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Parallel or Series?

98.117.181.4

In Reply to: RE: My first question is posted by 1973shovel on October 14, 2009 at 05:36:26

The cart is an AT150MLX, the phono stage is a Phonomena II that Michael Yee is customizing for me to give alternate capacitance loading. The phono stage comes with a native 50K loading for MM, but also a 100K setting.

The loading in the phono stage is a somewhat complex parallel circuit controlled by various dip switches. If seems that if I add a resistor to an RCA-style between the unit and the phono cable it would be in series and that its resistance would be additive to the resistance of the parallel circuit inside the unit?

I know DB systems has a set of capacitance and resistance plugs that work off a Y adapter, but I would like to confirm how they wire the resistor into the plug.

My desire to get a 61.8K loading is based on using the Hagerman loading calculator. It is really just an experiment, but there are people working with alternate loading strategies with MM carts.

Five what is what I see used. It may be overkill, but that is why I have posted so I can field responses like yours and refine.

How do you wire a resistor plug and why is it parellel? If parallel it seems a 160K resistor would bring it down to the desired range?

Follow Ups:

Parallel - 1973shovel 06:45:53 10/14/09 (2)
I understand why it seems like it would be in series, but it's parallel. I used your male/female RCA method to determine the proper loading for my Denon 103R. The phono had a 47k input impedance, and I used a 100 ohm resistor on the male RCA to give me aprox. 100 ohm loading for the Denon.

Were it in series, I'd have ended up with 47,100 ohms.

You were correct that the resistor is soldered from the + to the - of the male RCA plug. It's parallel because both resistors are tied to ground in this configuration.

I was surprised to see the 100k setting on your Phonomena II, but checked it out, and sure enough, it's there. As Ron pointed out, resistors in parallel can only be LESS, so start with the 100k dip switch, and calculate your necessary resistor from there to hit your 62k mark.

I'm also curious where you've seen 5 watt resistors being used for phono loading. A high wattage resistor isn't a problem (except perhaps in quality) but it certainly isn't necessary as the voltage and current generated by a phono cartridge is exceptionally low. If you are set on a 5w resistor, I'd use a Mills, not an inexpensive sand cast type.

Good luck with the higher impedance loading experiment. Interesting stuff.
- Ordered some Rikens - jupiterboy 07:42:26 10/14/09 (1)
  at 160K .5 watt, and a few other bits. It should be very interesting. Thanks for the input.
  - Riken - 1973shovel 09:30:13 10/14/09 (0)
    They're a good resistor. Glad to help.

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