Thanks for the tip so I won't fry my audio board
I bought the non-alkaline AAs because the alkalines are about 4 times the price. Four Panasonic non-alkaline AAs will cost about R$ 2,00. Two alkaline from the major brands (Panasonic, Duracell, etc) AAs will cost about R$ 4,00 or more.
So I guess the non-alkalines are more cost effective here in Brazil.
As for the 9V batteries, non-alkalines will cost about R$ 4,00. Alkalines will cost more than R$ 8,00.
It took me about four and a half days of continuous use to deplete a standard Duracell 9V battery, wich costs about R$ 10, with my zapper/SP assembly. I don't know if their charge is different from the ones in the USA.
A rechargeable 9V of 200 mAh will cost R$ 15,00 to 20,00. A double charger will cost about the same. So going 24h/7d with a SP costs a initial investment of about R$ 80,00, wich is still better than spending R$ 15 to 20,00 every week in 9V batteries (quite a bite in the budget).
So rechargeable 9V are a must here if you plan to run the SP with 9V batteries 24h/7d.
For the sake of comparison the Brazilian minimum wage is about 620,00 R$ per month (hard to live with). 20 kilograms of ortoftalic polyester resin costs about R$ 230,00 without shipment. Current "Real" to Dollar quotation is of about R$ 1,78 to each 1 Dollar.