Ref75 bias
 

I was sitting here, listening to my new ref5 and ref75, trying to get this break in process moving faster, when I had a thought. It was sounding pretty shrill and thin to me, which I just chalked up to breaking in. But I thought I should check the tube bias, since that is so easy to do. Well guess what...all four kt120's were way low on the bias voltage! I dialed them in, and most of the shrillness is gone, and bass has improved! At least it sure seems that way to me. Anyone have a similar experience with tube bias that was wrong from the factory? Is it just my houses power that might be a volt off or something?

Marc...When you get a new tube amp, you will experience bias drift often in the first month. So you should check it once a week and rebias if needed. Once it settles in, it will stay pretty constant. At that point, I would check it maybe once a quarter to make sure it is biased properly. Hope this helps.

Yes, thanks! This is my first tube amp. I don't know much about them, except that I'm starting to prefer their sound. The manual doesn't say much about this, but thankfully the ref75 makes it so easy a child could do it.

The Ref75 is also my first experience with a tube amp. Ease-of-use being able to set the bias with the front meters was a big selling point for me.

AC line voltage will effect the bias.

Don't adjust the bias unless the amp has been on for at least an hour.

Since you're still breaking in your REF 75, I recommend giving it a couple of cycles with Track 7 on the Cardas/Ayre burn-in CD.

Ah, thanks! That must be it.

Like you I had to bias my Ref 75 on installation but it has been stable since (9 months). Great system you now have !

I too had some shrillness to start with; most of it was gone after 50 hours. But came back around 120 hours for 20 to 30 hours. I checked the bias the first week are so, but I did not have to adjust it. I forgot about it until Tom showed up to install my Linn turntable and complete to setup of the speakers. He noted that the amp bias needed to be adjusted (it was at the low end of ok range). That adjustment was made around 300 hours. I checked the bias once a week and have seen little change. As with most things; give it a little time…it's worth the wait….Enjoy

Blaine

Also make sure there is no signal coming into the amp.

I'm around 50 hrs and it's getting better, but I think there is quite a bit to go. I'm enjoying the ride! Best sound I've heard in my home.