Documentazione sul Bruel & Kjaer - 2609 :
http://www.technicalaudio.com/pdf/Bruel&Kjaer/Bruel&Kjaer_Measuring_Amplifier_Audio_Frequency_2609.pdf
Forum :
http://www.diyaudio.com/forums/equipment-and-tools/289411-bruel-kjaer-2609-measuring-amplifier.html
