It warms the music, the soul, and a good part of your room 
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My Dreadnaught is biased pretty high into Class A, and indeed does generate plenty of heat at idle. I leave it off for the most part, since it consumes something like 225W at idle across all four channels. Just need to let it warm up for a bit before any listening session. Someday I may try to sell it and buy something that uses less juice overall, but I enjoy how it sounds and it looks pretty kickass sitting there so I don’t know.
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In a Class A amplifier (single-ended or push-pull), the output transistors (or tubes) are always conducting current, even when there’s no audio signal (i.e., during silence).
• They are biased so that they operate in their most linear region over the entire 360° of the audio waveform.
• The full quiescent (idle) current flows constantly, regardless of how loud you’re playing. This means the amplifier is dissipating maximum heat even when no music is playing.
Yep I get it now. It is always burning roughly half the max voltage potential. That becomes the typical 0 point where half the wave can go above and the other half below. Biasing to get max amplitude between 0v and max voltage (not prematurely clipping at only the high or low point).
It’s drawing FULL power (or close to it) from the wall constantly.
I have a pair of ACAs that I’ve been using for a couple of years. I’ve never actually measured the temp of the heatsinks, but I don’t feel like they get all that hot. I wouldn’t want to lay my hand on there for several minutes or anything, but you can easily touch them without fear. I also just built a pair of the Pass designed Zenductor 2s. Amazing little amps!
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Tom did a fantastic job with the boards! Incorporated a few mods; different MOSFETs and Caps (mains, and added 2 bypass caps to the build).
Got it together today, powered it up and playing > no smoke😎. My main amp (legacy- which will now just run the woofers) went back for a check- so can’t yet play my main bi-amped speakers. Just pulled out some old ratshack minimus to try it out (so any serious listening will be down the road). While I be using this amp for the Heils in a 2-way, the little amp has more than enough oomph to run a mid/tw in a three way. So far so good, and I’m stoked ‘bout getting a little N. Pass Class A. Clearly not the SIT4, but at < 1/10 the cost I’m pretty happy.
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I really like the orange!
TBH, it was nice to work with a brand new, clean circuit board for a change.
I’m measuring 122-125 along heatsinks, 112 on the top, and the faceplate sees about 110. I have it sitting on fans built into the shelf - running at lowest speed ( 1 of 6 ) brings temps down 10 to ~ 20 degrees - so good for my shelf positioning.
Good to see we are getting the same temps. And your fans seem to be doing a great job!
Not to hijack my own post - but it’s been years (decades?) since I played my old minimus 7s, and kinda surprised with these little speakers. They handle the vocals very nicely. Years ago someone brought a pair of these with upgraded Xovers to an event, and I was impressed.
‘fraid my better half may doubt my need to have much larger speakers in the living room…
Likely me if they were white or black. I did a revamp called Synchaetas.
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They were black. Could be, I was thinking Ed? Anyway, whomever, they sounded really nice, and much bigger than they look!
Got my amp back from Legacy, and now just using 2 channels for the woofers, and the ACAmp for the Heils. I will need to get the levels dialed in, and play around with the crossover settings, but I just wanted to get a little music going.
Now, finally, the speakers are very quiet - absent the previous annoying static hiss / hum. Mostly my issue as I found an interconnect cable issue. And I’m very pleased that the ACAmp is silent (as is the legacy now).
thx again Tom
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