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Conrad Johnson ART amps - Watts at 8 ohms vs 4 ohms

I had always thought of the ART150 and ART300 as being a 150 watt and 300 watt amp, respectively. Recently I noticed that on their website they are in fact rated as 150 watts into 4 ohms, and 300 watts in to 4 ohms. I've read that in many cases what puts out 200 watts at 8 ohms, for example, will put out 400 watts at 4 ohms, 800 watts at 2 ohms, 100 watts at 16 ohms, etc.
In this case, it would mean the ART150 generates 75 watts into 8 ohms (150 into 4), which does not sound right.
Can anyone shed some light on what these amps put out at 8 ohms? Would be appreciated. Plan on asking CJ directly as well and will certainly report back what they say, if it's of interest to anyone.

https://conradjohnson.com/art150-and-art300-amplifiers/

150 Watts rms per channel from 30 Hz to 15 KHz at no more than 1.5 % THD into 4 ohms (also available connected for 16 ohm loads)

300 Watts rms from 30 Hz to 15 KHz at no more than 1.5 % THD into 4 ohms (also available connected for 16 ohm loads)
gmercer
almarg's avatar
almarg
9,670 posts
 
Can anyone shed some light on what these amps put out at 8 ohms? Would be appreciated. Plan on asking CJ directly as well and will certainly report back what they say, if it’s of interest to anyone.

It appears in this case that the particular amps only provide a single output tap, which is normally wired to provide the rated 150 or 300 watts into 4 ohms. (Per the statement quoted by the OP from the CJ website they can optionally be wired such that they can presumably provide those power capabilities into 16 ohms).

Given that, and given the lack of an 8 ohm specification and relevant measurements, I would not want to speculate as to how much power these amps can provide into an 8 ohm load. Or, for that matter, how optimal a match an 8 ohm load would be in terms of sonics. Let’s see what CJ has to say when they respond to the OP’s inquiry.

Regards,

-- Al
gmercer OP
193 posts
 
For everyone's benefit here are some specifications for the ART-150:
Power output into 4 ohms is 150 watts. Power output into 8 ohm is 101 watts.

With the above information, which comes from CJ, I would suggest that the ART300s (which put 300 watts into 4) will put about 200 into 8 ohms.
batman1971
96 posts
 
Not sure how they are getting those power ratings with only 2  kt 150 per channel   Seems dreamy.   
gmercer OP
193 posts
 
@batman1971 I've heard before that CJ extracts every ounce out of the tubes in a way that no one else does. I listened to the amps a couple times before and I do not doubt the 100wpc rating based on those experiences.
The VAC Signature 200iQ puts out 100wpc with 4 tubes as well, 2 per channel, and that is using KT88s (versus the KT150s found in the CJs).
My dream amp would be a 200 wpc stereoblock from CJ, wish they would.
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