IO One internal impedance before it was 1 Ohm

I’m being asked about the internal impedance of my old 2011 IO Can anyone please help?

I hear people talk about and 80:1 step up but I don’t remember anything about impedance changes of older Io’s or what is ideal can any one guide I could guide me what to pass on?
My phono stage has a step up included which is potted in 5lb of wax so I have no idea what it is.

many thanks

It’s 1 Ohm

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I don’t think the design has changed although @murrayjohnson would know better than me.
80:1 sounds about right.
My S6 has a number of imprdance settings, I use the 1 ohm setting

From Audio Note ,manual


Thanks - I think it’s possible they have always been one ohm he is confused with the matching impedance requirement being different from internal.


The Io has always been 1 Ohm but opinions differ on the loading. AN recommend 3 Ohm but I prefer 10 Ohms (after Guy & Pete recommended trying it) and loaded my old step up for 10 and 30.

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I think the internal impedance of the cartridge is 1 Ohm or actually 0.75 Ohms, however what it needs to see, ie be loaded by is more like 7.5-10 Ohms.

The ratio of the original AN Japan transformers like ANS6 or ANS7 when set for the Io is 1:70 so, when the transformer sees the typical 47 KOhm presented by a typical mm phono stage the cartridge sees 9.6 Ohms. (47000/70 squared)

There was a convention with Japanese cartridge and SUT manufacturers to indicate either the required internal impedance or what the transformer presents the cartridge when loaded with 4K7 rather than 47K (possibly because of the rule of thumb that the load seen should be 10x the source. Not sure exactly why but it continues even now with Hashimoto speccing their MC transformers 3 and 40 Ohm when actually what the cartridge sees is 30 or 400 Ohms. 30 Ohms might suit an SPU whereas 400 would suit a Denon 103 or Hana SL.