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Capacitance |
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Paul H
Senior Member Joined: 13 Mar 2016 Location: Nottingham Status: Offline Points: 121 |
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Posted: 16 Mar 2016 at 9:05am |
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I'm looking for a little advice. I've been on a steep learning curve with regards to vinyl set up and have been learning about the joys of capacitance and how it affects one's set up. My system is a hodge podge of bits and pieces bought over the years at a time when I was blissfully ignorant of what I was buying. For example, I have no idea of the capacitance of my current amp nor that of the tonearm wiring. I replaced the cable between table and amp to Blue Jeans LC-1 partly because it comes highly recommended and partly because I know it to have a low capacitance.
However, my rough and ready calculations suggest that I'm still generating anywhere between 160 and 280 pF of capacitance (this assumes my tonearm has roughly 25 pF and my amp has either 100 or 220 pF). As I understand it, capacitance creates a "hump" in the frequency response at certain frequencies followed by a sharp drop off and the calculations above suggest that in my system this occurs at either 15kHz or 11kHz. I suspect that my amp has a cap rating of 220pF and comparing needledrops played back through my pc with the actual records, I notice a very definite drop in volume at frequencies where I'd expect to hear percussion (think of Ringo's thrashing around on early Beatles albums). This can be corrected (although not sounding good) by adjusting my treble, which is set at 10kHz. If my assumptions are correct, this drop in volume is, at least in part, a result of having too much capacitance in my system. I wonder whether anyone has any thoughts on this. I'd particularly welcome any comments about the impact a lower capacitance amp would have. Is it likely to remove this fall off in volume? Frankly, it's driving me nuts because its making my vinyl sound much darker than it ought to.
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ProJect 1Xpression Carbon UKX w/ Ortofon 2M Black; Arcam Alpha 7 CD player; Graham Slee Revelation M pre; Denon PMA 355UK amp; Epos K1 speakers; Blue Jeans LC-1 interconnects. Room: 2.9m x 3.1m.
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Drewan77
Senior Member Joined: 25 May 2013 Location: Chester,England Status: Offline Points: 1544 |
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Hi Paul
Treble tone controls can have strange effects, especially if the 10khz frequency and its bandwidth do not correspond to the capacitance issue you may have. I suspect this is mostly to do with the phono stage in the Denon PMA 355UK because the 2M Blue itself is 'neutral, bordering on bright' and you are using a lower capacitance interconnect. On another thread, several of us recommended listening to the Era Gold V or Reflex M via the loan scheme. I am confident that either would solve this issue or if you want to play around with capacitive loading, go the whole hog and borrow an Accession too - it will put your mind at rest! I had tried out its' different settings on several cartridges including the Ortofon 2M Black (with a Blue stylus) - the 100pf setting sounded the most natural vs 220pf & 330pf.
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............................. Andrew |
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Paul H
Senior Member Joined: 13 Mar 2016 Location: Nottingham Status: Offline Points: 121 |
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Hi Andrew, Yes, possibly. I've PM'd fatmangolf to arrange a loan of the Era Gold V.
I'd love to borrow the Accession but it's waaayyy above my budget and difficult to justify given the limitations of my room and overall system. I'm afraid that if I audition it I'll want it...
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ProJect 1Xpression Carbon UKX w/ Ortofon 2M Black; Arcam Alpha 7 CD player; Graham Slee Revelation M pre; Denon PMA 355UK amp; Epos K1 speakers; Blue Jeans LC-1 interconnects. Room: 2.9m x 3.1m.
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Graham Slee
Admin Group Retired Joined: 11 Jan 2008 Location: South Yorkshire Status: Offline Points: 16298 |
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Without capacitive loading moving magnet cartridges would be in a sorry state...
