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Ain't the brightest bulb in the box

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GDHAL:
It's not clear from your post whether or not "250 W and 16 Amp continuous current" is the amplifiers power draw, or power output.

In any case that has nothing to do with the type of amplification class.

As to the wattage output normally manufacturers state the specification in terms of each channel, if it's a two channel amplifier. So in your example it should be 150 watts per channel into 8 ohms

HAL:
Class AB is a linear amplifier output stage, so not totally Class A.  Usually that spec is for its continuous RMS output power per channel.  That is a lot of current for an output stage to deliver, so it has a hefty power supply!

steve:

--- Quote from: dflee on March 09, 2023, 09:02:49 AM ---Finally found some info on the unit.
Diyaudio has a section from LazyCat (designer) and states 250 W and 16 Amp continuous current. They do state it as a class A/B.

Max Power 8 Ohm   150 Watt 0.05 THD   
Max Power 4 Ohm   230 Watt 0.05 THD   
Bandwidth   3 Hz to 3 MHz (-3dB)
THD   0.0034% (100 Watt)   
IMD   0.003%
SNR   110 dB
Input Impedance   10 Kohm
Damping Factor   >2000 (4 ohm)
Year Introduction   2014
Does continuous current mean class A? And am I right assuming it's 75 per channel into 8 Ohm?

--- End quote ---

Hi Don,

Describing is rather difficult, but I will try to be as clear as possible. Please bear with me.

Yes, 75 watts per Push Pull channel into 8 ohms, the current flow is ~3.06 amps per channel.
Times two channels is 6.12 amps.

Per the designer's comment 250 watts/channel rms into 4 ohms, the current flow is ~7.9 amps rms.
Times two channels is 15.8 amps rms. He is stating the power supply can power both channels to
the max without an "unscheduled disassembly" of itself.

However, what determines whether operation is Class A or Class AB is determined mainly by the
output devices and device parameters chosen (although the power supply has to be designed to power
whatever Class is chosen). (Collector voltage, bias current etc etc)

Since Class A is so inefficient, even 16 amp current rating would not provide 250 watts output
into 4 ohms. Theoretical maximum efficiency is 50%, but figure 30% plus/minus.

Operating Push Pull AB is interesting as, depending upon the idle bias, both transistors (tubes)
operate Class A over a range of X few output watts before each transistor starts to shut off over a
portion of the waveform/cycle. At that point, AB operation commences. Class A X power output depends
upon the idle current (with no signal), size of the device(s) etc etc.

Sometimes I am not very clear, but hope this helps some Don.

steve

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