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#1
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Phono Input Capacitance question
I'm using a Luxman C-1010 preamp with a variety of
Stanton/Pickering phono cartridges. The capacitance load requirement for all of these cartridges is 275 pf. Luxman didn't specify the capacitance of their input circuit. That's what I need to know. I have a capacitor test meter, so I can measure the capacitance of all cabling; the meter goes bonkers on input circuits. I need to come up with a quick and dirty way to determine the capacitance of the preamp (or an actual figure!). I'd appreciate any help, especially help that's accurate. Thanks. Richard |
#2
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Phono Input Capacitance question
"Richard Steinfeld" wrote in message ... I'm using a Luxman C-1010 preamp with a variety of Stanton/Pickering phono cartridges. The capacitance load requirement for all of these cartridges is 275 pf. Luxman didn't specify the capacitance of their input circuit. That's what I need to know. I have a capacitor test meter, so I can measure the capacitance of all cabling; the meter goes bonkers on input circuits. I need to come up with a quick and dirty way to determine the capacitance of the preamp (or an actual figure!). I'd appreciate any help, especially help that's accurate. You're going about it the wrong way. The 275pF figure may not be exact for your cartridge anyway, so an accurate measurement may make you feel good, but not necessarily give you flattest response.. Get a good test record and adjust the input capacitance for flattest high frequency response. TonyP. |
#3
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Phono Input Capacitance question
"Richard Steinfeld" wrote in message ... I'm using a Luxman C-1010 preamp with a variety of Stanton/Pickering phono cartridges. The capacitance load requirement for all of these cartridges is 275 pf. Luxman didn't specify the capacitance of their input circuit. That's what I need to know. I have a capacitor test meter, so I can measure the capacitance of all cabling; the meter goes bonkers on input circuits. I need to come up with a quick and dirty way to determine the capacitance of the preamp (or an actual figure!). I'd appreciate any help, especially help that's accurate. You're going about it the wrong way. The 275pF figure may not be exact for your cartridge anyway, so an accurate measurement may make you feel good, but not necessarily give you flattest response.. Get a good test record and adjust the input capacitance for flattest high frequency response. TonyP. |
#4
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Phono Input Capacitance question
"Richard Steinfeld" wrote in message ... I'm using a Luxman C-1010 preamp with a variety of Stanton/Pickering phono cartridges. The capacitance load requirement for all of these cartridges is 275 pf. Luxman didn't specify the capacitance of their input circuit. That's what I need to know. I have a capacitor test meter, so I can measure the capacitance of all cabling; the meter goes bonkers on input circuits. I need to come up with a quick and dirty way to determine the capacitance of the preamp (or an actual figure!). I'd appreciate any help, especially help that's accurate. You're going about it the wrong way. The 275pF figure may not be exact for your cartridge anyway, so an accurate measurement may make you feel good, but not necessarily give you flattest response.. Get a good test record and adjust the input capacitance for flattest high frequency response. TonyP. |
#5
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Phono Input Capacitance question
TonyP wrote:
"Richard Steinfeld" wrote in message ... I'm using a Luxman C-1010 preamp with a variety of Stanton/Pickering phono cartridges. The capacitance load requirement for all of these cartridges is 275 pf. Luxman didn't specify the capacitance of their input circuit. That's what I need to know. I have a capacitor test meter, so I can measure the capacitance of all cabling; the meter goes bonkers on input circuits. I need to come up with a quick and dirty way to determine the capacitance of the preamp (or an actual figure!). I'd appreciate any help, especially help that's accurate. You're going about it the wrong way. The 275pF figure may not be exact for your cartridge anyway, so an accurate measurement may make you feel good, but not necessarily give you flattest response.. Get a good test record and adjust the input capacitance for flattest high frequency response. TonyP. Flattest? Or closest to the RIAA curve? Where are you suggesting he measure? -- The e-mail address in our reply-to line is reversed in an attempt to minimize spam. Our true address is of the form . |
#6
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Phono Input Capacitance question
TonyP wrote:
"Richard Steinfeld" wrote in message ... I'm using a Luxman C-1010 preamp with a variety of Stanton/Pickering phono cartridges. The capacitance load requirement for all of these cartridges is 275 pf. Luxman didn't specify the capacitance of their input circuit. That's what I need to know. I have a capacitor test meter, so I can measure the capacitance of all cabling; the meter goes bonkers on input circuits. I need to come up with a quick and dirty way to determine the capacitance of the preamp (or an actual figure!). I'd appreciate any help, especially help that's accurate. You're going about it the wrong way. The 275pF figure may not be exact for your cartridge anyway, so an accurate measurement may make you feel good, but not necessarily give you flattest response.. Get a good test record and adjust the input capacitance for flattest high frequency response. TonyP. Flattest? Or closest to the RIAA curve? Where are you suggesting he measure? -- The e-mail address in our reply-to line is reversed in an attempt to minimize spam. Our true address is of the form . |
