Hi, I am trying to gauge the manner in which the Threshold S/500 operates in Class A mode given the impedance characteristics of a pair of Sound Labs.
Would someone assist with information on how the S/500 operates in Class A at an impedance other than the nominal 8 ohm rating, for instance a 1 or 2 ohm load. It seems the amplifier operates in Class A up to 20% of its nominal power rating(250 Watts into an 8 ohm load).
Apparently some if not most Class A functioning amplifiers exhibit a phenomenon called "de-rating," whereby there's a reduction in Class A power at lower impedance(Exceptions to this phenomenon comprising the likes of the Pass Aleph series and probably the Classe DR-3-VHC); and it looks like some Class A/AB amplifiers don't even operate in Class A where the load is anything lower than the nominal impedance rating.
Does the Threshold operate in Class A at impedance levels lower than 8 ohms? If it does operate in Class A at these levels, does it exhibit the de-rating phenomenon described above?
Thanks for your help.
Would someone assist with information on how the S/500 operates in Class A at an impedance other than the nominal 8 ohm rating, for instance a 1 or 2 ohm load. It seems the amplifier operates in Class A up to 20% of its nominal power rating(250 Watts into an 8 ohm load).
Apparently some if not most Class A functioning amplifiers exhibit a phenomenon called "de-rating," whereby there's a reduction in Class A power at lower impedance(Exceptions to this phenomenon comprising the likes of the Pass Aleph series and probably the Classe DR-3-VHC); and it looks like some Class A/AB amplifiers don't even operate in Class A where the load is anything lower than the nominal impedance rating.
Does the Threshold operate in Class A at impedance levels lower than 8 ohms? If it does operate in Class A at these levels, does it exhibit the de-rating phenomenon described above?
Thanks for your help.
Last edited:
All amps behave like this. A quick calc shows the S500 makes 13W RMS into 8ohms, 6.5W/4ohms, 3.25W/2ohms.
D
Deleted member 316927
In reply to: "All amps behave like this. A quick calc shows the S500 makes 13W RMS into 8ohms, 6.5W/4ohms, 3.25W/2ohms."
Seems the above response is just a bit hastily miscalculated and prone to misinforming technical research efforts and working environments:
Linear amps like the Kinergetics Research KBA-75 operate in Class A doubling power from 8ohms, to 4ohms, and to 2ohms. See https://www.audiosciencereview.com/forum/index.php?threads/new-member-from-gouda.10614/page-3); and then there are some amps that by their engineering nature exhibit less than double the power output. Another instance is the Class DR-3 VHC, rated at 45 watts into 8ohms, it outputs roughly 360 watts into a 1ohm load. See http://www.apogeeacoustics.com/oldforum/005380-2.html:
From technical specifications and user/technical expert input, the Threshold operates in Class A up to 20% of its rated output power which puts it at 50 watts Class A operation into an 8ohm load (Folks in the community, please correct me if this is an inaccurate specification characteristic); but still wondering if it suffers the derating issue with decreasing impedance or is another exception to the textbook Class A requirements.
This particular unit works in conjunction with a pair of Sound Labs. Appreciate the community's time and efforts providing clarifying input.
Seems the above response is just a bit hastily miscalculated and prone to misinforming technical research efforts and working environments:
Linear amps like the Kinergetics Research KBA-75 operate in Class A doubling power from 8ohms, to 4ohms, and to 2ohms. See https://www.audiosciencereview.com/forum/index.php?threads/new-member-from-gouda.10614/page-3); and then there are some amps that by their engineering nature exhibit less than double the power output. Another instance is the Class DR-3 VHC, rated at 45 watts into 8ohms, it outputs roughly 360 watts into a 1ohm load. See http://www.apogeeacoustics.com/oldforum/005380-2.html:
“The technique of Pure Class A is thoroughly demonstrated in the DR-3 amplifier. At its specified output power, it does not suffer from "derating", a reduction of Class A power at low impedances. No Class A amplifier escapes this phenomenon at some point - to do so would imply a bias current of infinity and a load impedance of zero, which is impossible. However, the DR-3 does go beyond the textbook requirements of Class A operation."
From technical specifications and user/technical expert input, the Threshold operates in Class A up to 20% of its rated output power which puts it at 50 watts Class A operation into an 8ohm load (Folks in the community, please correct me if this is an inaccurate specification characteristic); but still wondering if it suffers the derating issue with decreasing impedance or is another exception to the textbook Class A requirements.
This particular unit works in conjunction with a pair of Sound Labs. Appreciate the community's time and efforts providing clarifying input.