Cartridge loading plugs
Printed From: Graham Slee Hifi System Components
Category: DIY AUDIO
Forum Name: DIY Audio questions and answers
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URL: https://www.hifisystemcomponents.com/forum/forum_posts.asp?TID=349
Printed Date: 27 Mar 2026 at 2:11am
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Topic: Cartridge loading plugs
Posted By: tg [RIP]
Subject: Cartridge loading plugs
Date Posted: 12 Jan 2009 at 8:08am
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This question relates to the construction and use of loading plugs for MC cartridges. Premise, the Exp provides input impedances of 100 Ohm then 840 Ohm, should one wish to load @ say 220 Ohm or 470 Ohm for example, is this possible to achieve by inserting appropriately loaded plugs on the input sockets ? If so, is it as simple as adding the difference as a resistor of say 120 or 370 Ohm to the active line only or how should it be done ? (and are the calculations somewhat more complex ?) |
Replies:
Posted By: Graham Slee
Date Posted: 14 Jan 2009 at 4:19am
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Hi tg, This is something I've been meaning to do for years. I still need to source a suitable plug/socket unit to insert the required load... Ortofon used to do something similar back in the 70's/80's. The resistor is placed in parallel meaning across signal to ground. Example for converting 1k (1,000 Ohms) load setting to 470 Ohms would require 886 Ohms across it. The nearest "prefered" value is going to be 910 Ohms giving 476.44 Ohms (close enough?) The key press formula for working it out on a calculator is... [value you want] [1/X] [-] [current value] [1/X] [=] [1/X] [=] the [current value] needs to be larger than the [value you want] and in the same units - in other words all in Ohms or all in kOhms. testing the formula you get... [470] [1/X] [-] [1000] [1/X] [=] [1/X] [=] [886.7924528] then to check what you get using 910 Ohms... [910] [1/X] [+] [1000] [1/X] [=] [1/X] [=] [476.4397906] (replacing the minus sign with the plus sign this time) clear as *** ???  ------------- That none should be able to park up and enjoy the view without a smartphone and the knowledge in how to use apps |
Posted By: tg [RIP]
Date Posted: 14 Jan 2009 at 8:36am
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Plugging in some real world values for a specific cartridge - DL 102 output 3.0mV, DCR 240 Ohms, recommended load 1K Ohm. http://www3.sympatico.ca/murraya/DenonMonoPage.htm - http://www3.sympatico.ca/murraya/DenonMonoPage.htm shows difference in output into 47K Ohm and 1K Ohm. With this level of output it should run straight in to the Reflex bypassing the Exp so running into 47K Ohm. If I have the calculations right then the required value is 1K02, since this is only available in 1% the most likely substitutes are 1K (oddly) or 1K1 giving a load of 980 or 1070 Ohms respectively, n'est ce pas ? If correct, then I have the general idea, and can move to question the second. Given that finding a suitable adaptor/plug may prove difficult and that the cartridge be mounted in a headshell with removeable fly leads. Is there any reason, other than additional mass in the headshell, why this resistor might not be directly connected across the fly leads immediately at the cartridge output ? |
Posted By: mrarroyo
Date Posted: 14 Feb 2009 at 3:44pm
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Since there is so much variance in resistor values you could get lucky by testing various resitors so their combination could give you the value you want. ------------- Miguel |