#7
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Phono Input Capacitance question
TonyP wrote:
"Richard Steinfeld" wrote in message ... I'm using a Luxman C-1010 preamp with a variety of Stanton/Pickering phono cartridges. The capacitance load requirement for all of these cartridges is 275 pf. Luxman didn't specify the capacitance of their input circuit. That's what I need to know. I have a capacitor test meter, so I can measure the capacitance of all cabling; the meter goes bonkers on input circuits. I need to come up with a quick and dirty way to determine the capacitance of the preamp (or an actual figure!). I'd appreciate any help, especially help that's accurate. You're going about it the wrong way. The 275pF figure may not be exact for your cartridge anyway, so an accurate measurement may make you feel good, but not necessarily give you flattest response.. Get a good test record and adjust the input capacitance for flattest high frequency response. TonyP. Flattest? Or closest to the RIAA curve? Where are you suggesting he measure? -- The e-mail address in our reply-to line is reversed in an attempt to minimize spam. Our true address is of the form . |
#8
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Phono Input Capacitance question
In , on 06/27/04
at 08:45 PM, "Richard Steinfeld" said: I'm using a Luxman C-1010 preamp with a variety of Stanton/Pickering phono cartridges. The capacitance load requirement for all of these cartridges is 275 pf. Luxman didn't specify the capacitance of their input circuit. That's what I need to know. I have a capacitor test meter, so I can measure the capacitance of all cabling; the meter goes bonkers on input circuits. I need to come up with a quick and dirty way to determine the capacitance of the preamp (or an actual figure!). I'd appreciate any help, especially help that's accurate. Generally, the electronic manufacturers expect cartridges need loading in this range and design their inputs accordingly. (Unfortunately, they must guess the turntable wiring capacitance.) I assume that the C-1010's active components in the input circuit are frustrating the capacitance meter. Try using the lowest test voltage that you can. If you don't mind fussing with things, break the connection between the input jack as physically close to the first active device as you can. There will probably be a difference between measuring while the C-1010 is turned on or off, but in general, I feel that the test voltage will be a bit high and you'll bump into some nonlinearity either way. There are many methods that could be used to measure capacitance. Pick one that measures at less than 0.5 volts pp otherwise you could run into an active component inside the preamp that turns on. One method that you may be able to manage is to insert a known capacitor in series with the tester. This may reduce the voltage enough to avoid the nonlinearity in the preamp and block any DC component from the tester. Another technique would be to inject a known single frequency into the preamp through a resistor and measure the voltage at the RCA jack. Then start adding parallel capacitors until the voltage falls to 50 percent of the original. Be careful to use a low signal voltage. Don't forget to deal with the input capacitance of the voltage measuring device and your tester. --- Others have suggested measuring the frequency response of the system using a test record and tune the result for a flat response. This sounds like a good idea, but I think you will find enough variation in different test records to frustrate your sense of accuracy. Also, be very careful to duplicate the temperature during all test runs, then operate your turntable at that temperature. Finally, cartridges, typically, are not very flat. There are peaks, dips, and resonances. You may have to scratch your head a bit to decide when things are "flat". As you measure the frequency response, keep the response of your measuring device in mind. Most DVM's are not flat enough for audio work. --- I think your easiest path is to examine the preamp's input circuit. You may find series and/or parallel capacitors in front of the first active device. Calculate the equivalent capacitance of that network and add a few pF for the wiring. ----------------------------------------------------------- spam: wordgame:123(abc):14 9 20 5 2 9 18 4 at 22 15 9 3 5 14 5 20 dot 3 15 13 (Barry Mann) [sorry about the puzzle, spammers are ruining my mailbox] ----------------------------------------------------------- |
#9
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Phono Input Capacitance question
In , on 06/27/04
at 08:45 PM, "Richard Steinfeld" said: I'm using a Luxman C-1010 preamp with a variety of Stanton/Pickering phono cartridges. The capacitance load requirement for all of these cartridges is 275 pf. Luxman didn't specify the capacitance of their input circuit. That's what I need to know. I have a capacitor test meter, so I can measure the capacitance of all cabling; the meter goes bonkers on input circuits. I need to come up with a quick and dirty way to determine the capacitance of the preamp (or an actual figure!). I'd appreciate any help, especially help that's accurate. Generally, the electronic manufacturers expect cartridges need loading in this range and design their inputs accordingly. (Unfortunately, they must guess the turntable wiring capacitance.) I assume that the C-1010's active components in the input circuit are frustrating the capacitance