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paulsmith048j wrote:
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Accession MM Capacitance/Loading Settings |
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paulsmith048j 
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 Topic: Accession MM Capacitance/Loading SettingsPosted: 01 Feb 2022 at 7:14pm |
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Good evening everyone,
I am expecting delivery of a brand new Graham Slee Accession MM phono stage tomorrow :-) I have a pretty `high end ` LP12/Naim system which is mainly used for vinyl replay. My tonearm is an Audio Origami PU7, and its creator Johnnie (`J7`) has informed me that the total capacitance loading contributed by the tonearm wiring and the 1 metre long phono cable which will be connected to the input of the Accession is 110 pf. I plan to use 0.6m Cusat50 RCA-RCA cable to connect the output from the Accession to one of the line inputs of my Naim Nait XS3 integrated amplifier. The quoted capacitance of 0.6m of Cusat50 is (55 x 0.6 =) 33 pf. So, the total loading so far caused by all the cables/interconnects is approx` 143 pf. My cartridge is the Audio Technica 760 SLC and from its advertised specifications, it ideally wants to see a total capacitance of between 100 and 200 pf. I am aware of the dip switches on the rear of the accession which from L to R give 100/220/220/100 pf for the left/right channel. I assume that if I choose which switches are in the ON position I can choose loading values of 100/220/320 pf? However, all 3 of those options would give me a total loading seen by the cartridge of over 240 pf. Am I correct in thinking that if ALL FOUR dip switches are left in the OFF position then the Accession will contributing `ZERO capacitance` therefore leaving me at 143 pf which `might` be the sweet-spot for my cartridge? I obviously intend to experiment with different loading options and will let my ears ultimately decide the best setting :-) Any advice/opinions from the experts will be most welcome. |
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Fatmangolf
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Posted: 01 Feb 2022 at 8:36pm |
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Hello Paul. First the good news you need only consider the PU7's leads with 110pF as that is 'seen' by your cartridge and the other 0.6m cable is not. So you could set the Accession on 0pF added capacitance and see how things sound with 110pF loading, close to the bottom end of AT's recomemned loading range. You have the option of adding more capacitance with the Accession on 100pF. The resulting 210pF is close enough to the top end of AT's recommended range so please try that too. By all means try the 220pF setting to get 330pF. Please go with the option that sounds best to you. |
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Jon
Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC. |
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Graham Slee
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Posted: 01 Feb 2022 at 8:44pm |
Wrong. The 33pf is between the Accession and your amp and is nothing to do with what the cartridge "sees" You will have the 110pf stated by J7, and you can either have all switches off, or the 100pf switches on. Even with the 100pf switch selected it will be 210pf and I assure you you'd be hard pressed to notice between 200pf and 210pf. Thank you for choosing our Accession M. Graham Jon, you pipped me by 8 minutes! Edited by Graham Slee - 01 Feb 2022 at 8:45pm |
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paulsmith048j
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Posted: 01 Feb 2022 at 9:55pm |
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Many thanks Graham and Jon for your responses.
I really did think that the capacitance rating of the Cusat50 interconnect linking the Accession MM and my Naim amplifier was relevant. Thank-you for pointing out my error. I will shortly be 60 years old and have no doubt lost a fair bit of HF hearing above approx` 10Khz compared to my younger days, so I`ll try the 0pf and 100pf options on the Accession and see what setting sounds best to my ears. I guess that means I `ll be switching between a total of approx` 110pf and 210pf. I assume the higher setting of 210pf will move the treble `peak` to a lower frequency of, say, approx` 12Khz and the 110pf option will move the peak to a higher frequency - say about 16Khz but with a more gentle roll-off above that? Whether my 60 year old ears will detect a difference remains to be seen. Oh to be 30 years old again :-)
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Graham Slee
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Posted: 01 Feb 2022 at 10:31pm |
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How to work it out... Given the cartridge inductance of 480mH From fR = 1/2pi.sqrtLC L = 0.48H, C = 0.00000000021F (210pf) = 1/2pi.sqrt 0.48 x 0.00000000021 = 1/2pi.0.00001004 = 1/0.0000631 = 15.852kHz L = 0.48H, C = 0.00000000011F (110pf) = 1/2pi.sqrt 0.48 x 0.00000000011 = 1/2pi.0.000007266 = 1/0.00004566 = 21.902kHz
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That none should be able to buy or sell without a smartphone and the knowledge in how to use apps
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paulsmith048j
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Posted: 02 Feb 2022 at 7:16am |
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Many thanks for that Graham,
I wasn`t a million miles out with my clumsy `guess` then  Given that I`m probably hearing very little above 15 kHz at my age, there probably will be very little to choose between the 2 settings. How would the 2 different frequency response graphs compare in terms of any initial flatness/neutrality and the rate of roll-off after the treble peaks? Kind regards, Paul
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paulsmith048j
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Posted: 02 Feb 2022 at 8:42am |
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[QUOTE=Graham Slee]
How to work it out... Given the cartridge inductance of 480mH Hello again Graham, I am reliably informed that the cartridge inductance on my AT760SLC is actually 460mH. What would your formula give as a result with that modified value please?
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