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Cartridge loading plugs

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tg [RIP] View Drop Down
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Post Options Post Options   Thanks (2) Thanks(2)   Quote tg [RIP] Quote  Post ReplyReply Direct Link To This Post Topic: Cartridge loading plugs
    Posted: 24 Nov 2011 at 11:10am

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   -

Quote  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.

On this occasion, I have made the observation that, yes the DL-110 does produce more surface noise than the MM - with the proviso that both use the standard 47K loading.

Adding a 1K loading plug to the Denon not only reduced the surface noise to the level of the MM, it was, in general an improvement that I rather liked, giving a very powerful and memorable performance on Don Juans Reckless Daughter by Joni Mitchell.

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




Edited by tg - 04 Jun 2016 at 8:00am
Tony G
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Post Options Post Options   Thanks (2) Thanks(2)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 24 Nov 2011 at 4:53pm
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!


Edited by Graham Slee - 24 Nov 2011 at 4:55pm
Not simple enough for Google-Bot to understand...
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Post Options Post Options   Thanks (1) Thanks(1)   Quote oldagetraveller Quote  Post ReplyReply Direct Link To This Post Posted: 30 Nov 2011 at 10:58am
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!
 

Edited by oldagetraveller - 30 Nov 2011 at 10:59am
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.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote tg [RIP] Quote  Post ReplyReply Direct Link To This Post Posted: 30 Nov 2011 at 12:02pm

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. Wink  




Edited by tg - 04 Jun 2016 at 8:00am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gaz Quote  Post ReplyReply Direct Link To This Post Posted: 06 Oct 2012 at 9:18am
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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tg [RIP] View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tg [RIP] Quote  Post ReplyReply Direct Link To This Post Posted: 06 Oct 2012 at 10:39am

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.



Edited by tg - 04 Jun 2016 at 8:01am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Juan Pyrrho Quote  Post ReplyReply Direct Link To This Post Posted: 27 Mar 2013 at 11:38am
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.





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