacitance, etc, introducing source and load dependent variations in response. This was 20+ years ago, though, and the transformers I had to try may well have been much poorer than modern ones. This is all I have http://www.lundahl.se/pdfs/datash/9206.pdf -- Nick |
Cartridge loading - does it matter?
On Sun, 15 Oct 2006 15:19:41 +0100, "Keith G"
wrote: "Don Pearce" wrote As I say, what I found was that you can take huge liberties with the loading of mc cartridges and the only effect is on the level. Been waiting for that to show - it's all I know about the subject....!! :-) The question of transformers for mc carts is interesting. A transformer will multiply the capacitance as it divides the resistance, so it needs to go at the amplifier end of the cable, not the cartridge end if many nanofarads aren't to be dropped across the cartridge. Again, interesting to know - but I bet it's near enough impossible to tell.... Maybe.... more sums for me later. d -- Pearce Consulting http://www.pearce.uk.com -- Posted via a free Usenet account from http://www.teranews.com |
Cartridge loading - does it matter?
On Sun, 15 Oct 2006 14:49:24 GMT, (Don Pearce)
wrote: On Sun, 15 Oct 2006 15:19:41 +0100, "Keith G" wrote: "Don Pearce" wrote As I say, what I found was that you can take huge liberties with the loading of mc cartridges and the only effect is on the level. Been waiting for that to show - it's all I know about the subject....!! :-) The question of transformers for mc carts is interesting. A transformer will multiply the capacitance as it divides the resistance, so it needs to go at the amplifier end of the cable, not the cartridge end if many nanofarads aren't to be dropped across the cartridge. Again, interesting to know - but I bet it's near enough impossible to tell.... Maybe.... more sums for me later. d As I sort of suspected. Adding the transformer makes the mc more susceptible to capacitance following the transformer, but not preceding it. d -- Pearce Consulting http://www.pearce.uk.com -- Posted via a free Usenet account from http://www.teranews.com |
Cartridge loading - does it matter?
"Don Pearce" wrote The question of transformers for mc carts is interesting. A transformer will multiply the capacitance as it divides the resistance, so it needs to go at the amplifier end of the cable, not the cartridge end if many nanofarads aren't to be dropped across the cartridge. Again, interesting to know - but I bet it's near enough impossible to tell.... Maybe.... more sums for me later. d As I sort of suspected. Adding the transformer makes the mc more susceptible to capacitance following the transformer, but not preceding it. Again, I would query how *hearable* this might be...?? FWIW, my stepup amp/transformers usually go on the end of the TT lead when I user a low o/p cart and the distance to the amp will vary according to what kit is in play at the time...?? |
Cartridge loading - does it matter?
"Keith G" wrote in message ... "Don Pearce" wrote The question of transformers for mc carts is interesting. A transformer will multiply the capacitance as it divides the resistance, so it needs to go at the amplifier end of the cable, not the cartridge end if many nanofarads aren't to be dropped across the cartridge. Again, interesting to know - but I bet it's near enough impossible to tell.... Maybe.... more sums for me later. d As I sort of suspected. Adding the transformer makes the mc more susceptible to capacitance following the transformer, but not preceding it. Again, I would query how *hearable* this might be...?? FWIW, my stepup amp/transformers usually go on the end of the TT lead when I user a low o/p cart and the distance to the amp will vary according to what kit is in play at the time...?? 'user'....??? (Bad case of Phonetic Phingers tonight....!! :-) |
Cartridge loading - does it matter?
On Sun, 15 Oct 2006 19:18:12 +0100, "Keith G"
wrote: "Keith G" wrote in message .. . "Don Pearce" wrote The question of transformers for mc carts is interesting. A transformer will multiply the capacitance as it divides the resistance, so it needs to go at the amplifier end of the cable, not the cartridge end if many nanofarads aren't to be dropped across the cartridge. Again, interesting to know - but I bet it's near enough impossible to tell.... Maybe.... more sums for me later. d As I sort of suspected. Adding the transformer makes the mc more susceptible to capacitance following the transformer, but not preceding it. Again, I would query how *hearable* this might be...?? FWIW, my stepup amp/transformers usually go on the end of the TT lead when I user a low o/p cart and the distance to the amp will vary according to what kit is in play at the time...?? 'user'....??? (Bad case of Phonetic Phingers tonight....!! :-) Ah well. The whole thing is so sensitive to actual values that I'd have to get into detail to work that out. It is all going on right at the top, in any case, so probably wouldn't be hugely intrusive. d -- Pearce Consulting http://www.pearce.uk.com -- Posted via a free Usenet account from http://www.teranews.com |
Cartridge loading - does it matter?
"Don Pearce" wrote in message ... On Sun, 15 Oct 2006 19:18:12 +0100, "Keith G" wrote: "Keith G" wrote in message . .. "Don Pearce" wrote The question of transformers for mc carts is interesting. A transformer will multiply the capacitance as it divides the resistance, so it needs to go at the amplifier end of the cable, not the cartridge end if many nanofarads aren't to be dropped across the cartridge. Again, interesting to know - but I bet it's near enough impossible to tell.... Maybe.... more sums for me later. d As I sort of suspected. Adding the transformer makes the mc more susceptible to capacitance following the transformer, but not preceding it. Again, I would query how *hearable* this might be...?? FWIW, my stepup amp/transformers usually go on the end of the TT lead when I user a low o/p cart and the distance to the amp will vary according to what kit is in play at the time...?? 'user'....??? (Bad case of Phonetic Phingers tonight....!! :-) Ah well. The whole thing is so sensitive to actual values that I'd have to get into detail to work that out. It is all going on right at the top, in any case, so probably wouldn't be hugely intrusive. OK - nothing to worry a *Lowther User* then...?? :-) |
Cartridge loading - does it matter?