Capacitive loading with the addition of a damping resistor (47k usually) enables them to extend almost flat (electrically) to around 16kHz, after which their output will fall at the rate of 12dB/octave. "Tuning fork" techniques are used to mechanically extend the frequency response beyond the electrical frequency response. MM inductance centres on 0.5H ('alf an 'enry), and with 200pf (or as they used to write: 200uuF) the formula f = 1/2pi.(sqrt L x C) where f = frequency; L = inductance; and C = capacitance - gives the resonant frequency of 15,915.49431Hz. Close enough to 16kHz! In the days of 35Hz - 15kHz Hi-Fi that was superb! Nothing much has changed since then. Some MM cartridges are 0.65H, some are 0.4H, but they're near as damn it 0.5H as to make little difference. You will get a dB or so peak around the 16kHz point, but try and remove the capacitance to make it "flat" and it won't sound right at all. Arm wiring plus turntable interconnect contribute on average 70-100pF, and most fixed value phono preamps 100pF, which is close enough. A 220pf phono input will just add to the "sparkle", plus it will turn down interference frequencies a tad sooner. Older Ortofons needed around 400pF, and could sound coarse and lifeless, which led to Ortofon issuing an inline phono adapter with a 220pF capacitor inside. Hoping this helps your understanding. |
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Paul H
Senior Member Joined: 13 Mar 2016 Location: Nottingham Status: Offline Points: 121 |
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Graham, thanks so much for taking the time out to comment. That information is really helpful.
I should, maybe, confirm that I'm not trying to remove capacitance, just to reduce it to a point where it doesn't negatively affect the music I'm listening to. My previous calculations (which were extremely rough and ready) suggested that I had a capacitance in my system of pretty close to 600 pF. With a cartridge inductance of 0.7H, it gave me a frequency peak at around 8-9kHz. I'm trying to reduce capacitance such that I can get that frequency peak to a point where it doesn't affect my listening. I would assume - given that my hearing extends to roughly 15kHz - that a peak somewhere in that region won't be audible and is, therefore, desirable in a system where the high frequencies can sound a little harsh anyway.
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ProJect 1Xpression Carbon UKX w/ Ortofon 2M Black; Arcam Alpha 7 CD player; Graham Slee Revelation M pre; Denon PMA 355UK amp; Epos K1 speakers; Blue Jeans LC-1 interconnects. Room: 2.9m x 3.1m.
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Graham Slee
Admin Group Retired Joined: 11 Jan 2008 Location: South Yorkshire Status: Offline Points: 16298 |
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It is only the phono section input plus the arm/cable wiring which contributes to the cartridge loading. With 600pF the peak will happen at 7766Hz using a 0.7H cartridge. It is a good idea for the arm/cable capacitance to remain at 70 - 100pF because that way it will work with other phono inputs. The input socket contributes around 5pF and can be ignored. I don't know what turntable you're using or amplifier so cannot comment on what they are contributing. edit: just spotted the TT and amp in your signature. It's a bit hard to believe that Denon would use such a large capacitive load? Edited by Graham Slee - 16 Mar 2016 at 4:13pm |
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Paul H
Senior Member Joined: 13 Mar 2016 Location: Nottingham Status: Offline Points: 121 |
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Hi Graham, my system is listed at the bottom of my posts.
At present I'm running a 12.2pf (!) low cap Blue Jeans LC-1 cable (approx 2ft) from Project 1Xpression Carbon table (with the factory fitted 9"
Carbon Fibre Evolution tonearm) to my Denon PMA 355UK amp's phono stage. However, I have a homemade (not by me) mono switch that I've temporarily removed but ultimately would like to put back in my system (note: I'm about to loan one of your pre-amps, hopefully, and my intention is to ensure it comes with said switch). I hoping to get the overall capacitance between cart and amp down to between 150-300pF as per the 2M Blue's spec. I understand the lower the better in terms of cap.
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ProJect 1Xpression Carbon UKX w/ Ortofon 2M Black; Arcam Alpha 7 CD player; Graham Slee Revelation M pre; Denon PMA 355UK amp; Epos K1 speakers; Blue Jeans LC-1 interconnects. Room: 2.9m x 3.1m.
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