Upscale Audio -- Tubes and Reliability


Just wanted to get this out there for the benefit of A'gon members who own tube gear. All of my gear is ARC tube equipment.

I've been buying tubes from Kevin Deal - Upscale Audio for quite some time. Most recently, I bought a tube set for my amp. One of the KT-120 tubes didn't bias well. Kevin replaced the tube -- no questions asked!

In another case, the common carrier screwed up the delivery of a tube order. I left a VM for Kevin. He returned the call within 24 hours and made the situation right.

As an fyi, Upscale Audio burns in their tubes for 72 hours before testing and matching. Yes, there have been some glitches here and there, but so far Kevin has always come througth and made good.

Although I still buy some tubes from ARC, on rare occassion a few tubes blew shortly after purchase. Yes . . . ARC was 100% reliable in making good. Problem is ARC charges twice the price Upscale Audio charges.

Although I suppose one could argue that an advantage of buying from ARC is that if a tube goes bad and takes out some passives, ARC will pick up the tab. That may be true, but what good is that guarantee if you have to pack up your equipment and send it back to the factory.

In my case, I am fortunate because an ARC authorized tech lives near my house and makes house calls. True! As I reported before, one time a power tube blew and took out a bias resister. The tech came to my house and replaced the resister in about 45 minutes.

So for me, I guess the bottom line is this: if an UA tube goes bad and takes out some passives, is it worth the price savings to have the tech come out to fix the affected gear. So far, the price savings has justified the risk.

FWIW.
bifwynne

Showing 5 responses by hifigeek1

The reason ARC doesn't want those tubes in that series of amp is because that tube is mounted horizontally. Output tube sockets can become loose over time. It's less of an issue when the tube is mounted vertically. Because the KT-120 is taller, and heavier then it's 6550 brethren, it is far more prone to sagging in it's socket and losing contact with the socket. Thereby causing it to arc, damaging both the tube and surrounding circuit components.
Bifwynne. Well obviously being someone who services ARC under warranty I'm a bit biased. Did I just say that? There are quite a few ARC amps that I don't recommend people re-tube and bias unless the bias voltage points are outside the amp away from high voltage traces. These amps run at around 400Vdc and pack quite a wallop as Steve found out! Imagine someone with a weak heart or an unsteady hand, or improper test probes attempting to set bias. All it takes is one slip, and a trace can blow right off the circuit board and leave a crater in the board just for starters. Is paying for a few hours of labor worth that kind of dangerous exposure? I leave it to each person to answer that.
In addition, the front end tubes (6922) should be replaced every other time the output tubes are replaced. Set up after new tubes are installed is a royal pain and the tubes MUST come from ARC in order to set the front end up properly for lowest distortion. I don't set up the front end of Mk1's and MK2's unless I get the tubes from ARC. Mk3's use a different circuit topology.