Cartridge loading plugs
Printed From: Graham Slee Hifi System Components
Category: Turntable Audio
Forum Name: High Fidelity Turntable User
Forum Description: Technical Q&A, hints and tips
URL: https://www.hifisystemcomponents.com/forum/forum_posts.asp?TID=1246
Printed Date: 23 Apr 2024 at 7:26pm
Software Version: Web Wiz Forums 12.01 - http://www.webwizforums.com
Topic: Cartridge loading plugs
Posted By: tg [RIP]
Subject: Cartridge loading plugs
Date Posted: 24 Nov 2011 at 11:10am
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From time to time there is interest in varying the loading of various cartridges.
As a reference to mention of one particular application of this, I refer to my review of the Genera phono preamp -
This method allows trial of various loads without equipment modification. The required components are readily available and minimal soldering is required. To use the plugs a pair of 2F -> 1M RCA/Cinch "T" adaptors are required. These will be plugged into the inputs of the phono stage/active headamp (I use them on the input to the Elevator Exp to achieve loadings not available via the front panel switches). A pair of cheap phono/RCA plugs and a pair of the appropriate resistors are required to make the load plugs, the resistor is soldered across the terminals of the plug and the plug inserted into the branch of the adaptor. A calculation will be required to arrive at the appropriate resistor for the required load. Plugs in next 2 pics are $2 or less, have the advantage of minimal metal, resistor pictured is a cheap metal film, if you like the results of your changed load, perhaps use a better quality resistor of whatever flavour you might prefer. I am presently using Takman Carbon Film. Since I have made up a number of these with different resistors, I mark the body with the resistor value using a CD labelling pen.
Plugs and adaptors fitted to end of tonearm cable of SL1200 ready for insertion in phono stage
Plugs in use on Elevator Exp
------------- Tony G |
Graham once asked if the HOMC DL-110 produced more surface noise than the AT-95, an issue to which I had not previously paid attention.
Replies:
Posted By: Graham Slee
Date Posted: 24 Nov 2011 at 4:53pm
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Bloomin' excellent article tg! Now for the maths! As the phono stage should already be 47k then if you want say 30k you add a resistor in parallel to make 30k, but that's not going to be a 30k resistor at all, because 30k in parallel with 47k is... 1/((1/47) + (1/30)) k = 18.31k This is how you work it out (for this 30k example)... 1/((1/30) - (1/47)) k = 82.94k (nearest value is 82k) I bet that seems daunting doesn't it? So, here's the key sequence on a simple supermarket scientific calculator (like the kids use at school these days)... Instead of 30 I'm going to put X... X is your desired value! [X] [x-1] [-] [4] [7] [x-1] [=] [x-1] [=] Just replace the X with your desired value and it'll give the resistor value you require - then pick the nearest available from whatever catalogue you buy from. So long as the desired value is in k Ohms the answer is in k Ohms and the key sequence works! ------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Posted By: oldagetraveller
Date Posted: 30 Nov 2011 at 10:58am
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I've tried this on the Denon DL110 tg, following your excellent post, using cheap plastic phono plugs, a 1kOhm metal film resistor in each and two "T" adaptors plugged into my Era Gold. My soldering "skills" leave a lot to be desired but the resistor tails are firmly "glued" to the phono plug terminals and no melted plastic! You are 100% correct about the surface noise, this has virtually disappeared. I have some quite old albums and even with the utmost care and cleaning still display a few crackles. I can't quite decide what's happened to the sound now, there's a definite difference which I think is for the better. In fact yesterday evening I couldn't stop listening to one lp after another! ------------- Peter P T- LPT/RB300/G1042, Pink Triangle Tarantella/Nima/Ortofon 2M Black, SL1210II, Naim CD5, NAC112, NAP150, Flatcap2, Proac SC1, GS SoloUL,GS Accession , Senn HD250 & HD540. |
Posted By: tg [RIP]
Date Posted: 30 Nov 2011 at 12:02pm
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I am glad that you tried it and have reported back on your results. I am a fan of the DL-110 and have been so for a number of years. IIRC the suggestion of an approximate 1K load originally came from Graham, as a result of his looking at a frequency response plot for this cartridge. He noted a rise in the upper frequencies which he thought would increase surface noise and asked the question as to whether this were the case. As you say, the change apart from that is rather subtle but seems to be all good, icing on a very good cake as it were. I think it is always a good sign when you keep playing more records. ------------- Tony G |
Posted By: gaz
Date Posted: 06 Oct 2012 at 9:18am
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hi want to make some loading plugs for reflex c
I'm no good with maths
so can some one help me out please
want loading plugs to give me 470 and 453
thank you
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Posted By: tg [RIP]
Date Posted: 06 Oct 2012 at 10:39am
