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RCruz 16th June 2010 10:34 PM

Audio Technica 33 PTG
 
Hi

I am planning to use an Audio Technica 33PTG cartridge and would apreciate information regarding its best loading in ohm.

A good friend of mine suggested 180 - 220r so that will be my first attempt but as this is a critical build, I would like some more opinions.

Regards

Ricardo

RCruz 17th June 2010 09:31 AM

I have been informed the AT 33PTG is happy with 30~40 ohms.

Any comments ?

I am searching the net and I believe the EAR phono preamp 834P uses a step up TX that loads the MC cart with 50 ohms.... am I getting closer ?

Regards

Ricardo

merlin el mago 17th June 2010 10:48 AM

Becarefor Ricardo, step-up impedance isn't the same that a load resistor. Vinylengine suggest a minimum load resistor of 20 ohms or more

The coil resistance is 17Ω, so the load impedance is 94x the coil resistance. Any value greater than 10x is usually OK.

The series combination of coil inductance and load resistance will have a -3dB point at R/(2πL)

For example if you choose 170 ohms / 2π x 0.070uH (coil inductance) = -3dB at 386Hz

Mine advice is try to left out the -3dB of the ear bandwith in this case is more easy to do with lower resistance possible so:

20 ohms / 2π x 0.070uH (coil inductance) = -3dB at 45Hz not bad far away from mids-lows it's a good choice

That's always theoretically of course fine adjust by ear.

RCruz 17th June 2010 11:25 AM

Where did you find the value 0.070uH ?

Here: http://www.audiocubes2.com/product/A...Cartridge.html

I can read Coil inductance: 70 mu H (1kHz)

I am quite confused with the units :(

merlin el mago 17th June 2010 11:35 AM

AT33PTG Audio Technica?Greater China?Limited

Sorry are 0.070H = 70uH but the calculations are well done only a typo.

merlin el mago 17th June 2010 12:30 PM

Sorry bad calculated, I trust in Audio Technica web so 70uH = 0.00007H

-3dB point at R/(2πL)

100 ohms / 2π x 0.00007H = -3dB at 227.355Hz very good out of ear bandwith

If was milihenry like Audiocubes web 70mH = 0.07H

100 ohms / 2π x 0.07H = -3dB at 227Hz very bad mid-low range bandwith

I doubt Audiocubes specs, seems the coil inductance very high for a small magnet wire....

RCruz 17th June 2010 01:15 PM

I guess the real value should be 0.7mH (0.0007H)

In this case using 170r I would get 38k6 bandwidth (Hagerman Technology LLC: Cartridge Loading)

Salas indicated me to use between 180 and 220.... I guess 180 should perfectly do it :)

merlin el mago 17th June 2010 03:31 PM

0.7mH = 700H = 0.0007H
70H = 0.07mH = 0.00007H

Inductance Conversion - FREE Unit Converter

Don't worry about the bandwith with 180 ohms:
0.7mH = 40.946 KHz
0.07mH = 409.463 KHz

Mine Denon DL103R has a coil Inductance: 56H....


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