Living With A Class A Tube Amp

Uh Huh....

I have Sonus Faber Amati which I am powering with 70wpc of triode tube power. It is more than sufficient. So, I would think the Rogers amp should be fine.

I cannot imagine there is anything wrong with your placement. The tubes are in the front. They are not going to get that hot. Running in class A will reduce the tube life.. so the output tubes will need to be replaced more often… maybe 2,000 hours… ask Mr. Rogers, and check on line about the price of replacements. I doubt it is a big deal.

Finally. Sure they use more power. So what… how long do you have them on a day? An hour? When my air conditioner is on round the clock it cost two or three bucks a day… and the amp is going to be a fraction of the power.

Thanks for the useful information.  I'm not concerned about household power usage, since the amp is on no more than four hours a day.  But I do want to have my eyes open if the tubes need to be replaced more often, which is an expense worth considering.

This is not a class A amp. It is a push pull.

@carlsbad2 Push pull amps can be class A no worries. The Dynaco SCA35 using a pair of EL84s was a class A PP integrated amp. We’ve been making class A triode PP OTLs for decades.

If you were not aware that amps other than SETs can be class A, now you are. The trick is just the same as in an SET- the power tubes do not go into cutoff during any portion of the output waveform right up to full power. So you can also have class A solid state PP amps too.

@jrcotner Tube amps running class A have hotter running power tubes and that always means shorter tube life on account of the heat. To get the most out of the tubes they should be kept free of dust and fingerprints, have adequate ventilation and the speaker load should be benign (they will run hotter if the speaker is 4 Ohms on the 8 Ohm tap for example, because more of the power they make will be dissipated in the tubes themselves rather than in the load).

There are amps of other classes of operation now that have all the good properties of the best of class A; this is true of even some class D amps now.

The reason for class A is to maximize linearity out of the output section; the less work the feedback (if any) has to do to correct the output the better. In the old days I think one concern was crossover distortion but I’ve yet to see a PP amp that actually had a problem with this as long as it was biased correctly.

In case you’re not aware of it, the differences you hear between amps is mostly the different ways those amp make distortion. IOW the distortion signature of the amp is also its ’sonic signature’. Once you know this, then its easy to see that the distortion signature is actually what is important and not the class of operation.

Thanks for the additional information.  I always learn so much from these posts.