DOA tube from Audio Research


I just opened a matched quad set of 6550 tubes I bought last year from ARC and one of them is DOA. How can this have happened? I thought they were the most highly screened and tested tubes available. Has anyone else ever had this happen? I immediately called their support line and got the support guys voice mail saying he is on vacation. This is really frustrating. I've been waiting until I had some spare time to listen at length to the KT88s I put in last year before I switched over to the new 6550s. DAMN IT!!!

VPI Classic, Rotel DAC, ARC SP17, ARC VS60, Golden Ear Triton 2s, Nordost and Shunyata. A reasonably decent system that I rarely have time to listen to.
dfwlistener

Showing 1 response by lostbears


I have owned ARC tube amps for almost 30 years. ARC manuals are really not all that helpful. You just have to learn from experience as you go. Here are some Basic rules that I go by.

Turn the bias way down when installing new tubes. You don't want a tube running with a high bias while the amp arms up.

The amp needs to warm up before checking the bias. I usually let mine warm up for about 30 minutes. Or check after a listening session.

When checking the bias the amp should be idle with no music playing. Let it settle for a few minutes if you were playing music.

Tube can drift quite a lot, especially when the tubes are new. You need to check the bias often when tubes are new.

After the tube have settled in I still check my bias once a month or so.

If tubes run hot they will not last as long. Also they have a greater chance of arcing. Checking the bias is cheap insurance. I am not familiar with the compu-bias meter, I have always used a multi meter. It might not be a bad idea to double check the bias with a multi meter. Just to see how accurate the compu-bias meter readings are. Tube amps are far more work than solid-state but I think they are well worth the trouble.