meter. Try using the lowest test voltage that you can. If you don't mind fussing with things, break the connection between the input jack as physically close to the first active device as you can. There will probably be a difference between measuring while the C-1010 is turned on or off, but in general, I feel that the test voltage will be a bit high and you'll bump into some nonlinearity either way. There are many methods that could be used to measure capacitance. Pick one that measures at less than 0.5 volts pp otherwise you could run into an active component inside the preamp that turns on. One method that you may be able to manage is to insert a known capacitor in series with the tester. This may reduce the voltage enough to avoid the nonlinearity in the preamp and block any DC component from the tester. Another technique would be to inject a known single frequency into the preamp through a resistor and measure the voltage at the RCA jack. Then start adding parallel capacitors until the voltage falls to 50 percent of the original. Be careful to use a low signal voltage. Don't forget to deal with the input capacitance of the voltage measuring device and your tester. --- Others have suggested measuring the frequency response of the system using a test record and tune the result for a flat response. This sounds like a good idea, but I think you will find enough variation in different test records to frustrate your sense of accuracy. Also, be very careful to duplicate the temperature during all test runs, then operate your turntable at that temperature. Finally, cartridges, typically, are not very flat. There are peaks, dips, and resonances. You may have to scratch your head a bit to decide when things are "flat". As you measure the frequency response, keep the response of your measuring device in mind. Most DVM's are not flat enough for audio work. --- I think your easiest path is to examine the preamp's input circuit. You may find series and/or parallel capacitors in front of the first active device. Calculate the equivalent capacitance of that network and add a few pF for the wiring. ----------------------------------------------------------- spam: wordgame:123(abc):14 9 20 5 2 9 18 4 at 22 15 9 3 5 14 5 20 dot 3 15 13 (Barry Mann) [sorry about the puzzle, spammers are ruining my mailbox] ----------------------------------------------------------- |
#10
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Phono Input Capacitance question
In , on 06/27/04
at 08:45 PM, "Richard Steinfeld" said: I'm using a Luxman C-1010 preamp with a variety of Stanton/Pickering phono cartridges. The capacitance load requirement for all of these cartridges is 275 pf. Luxman didn't specify the capacitance of their input circuit. That's what I need to know. I have a capacitor test meter, so I can measure the capacitance of all cabling; the meter goes bonkers on input circuits. I need to come up with a quick and dirty way to determine the capacitance of the preamp (or an actual figure!). I'd appreciate any help, especially help that's accurate. Generally, the electronic manufacturers expect cartridges need loading in this range and design their inputs accordingly. (Unfortunately, they must guess the turntable wiring capacitance.) I assume that the C-1010's active components in the input circuit are frustrating the capacitance meter. Try using the lowest test voltage that you can. If you don't mind fussing with things, break the connection between the input jack as physically close to the first active device as you can. There will probably be a difference between measuring while the C-1010 is turned on or off, but in general, I feel that the test voltage will be a bit high and you'll bump into some nonlinearity either way. There are many methods that could be used to measure capacitance. Pick one that measures at less than 0.5 volts pp otherwise you could run into an active component inside the preamp that turns on. One method that you may be able to manage is to insert a known capacitor in series with the tester. This may reduce the voltage enough to avoid the nonlinearity in the preamp and block any DC component from the tester. Another technique would be to inject a known single frequency into the preamp through a resistor and measure the voltage at the RCA jack. Then start adding parallel capacitors until the voltage falls to 50 percent of the original. Be careful to use a low signal voltage. Don't forget to deal with the input capacitance of the voltage measuring device and your tester. --- Others have suggested measuring the frequency response of the system using a test record and tune the result for a flat response. This sounds like a good idea, but I think you will find enough variation in different test records to frustrate your sense of accuracy. Also, be very careful to duplicate the temperature during all test runs, then operate your turntable at that temperature. Finally, cartridges, typically, are not very flat. There are peaks, dips, and resonances. You may have to scratch your head a bit to decide when things are "flat". As you measure the frequency response, keep the response of your measuring device in mind. Most DVM's are not flat enough for audio work. --- I think your easiest path is to examine the preamp's input circuit. You may find series and/or parallel capacitors in front of the first active device. Calculate the equivalent capacitance of that network and add a few pF for the wiring. ----------------------------------------------------------- spam: wordgame:123(abc):14 9 20 5 2 9 18 4 at 22 15 9 3 5 14 5 20 dot 3 15 13 (Barry Mann) [sorry about the puzzle, spammers are ruining my mailbox] ----------------------------------------------------------- |