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Hi Gaz, unfortunately, the Reflex C has, IIRC, a primary loading of 100 ohms. It will not be possible to achieve the loading you desire using parallel loading as pictured here. The total resistance of a parallel pair cannot exceed the resistance of the lesser resistance of the pair, in this case 100 ohms. This method can only be used to reduce the primary resistance not to increase it. What you are looking for will require an increase in series resistance, whether this can be done in a similar way I would have to leave for Graham to advise. ------------- Tony G |
Posted By: Juan Pyrrho
Date Posted: 27 Mar 2013 at 11:38am
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I have added a pair of loading plugs into the back of my Elevator in order to double the load impedance for my Denon DL 304 mc. Previously on the 100 ohm setting I felt the sound was a little thin and lacked a bit of weight. I tried the 840 ohm setting but that sounded too bright and altogether wrong. The addition of two 170 ohm resistor plugs into the 840 ohm setting brings the load impedance up to 203 ohms (approx), effectively doubling the load. Significant improvements in the sound instantaneously !! More weight and the sound has a lot more impact, which was what I was looking for ! I also own a modified VdH MC 10 special where the manufacturer info on the wooden box says 100 ohm and up (as usual) but states 200 ohm as the recommended load. Why don't the cartridge people drop the minimum value load impedance and nail their flags to a recommended value instead ? In my experience varying the cartridge load always significantly changes the overall tone of the system. When I get round to having the vdh retipped I'll be very interested to hear how it sounds. I thoroughly recommend this path as one of most significant, super cost-effective things I've ever done to try & improve my set-up. No scrap that. THE most effective thing.... keep up the good work everyone. |
Posted By: tg [RIP]
Date Posted: 27 Mar 2013 at 2:11pm
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Juan, thank you for sharing your experience with this method of tweaking the cartridge load. Your findings with the DL-304 mirror my own findings with the DL-301 II as to their effect. I would question the 170 ohm (typo perhaps ?) since my calculations yield 270 ohm as the required parallel load with 840 for a 204 ohm equivalent load. IIRC oldagetraveller runs a DL-304, perhaps he might like to try this load too. Always good to find inexpensive tweaks that yield such positive results. Have fun, Tony G ------------- Tony G |
Posted By: Juan Pyrrho
Date Posted: 27 Mar 2013 at 2:39pm
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You are dead right about the resistor values. I got lazy and quoted them from memory rather than checking them out properly. Very remiss of me, As the americans say, " my bad .." well spotted by the man from down under. regards from a cold & miserable East Dulwich, south London.
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Posted By: oldagetraveller
Date Posted: 28 Mar 2013 at 12:41pm
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"IIRC oldagetraveller runs a DL-304, perhaps he might like to try this load too" Yes, he does.  It's actually in use at the moment, on my Tarantella, through Elevator and Reflex M. I'll get hold of some 270 Ohm resistors and give it a go. It might be a few days - there's no way I'm retiring to the garage, in the cold weather we're experiencing at the moment, to rev up the soldering iron! ------------- Peter P T- LPT/RB300/G1042, Pink Triangle Tarantella/Nima/Ortofon 2M Black, SL1210II, Naim CD5, NAC112, NAP150, Flatcap2, Proac SC1, GS SoloUL,GS Accession , Senn HD250 & HD540. |
Posted By: tg [RIP]
Date Posted: 28 Mar 2013 at 2:30pm
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FWIW, I use the 270 ohm plugs with 1K on the front panel for 212 ohms effective with the DL-301. It has just returned from being re built with a ruby cantilever and line contact stylus and is sounding stunning. regards from hot and sultry (0130 hrs and doors open and no shirt on) Dulwich Hill, Inner southern Sydney. Nearly cool enough now for sleeping and the planes have all gone to bed ------------- Tony G |
Posted By: Fatmangolf
Date Posted: 26 Nov 2017 at 12:11pm
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This thread focussed on resistor loading and I wanted to expand it to capacitative loading if that's okay with you Tony (tg)? It struck me that we could use the splitter and loading plugs you describe above for small capacitors too. I can take this into a new thread if you prefer? ------------- 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. |
Posted By: Fatmangolf
Date Posted: 26 Nov 2017 at 12:29pm
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The back story. In other threads Graham explored the impact of changing the
capacitance formed by the tonearm leads and internal components of the
phono preamp. For MM this creates a peak that extends the audio
frequency response to 16kHz or so. For MC it can be used to reduce the
