Impedance Matching for McIntosh C2300 and Sumiko Blue Point No. 2

[mgbaron]

First of all, I'm a newb when it comes to analog audio, so please excuse my ignorance. I tried researching this question before posting, but I'm not finding the answers I'm looking for.

I'm using a Project Xperience Classic TT which is equipped with a Sumiko Blue Point No. 2 cartridge directly to the moving coil phono stage in my McIntosh C2300. I noticed a pretty huge improvement in sound quality when I raised the PHMC impedance setting on the preamp from the default 25 ohms. Currently I have the setting at 200 or 500ohms which seems pretty good to my ear.

From what I understand, this impedance is supposed to be matched to the cartridge, but I can't find anything on what is best for my Sumiko cartridge.

Anyone have any ideas what this setting should be set to or how to find out? What are the trade offs of going up or down?

Thanks!

[jdandy]

Matt.......The C2300 moving magnet phono stage input is preset at 47K ohms and cannot be adjusted. The setting you are making changes to is the capacitance loading which can impact a moving magnet cartridge performance, but more often than not the performance of a moving coil cartridge is not affected by changes in capacitance.

Your Sumiko Blue Point No. 2 is a high output moving coil cartridge with a 47K load impedance. It should work perfectly with either the moving magnet or moving coil inputs on the C2300.

Sumiko Blue Point No. 2 Specifications:

•High output moving coil phono cartridge
•0.3mm by 0.7 mm elliptical diamond stylus
•Frequency Response 15Hz-35KHz
•Output Voltage/Channel 2.5mV
•Channel Separation 32dB
•Channel Balance 0.5dB
•Compliance (x10-6 cm/dyne) 15
•Stylus Size/Shape .3x.7/Elliptical
•Load Impedance 47k Ohms
•Tracking Force Range 1.6-2.0 grams
•Recommended Force 1.8 grams
•Cartridge Weight 6.3 grams

[mgbaron]

Thanks, Dan, but I'm still a little confused and noticed I had a typo in my initial post that might have led to confusion. To be clear, I'm using the moving coil input on the C2300. Here's what the manual says on the setting I'm adjusting:

1. Select either the Phono MM or Phono MC Input
using the INPUT Control.
2. Rotate the TRIM SELECT Control or press the
TRIM Push-button on the Remote Control until
“PHMM _ _ _ PF” or “PHMC _ _ _ OHM”
appears on the Front Panel Alphanumeric Display.
Refer to figures 22 and 23.
3. Rotate the TRIM ADJUST Control or press the
LEVEL + / - Push-buttons to select from the
available values of cartridge loading (Ohms for a
Moving Coil Cartridge or Capacitance for a Moving Magnet Cartridge) that comes closest to the
Cartridge Makers recommended value

Since I am using the moving coil phono stage, I think I am adjusting the impedance. I'm noticing a pretty big impact on the sound. What is going on? What should it be set to? What are the tradeoffs?

[jdandy]

Matt.......I see you edited your original post to reflect the moving coil input. That makes all the difference in the world. So, yes you are adjusting the load impedance. You will notice quit a difference in the overall frequency response of the moving coil cartridge when adding or subtracting load impedance. Since the Sumiko Blue Point No. 2 load impedance is 47K ohms, I would expect the higher you set the C2300's moving coil load impedance the more open and clear the top end of your Blue Point's frequency range will sound. There is no hard and fast rule on load settings. What sounds best to you is the correct setting.

[mgbaron]

Thanks, Dan. I'll keep playing with it and see what works best. So far about 200 ohms seems to be about right. I wanted to make sure there was no science to it.