#11
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Phono Input Capacitance question
"CJT" wrote in message
TonyP wrote: You're going about it the wrong way. The 275pF figure may not be exact for your cartridge anyway, so an accurate measurement may make you feel good, but not necessarily give you flattest response.. Get a good test record and adjust the input capacitance for flattest high frequency response. Agreed. Flattest? Or closest to the RIAA curve? Where are you suggesting he measure? Test records are generally made with RIAA pre-emphais, so your goal is flattest possible response via the output of a RIAA equalized preamp. The High Fidelity News test record is arguably the best contemporary test record. However, many audiophiles bought test records in the past and never seriously used them. So, there are quite a number of the classic test records of the past (example CBS labs and Stereo Review) in good shape, available on eBay and the like. |
#12
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Phono Input Capacitance question
"CJT" wrote in message
TonyP wrote: You're going about it the wrong way. The 275pF figure may not be exact for your cartridge anyway, so an accurate measurement may make you feel good, but not necessarily give you flattest response.. Get a good test record and adjust the input capacitance for flattest high frequency response. Agreed. Flattest? Or closest to the RIAA curve? Where are you suggesting he measure? Test records are generally made with RIAA pre-emphais, so your goal is flattest possible response via the output of a RIAA equalized preamp. The High Fidelity News test record is arguably the best contemporary test record. However, many audiophiles bought test records in the past and never seriously used them. So, there are quite a number of the classic test records of the past (example CBS labs and Stereo Review) in good shape, available on eBay and the like. |
#13
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Phono Input Capacitance question
"CJT" wrote in message
TonyP wrote: You're going about it the wrong way. The 275pF figure may not be exact for your cartridge anyway, so an accurate measurement may make you feel good, but not necessarily give you flattest response.. Get a good test record and adjust the input capacitance for flattest high frequency response. Agreed. Flattest? Or closest to the RIAA curve? Where are you suggesting he measure? Test records are generally made with RIAA pre-emphais, so your goal is flattest possible response via the output of a RIAA equalized preamp. The High Fidelity News test record is arguably the best contemporary test record. However, many audiophiles bought test records in the past and never seriously used them. So, there are quite a number of the classic test records of the past (example CBS labs and Stereo Review) in good shape, available on eBay and the like. |
#14
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Phono Input Capacitance question
"Barry Mann" wrote in message
om As you measure the frequency response, keep the response of your measuring device in mind. Most DVM's are not flat enough for audio work. Agreed. DVM's tend to break down into two categories w/r/t frequency response. Many are basically designed for measuring power line voltages, and have pretty fair response up to about 1 KHz. Their response then drops like a stone. Others are designed to have good frequency response. I have a Fluke 85, and it is within 0.5 dB or better over the audio band. I have a Protek 506, and its within about 0.5 dB up to 20 KHz. Arguably, the best way to measure the frequency response of a vinyl playback system is to use a good computer sound card. hooked to the output of your phono preamp, or stand-alone component preamp. Record the playback of a test record and then analyze it. You can confirm the performance of your sound card using a freebie download called "RightMark Audio Analyzer" The frequency response range affected by capacitive loading is 500 Hz. You can get more consistent measurements if you filter out noise and garbage below 500 Hz, which some DAW software like CoolEdit and Goldwave support. They also have analytical features that will enable you to make accurate measurements of selections in a file. |
#15
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Phono Input Capacitance question
"Barry Mann" wrote in message
om As you measure the frequency response, keep the response of your measuring device in mind. Most DVM's are not flat enough for audio work. Agreed. DVM's tend to break down into two categories w/r/t frequency response. Many are basically designed for measuring power line voltages, and have pretty fair response up to about 1 KHz. Their response then drops like a stone. Others are designed to have good frequency response. I have a Fluke 85, and it is within 0.5 dB or better over the audio band. I have a Protek 506, and its within about 0.5 dB up to 20 KHz. Arguably, the best way to measure the frequency response of a vinyl playback system is to use a good computer sound card. hooked to the output of your phono preamp, or stand-alone component preamp. Record the playback of a test record and then analyze it. You can confirm the performance of your sound card using a freebie download called "RightMark Audio Analyzer" The frequency response range affected by capacitive loading is 500 Hz. You can get more consistent measurements if you filter out noise and garbage below 500 Hz, which some DAW software like CoolEdit and Goldwave support. They also have analytical features that will enable you to make accurate measurements of selections in a file. |
#16
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Phono Input Capacitance question
