Zero autoformers -- how to measure impedance?


Hi guys,

I got a pair of speltz zero autoformers recently but when I measure the total impedance, my multimeter sees only 0.4-0.6 ohm no matter what I do. It seems the multimeter could only read the dc resistance from the autoformer itself but not the total impedance of the speakers and the autoformers. Is this normal? It's blowing my amp into protection mode.

Paul's website does mention something about using these with solid state amps that has excess offset voltages but I have no idea what that means....

Thanks,
Ryan
angelgz2

Showing 4 responses by angelgz2

Hi Al and Bombaywalla

Thanks for the inputs. I am glad that the zeros didn't fry. My bad, the -22.6 is in mV as indicated on the multimeter. I have one pair of speakers connect to it but will measure again taking everything off. Thanks!
Thanks Al and Bombaywalla. I figured this is a separate topic so I started a new thread. I hope I didn't fry the zeros. I have an amp and a receiver. The zeros were originally connected to a NAD T757 V2 and this unit kept going into protection. Yesterday, I rewired it to the Parasound new classic 5125 (connected to the front pre-outs of the T757) and no more protection mode and the amps are not hot at all.

While it was connected to the T757, I can feel a relatively high current on the binding posts where the zeros are connected to the receiver. When I put my fingers on these binding posts, the current "zaps" my fingers a bit but not that bad.

I hope I didn't fry the zeros did I? I mean, how can they be fried since they didn't get hot at all and I've only ran them on the NAD unit for no more than 2 hours. I'll get a reading on the DC output on the NAD unit today and hopefully we can come to a conclusion whether they are fried.
Hi Al,

I measured the DC output of the NAD T757 and found it to be -22.6. How can it be negative? Is that normal?

Thanks,
Ryan
I did another measurement with everything disconnected. The unit has already been on for a while. The measurement read -2.0mV on the front channels and -1.9 on the surround channels. So I take this is normal since the voltage is practically zero?

I've ran the zeros with the Parasound amp using the NAD as a pre amp for over 5 hours last night with movies and music and neither unit gets hot or enter into protection mode. The speakers sounds much better than before. Unlike using a 3ohm in-line resistor, they no longer sound like someone speaking in a box. The 1.5 ohm resistor definitely helped preventing the 4 ohm woofer from sounding too loud.

I would definitely call this a success. Thanks to all for your help completing this project!! God bless you all

Thanks,
Ryan Huang