Living With A Class A Tube Amp
I'm ready to replace my venerable Prima Luna Dialogue One amp. Just as I thought I had my choices sufficiently narrowed down, I came across Roger's EHF-100 integrated amp. It has the features I'm looking for without any frills, and has sufficient wattage to power my Sonus Faber Sonetto VIII speakers Checked out their web site and had an informative email conversation with Roger, who confirmed that this would be a good amp for my speaker. s and room. He provided me with some useful information, but I need some info from Class A tube amp owners generally.
From what I gather Class A amps produce max power at all times, therefore run hotter than a typical amp. How does this affect amp placement? My current amp is on a heavy wooden table and in front of a curtained window. Would the table need to be replaced? Do I need Nomex curtains? How does this heat affect tube life? Any other internal components subject to accelerated aging due to the heat? Any other thoughts from Class A amp owners would be greatly appreciated.
Thanks,
John Cotner
New Ulm, MN
@immatthewj If the amp really is class A, you do run them as hard. How loud you play the system has no bearing on the heat or tube life. If the amp is class A1, if you were to put an Ammeter in series with the AC line, you'd find the current draw unchanged regardless if the amp is at idle or full power.
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quoting from my owner's manual: "CIRCUIT TYPE: Push-Pull Ultralinear Amplification in Pure Class A" then "POWER OUTPUT 50 watts-Triode 100 watts - ultralinear." As always, I defer to your knowledge on these subjects. I had just assumed that when I was blasting away at ear bleed levels and the room was getting warmer the output tubes were taking a beating. I also acknowledge that a lot of my preconceived notions are often wrong. I will say that this current set of EL34s is holding up better than the last set, but I am sure that there could be other reasons for that.
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@immatthewj Class A, if we are talking about tubes, comes in three flavors, A1, A2 and A3 (recently patented). If the amp really does get hotter when you push it and it really is class A, then its class A2. In class A2, grid current can exist during part of the audio waveform so the driver has to be a bit more robust in order to maintain linearity during that portion of the cycle. Our OTLs are class A2. |
@atmasphere , thank you for the explanation--that is interesting and makes me a better informed hobbyist. "Pure Class A" was a direct quote from the owner's manual, so that is all I know about it, as my ability to comprehend electrical theory is limited. I always thought the room got warmer when I used to crank it way up, but that typed, these days I listen at low to moderate levels, and after a couple of hours, if I put the palm of my hand on one of the transformers, it is hot enough to make me remove it (my hand) fairly quickly. And, after a few hours of listening at low to moderate levels the room still gets warm. So I do not know for sure that making it scream had it running hotter or not--I just felt that it must be; and I also do not know which category of Class A Cary was referring to by "Pure Class A"; until now, I was not aware of the different categories. If it makes a difference as to how hot it gets, these days I always run it in triode. |
