Yup.. Only the AQ 6 has the all 4 fan headers that can be used as PWM & Voltage control, The AQ LT if left as Standard would give you a 1 x PWM or Volt + 3 Volt controlled fans, But both units would need to be used as separate devices (NOT Connected to a Main Aquaero unit via the Aquabus). If you use the AQ LT as slave device then you just get 4 x extra Volt controlled fan headers (the LT device looses it's 4th fan PWM function when it is flashed to be used as a slave device) and can be connected to a Main unit Aquaero 6 or 5 Via the high speed Aquabus and therefore is controlled through the main unit Aquaero Menu's...
The PA Devices also only support Volt control over it's one fan header & no PWM as you also noticed
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N.