"Barry Mann" wrote in message
om As you measure the frequency response, keep the response of your measuring device in mind. Most DVM's are not flat enough for audio work. Agreed. DVM's tend to break down into two categories w/r/t frequency response. Many are basically designed for measuring power line voltages, and have pretty fair response up to about 1 KHz. Their response then drops like a stone. Others are designed to have good frequency response. I have a Fluke 85, and it is within 0.5 dB or better over the audio band. I have a Protek 506, and its within about 0.5 dB up to 20 KHz. Arguably, the best way to measure the frequency response of a vinyl playback system is to use a good computer sound card. hooked to the output of your phono preamp, or stand-alone component preamp. Record the playback of a test record and then analyze it. You can confirm the performance of your sound card using a freebie download called "RightMark Audio Analyzer" The frequency response range affected by capacitive loading is 500 Hz. You can get more consistent measurements if you filter out noise and garbage below 500 Hz, which some DAW software like CoolEdit and Goldwave support. They also have analytical features that will enable you to make accurate measurements of selections in a file. |
#17
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Phono Input Capacitance question
"Barry Mann" wrote in message om... Others have suggested measuring the frequency response of the system using a test record and tune the result for a flat response. This sounds like a good idea, but I think you will find enough variation in different test records to frustrate your sense of accuracy. I think you will find most test records are better than anything else you are likely to play on the turntable, so it hardly matters IMO. Vinyl is simply not a high accuracy source to begin with. What you seem to be saying is that the measurements should be much more accurate than the records. Why? (other than feel good factor) Also, be very careful to duplicate the temperature during all test runs, then operate your turntable at that temperature. This is also a trifle obsessive, but sure, the measurements should be made at 20 - 23degC. Finally, cartridges, typically, are not very flat. There are peaks, dips, and resonances. You may have to scratch your head a bit to decide when things are "flat". A good cartridge will not have serious peaks dips or resonances in the 20-20kHz band. If it does, get a new one :-) The two main resonaces should occur below 20Hz and above 20 kHz. As you measure the frequency response, keep the response of your measuring device in mind. Most DVM's are not flat enough for audio work. Usually the case, but easy to check. TonyP. |
#18
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Phono Input Capacitance question
"Barry Mann" wrote in message om... Others have suggested measuring the frequency response of the system using a test record and tune the result for a flat response. This sounds like a good idea, but I think you will find enough variation in different test records to frustrate your sense of accuracy. I think you will find most test records are better than anything else you are likely to play on the turntable, so it hardly matters IMO. Vinyl is simply not a high accuracy source to begin with. What you seem to be saying is that the measurements should be much more accurate than the records. Why? (other than feel good factor) Also, be very careful to duplicate the temperature during all test runs, then operate your turntable at that temperature. This is also a trifle obsessive, but sure, the measurements should be made at 20 - 23degC. Finally, cartridges, typically, are not very flat. There are peaks, dips, and resonances. You may have to scratch your head a bit to decide when things are "flat". A good cartridge will not have serious peaks dips or resonances in the 20-20kHz band. If it does, get a new one :-) The two main resonaces should occur below 20Hz and above 20 kHz. As you measure the frequency response, keep the response of your measuring device in mind. Most DVM's are not flat enough for audio work. Usually the case, but easy to check. TonyP. |
#19
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Phono Input Capacitance question
"Barry Mann" wrote in message om... Others have suggested measuring the frequency response of the system using a test record and tune the result for a flat response. This sounds like a good idea, but I think you will find enough variation in different test records to frustrate your sense of accuracy. I think you will find most test records are better than anything else you are likely to play on the turntable, so it hardly matters IMO. Vinyl is simply not a high accuracy source to begin with. What you seem to be saying is that the measurements should be much more accurate than the records. Why? (other than feel good factor) Also, be very careful to duplicate the temperature during all test runs, then operate your turntable at that temperature. This is also a trifle obsessive, but sure, the measurements should be made at 20 - 23degC. Finally, cartridges, typically, are not very flat. There are peaks, dips, and resonances. You may have to scratch your head a bit to decide when things are "flat". A good cartridge will not have serious peaks dips or resonances in the 20-20kHz band. If it does, get a new one :-) The two main resonaces should occur below 20Hz and above 20 kHz. As you measure the frequency response, keep the response of your measuring device in mind. Most DVM's are not flat enough for audio work. Usually the case, but easy to check. TonyP. |
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