I also own a AQ PT-9 Arm.
I don't believe the wiring scheme on the DIN (JIN) connector is unusual in any way, that many company's phono cables will work, from an AQ to a Graham, to a PAD Venustas, etc.
I believe what you say is correct, that this Cable will be one of, if not the very most important cable in the entire chain.
The AQ Cables will generally be a safe bet, and if anything ever happens with the cable, or you do not like the cable for whatever reason, all AQ dealers will gladly refund your money, or let you enchange. AQ themselves will stand behing all their products as well, in case a repair is ever needed.
Shielding is critical, to stave off RFI. I use an older AQ Emerald Cable, which I think is a quite good Cable for the money I spent.
Other options would be the Cable Company, that you could try out a number of different Cables. Although I currently do not see him listing any items here on agon, "audiodragon" is a seller here who deals with all of the Jelco products, which the AQ Arm is. His prices are very reasonable. He sells Jelco Tonearm cables as well. You can probably contact him through the agon site with a simple search.
Hope this helps. Mark