level or electromagnetic signals picked up by the cartridge. For MM I bought a Genera preamp kit from Graham Slee products and really enjoyed the sound it gave me compared to other preamps I owned. I fitted internal switching that allowed me to adjust the capacitative loading and wrote about this elsewhere on this forum. As Graham advised the choice of capacitator type made quite a difference, I really liked the Polypropylene type he suggested - Evox PFR. The Accession MM preamp I now have included external dip switches to change the same loading and probably uses the same parts to even better effect. For MM this is 100pF and 220pF, i.e. pretty small values. At this point I am interested in MC loading. It was a revelation to me that a much higher value than I associated with cartridge loading but the 4.7 nF Graham recommended seems to have improved my records' sound when played back. It had never occurred to me that the LC combination could be used as Graham did, to filter out problem radio and data signals so these didn't interact with the audio. Same formula Fr = 1 / (2 Pi SQRT(LC)). I don't have a Spice circuit simulator but the forumula above and R = SQRT (L/C) are enough to explore some options. As the manufacturer of my MC cartridge doesn't publish its self induction (L above) what I know it that my version has an internal resistance of 7 ohms, which is Rdc not the loading R above! Crudely comparing Rdc and L for other cartridges I concluded mine could be in the 10 to 20 uH range. Graham suggested a similar cartridge at the upper end of my gestimates, a good sign my figures were reasonable. To test the impact I fitted a pair of 4n7F capacitors inside my Elevator EXP. After allowing a day or two for the unit settle down under power I really liked the sound and wanted to explore further on the loading. To get a resonant peak in the 300 kHz range Graham has simulated my optimal loading would be a lot higher that the 4n8F I have now. From the Fr formula about the capacitor would be about 10x higher i.e. more like 50nF or 0.05 uF. I am interested enough to explore this and have an unused third switch on my EXP that accommodate this alongside the existing switched resistor options. To avoid powering down I thought of using phono Y-adaptors as Tony described here. I still have the bits from when I tried this with my Rega Exact feeding another manufacturer's preamp, think Oxbridge you'll know what I mean. In 2010 I picked up an article on cartridge loading that was about MC's and step up transformers. I filled it away on a hard drive and rediscovered it as few days ago. The second half of the article uses the Fr formula above to get an MC peak in the audio range, using capacitor values around 1uF which was an eye opener. It is about 400 times higher than the loading I now! I am pretty happy with the treble response of my Phoenix so I won't be going that far, but it does show what could be done. It is Graham's RFI reduction I am interested and the heterodyning he has identified makes sense to me. Now I need to find some reasonable sounding capacitators in the 10-50pF range and work out how to fit them into phono plugs with some shielding! ------------- 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. |
Posted By: tg [RIP]
Date Posted: 28 Nov 2017 at 3:36pm
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Go for it Jon, I will follow your experiments with interest. This does seem the most pertinent place for such. ------------- Tony G |
Posted By: Fatmangolf
Date Posted: 02 Dec 2017 at 11:10am
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Thank you Tony. I thought your thread deserved a push as it covers everything and is much clearer than similar topics I've seen elsewhere. My starting point will be fitting the Y-adaptors with unterminated phono plugs and going some listening to get a baseline. I will also try them with Audioquest RCA caps. Last time with the resistors I used different colour phono plugs but suspect that won't be possible as the capacitors are bigger. Not really a problem. Parts wise I have a spare pair of 4n7 Evox PFR's so that will be my starting point. As far as I can see that range only goes up to 10nF which I can almost get from two 4n7's in parallel. I also have another 2 pairs of 4n7 Evox PFR caps in my Genera, which has just returned from an extended loan when its user bought their own Accession! So I could get up to 19pF loading with some careful soldering up to the phono plugs, giving Fr 365kHz if L=10uH (R=23 ohms) and 258kHz if L=20uH (R=31 ohms). If L=20uH I would get Fr=365kHz which would be fine. All these numbers seem precise but are based on estimated value of L and tolerance in value of capacitors. They may also be inaudible changes! However calculations are cheap, the electronics equivalent of measuring twice and cutting once. ------------- 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. |
Posted By: Fatmangolf
Date Posted: 01 Feb 2018 at 9:01pm
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Apologies for leaving no readers hanging on the cliff. Adding another 4n7F (well slightly more with the adaptors) made no audible difference to me. I am very happy with my EXP's 4n9F from the 220pF and 4n7F capacitors. ------------- 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. |
Posted By: tg [RIP]
Date Posted: 02 Feb 2018 at 12:56am
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Jon, perhaps you might clarify a point here, you are fitting these capacitors across the leads in the plug here ? (ie same as the resistors) ------------- Tony G |
Posted By: Fatmangolf
Date Posted: 02 Feb 2018 at 6:33am
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Yes, wired just like the resistors on the earlier photos so the capacitors connect from signal to groun. They were connected in parallel with those inside the EXP so increasing the capacitative loading seen by the cartridge. ------------- 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. |