Pathos Heritage

I just got my Pathos Heritage for my home in the USA, but I am experiencing something I have never seen before; when I first plugged it in with the volume at half it sounded pretty low, kind of scary low for a 80Wpc amp running Avantgrade Duo Mezzo XD speakers or Tannoy Kensington.

After running it for about 100hrs the loudness dramatically increased.

I have owned and own quite a few amplifiers and never seen something like this before.

‘this is REW’s measurements at the first few hours

and here after about a hundred


Yes a for a day an a half.

after I turned it on for about 2 hours, then I started to play  before playing music.


I know when I had my Pathos InPol Remix it was a good 300 to 400 hours before it really came to life and opened up.

I hear you, I am more interested in understanding what electrically could have happened that the amp almost double SPL gain. I can't think of an electrical reason.... I understand that sound will open up and get a given signature with time but gain? It has never happened to me and I have  and had own quite a few amps.

That is well beyond what break in should be. This is a problem.

I have never seen behavior like this, but one thing comes to mind. Do the tubes all light up properly?

Also what happens when you shut it down?


Tube might be the problem. 

If you can not check the tube, use the new matched new tube to try .

Interesting. The Avantgarde presents an impedence of 16-18 ohms which would likely halve the wpc capability of a typical SS amplifier but the AG’s are also 105+db. The Tannoys are 8 ohm but 93 db. Hmmm. That would lead me to believe the volume implementation is just linear. On some gear it comes on strong like an arc I had that would run you out of the room at 20% and Ive had other gear that required 50-60% to achieve listenable volumes. I wouldnt worry about it too much, some manufacturers tune their volumes to give the impression that by using less volume turn that you have alot of power in reserve while others tune their volume for linearity and sound quality. I would bet Pathos falls into the latter camp.

@ghasley Those 2 readings I posted are for the exact same volume setting just at about 100 hours of run time, that is what I am curious. If it was at different volume then it would not be a problem. 

I am not too worried, more curious than anything else, because none of the amps I ever had, doubled the SPL at

the same volume setting after just a few hours of running.