In article , Don Pearce
wrote: A quick google on mc cartridge inductance yielded a small crop. An Audio technica gave 70uH in series with 17 ohms, and a load of 20 ohms or more. Another, the Eroica, is 12uH with 8 ohms so there is quite a variation. As you say, the inductance tends to go hand in hand with output level. I have made the same search for mm cartridges, and come up with typical values around 500mH. The interesting thing (for me) in the above is that the MC inductances are over a thousand times lower than is typical for a MM. Yet the output levels tend to only be of the order of a tenth to a hundredth of an MM. A x20 step-up TX would convert the above MC values into 28 mH and 4.8mH, which are both pretty small values. The source resistances do rise, though, to 8k and 3k2. My model was simple - a voltage source in series with the L and C, and a load resistor in parallel with the cable capacitance. Again I looked around the various arm assemblies to find typical values, as well as the recommended values. As I say, what I found was that you can take huge liberties with the loading of mc cartridges and the only effect is on the level. The same is not so for mm cartridges, which appear highly resonant with cable capacity at the top end. Yes. That makes sense, and your figures support the magazines tending to ignore this - yet then raises the puzzle of why loading should be regarded as having any effect at all... and also Nick's curious results. Maybe this is a non-issue with 'low output' (i.e. tiny coil) MCs, but becomes one with 'high output' MCs as they have much bigger coils. The question of transformers for mc carts is interesting. A transformer will multiply the capacitance as it divides the resistance, so it needs to go at the amplifier end of the cable, not the cartridge end if many nanofarads aren't to be dropped across the cartridge. Would also need to be cautious of RIAA MM amps where the designer has already deliberately added some capacitance to get a decent loading for the common MM designs. 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?
Don Pearce wrote:
On Sun, 15 Oct 2006 15:19:41 +0100, "Keith G" wrote: "Don Pearce" wrote As I say, what I found was that you can take huge liberties with the loading of mc cartridges and the only effect is on the level. Been waiting for that to show - it's all I know about the subject....!! :-) The question of transformers for mc carts is interesting. A transformer will multiply the capacitance as it divides the resistance, so it needs to go at the amplifier end of the cable, not the cartridge end if many nanofarads aren't to be dropped across the cartridge. Again, interesting to know - but I bet it's near enough impossible to tell.... Maybe.... more sums for me later. d It's interesting that the famed Ortofon SPU cartridge had a transformer in the headshell, (which accounted for a lot of its excessive weight). and therefore saw the capacitance of the arm cable. I came across a US patent No 4035737 of 12th July 1977 from John J Curl with an electronic moving coil step-up which, if I read the circuit correctly, had a virtual earth input, and thus loaded the cartridge with essentially zero ohms, using the cartridge's current output. The patent claims extremely low noise through the use of multiple parallel pairs of transistors, and very low distortion through the use of push-pull pairs. Although the distortion of the electronics may be low, I wonder about that of the cartridge driving into a short-circuit. When I get some time in the next couple of weeks, I'll try and build the circuit and see what it does. S. |
Cartridge loading - does it matter?
On Mon, 16 Oct 2006 10:22:55 +0100, Serge Auckland
wrote: Don Pearce wrote: On Sun, 15 Oct 2006 15:19:41 +0100, "Keith G" wrote: "Don Pearce" wrote As I say, what I found was that you can take huge liberties with the loading of mc cartridges and the only effect is on the level. Been waiting for that to show - it's all I know about the subject....!! :-) The question of transformers for mc carts is interesting. A transformer will multiply the capacitance as it divides the resistance, so it needs to go at the amplifier end of the cable, not the cartridge end if many nanofarads aren't to be dropped across the cartridge. Again, interesting to know - but I bet it's near enough impossible to tell.... Maybe.... more sums for me later. d It's interesting that the famed Ortofon SPU cartridge had a transformer in the headshell, (which accounted for a lot of its excessive weight). and therefore saw the capacitance of the arm cable. I came across a US patent No 4035737 of 12th July 1977 from John J Curl with an electronic moving coil step-up which, if I read the circuit correctly, had a virtual earth input, and thus loaded the cartridge with essentially zero ohms, using the cartridge's current output. The patent claims extremely low noise through the use of multiple parallel pairs of transistors, and very low distortion through the use of push-pull pairs. Although the distortion of the electronics may be low, I wonder about that of the cartridge driving into a short-circuit. When I get some time in the next couple of weeks, I'll try and build the circuit and see what it does. S. I remember that cartridge. Back in the early seventies I was given an SPU-TE. I had to modify my arm to fit it, but eventually got it in. I put a record on and it played the first track just fine. Suddenly it jumped inwards and there was a loud grinding sound. I had a ten inch steel turntable, and the leakage magnetism from the cart was so strong that when it was close enough it sucked itself hard down onto the turntable, wrecking the cantilever. Given that leakage field, I'm surprised that the transformer even worked, and was not saturated to death. As for current drive vs. voltage drive - they are as good as each other, and to suggest that it is driving a short circuit is simply a voltage-centric view of what amounts to a quite normal current connection. d -- Pearce Consulting http://www.pearce.uk.com -- Posted via a free Usenet account from http://www.teranews.com |
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