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MC Step-up Transformers by DIY Hi-Fi Supply? Step-up ratios and reflected loads

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Posted on June 1, 2012 at 01:01:01
Timbo in Oz
Audiophile

Posts: 18679
Location: Canberra - in the ACT - SE Australia
Joined: January 30, 2002
Contributor
  Since:
June 25, 2014
"With 1:10X step up, it will have 100 ohm load. With 1:20X step up, it will have 25 ohm load. These two connections can cover 90% of all MC cartridges."

Really?!!?

Did someone pluck these numbers from out of the air?

A 10 times step-up ratio with any other SUT I know of, looking into a 47kohm MM load will give a reflected load to the MC of 47K/(10x10) = 470 ohms, NOT 100ohms.

With a 20 times ratio we are didviding the load by 20x20 = 400, thus giving a reflected load of 117.5ohms that the MC will be working into, ie NOT 25ohms.

For typical MC's requiring a 10 and those a 20 times set-up, the loads I've calculated wil be good GOOD loads for them.

A 100 ohm reflected load (which AFAIK can only be given by a 21.7 step-up ratio) would be a good load for an MC of 10ohms or less coil impedance. Most such have quite low output and 10 times would not CUT it. 20 to 22 will, of course.

A 25 ohm reflected load (which AFAIK can only be given by a times 43.4 step-up ratio) would be a good load for an MC of 2.5 ohms coil impedance or less. The lowest coil impedance I know of on an MC is 3 ohms! And you would neeed a step-up impedance, so they need a load of about 30 ohms or more.

And for this you need a step-up ratio of 30. Which Ortofon's SUTS for their SPUs do provide. What a surprise, eh?

There are a few very low-Z MC's around now with quite high voltage ouputs, which do NOT need such a high step-up ratio, and are alos unlikley to sound wrong when given an easier (higher in ohms load).

New physics?

OR are you trying to con all the 'load your MC low' fashionistas, while actually giving them loads which will sound better? :-^) he says tongue in cheek.

Get it right, folks.


Warmest

Tim Bailey

Skeptical Measurer & Audio Scrounger


 

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RE: MC Step-up Transformers by DIY Hi-Fi Supply? Step-up ratios and reflected loads, posted on October 18, 2012 at 18:00:16
Tre'
Industry Professional

Posts: 11945
Location: So. Cal.
Joined: February 9, 2002
"A 25 ohm reflected load (which AFAIK can only be given by a times 43.4 step-up ratio) would be a good load for an MC of 2.5 ohms coil impedance or less."

To start with, I like your post and understand what you are saying.

But....if you change the 47k resistor in the phono preamp you can get any load you want.


Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

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