Audio Research Tube AMP Reliability

I was given an ARC Dual 75 gold front by a friend who found it on the sidewalk here in San Francisco after an estate sale. One of the power tubes had popped, all the filter caps were dead, and the power supply section of the board was fried. I replaced the caps and burned components, but I really didn't want to replace the power tubes. They had been a matched quad of old US tubes, GEs I think. Anyway, I found a nearly-matching single tube on eBay and biased everything closely. It did take me a few near runaways to get it all right, but since then it's been running fine. The boards are a little fragile, with small easily-broken traces, but the component quality is good.

I agree with what's been previously said.

I've owned a Dual 50 f, a Dual 51, Dual 76, Classic 120's and a pair of VTM 200's. In addition, I've had an SP-3, LS-2, PH-3, and PH-5.

The pre-amps are rock solid. Never a problem in 30+ years.

The amps are much more linked with the condition and quality of the output tubes. If there are the beginnings of minor noise or crackles through the speakers, or if a unit begins to blow fuses, or an individual tube seems to run hotter than the others, time to look at the tubes. If these little warning signs are ignored, a blown tube will take out a resistor and make a bad smell, resulting in a dead amp that is easily repaired.

If you use high quality tubes that have been run in before installation, you should be fine. ARC equipment is very well designed and built.

[I am interested in ARC because the sound is great intimate and truly beautiful.I am an original owner of PH5, CD3mkII and LS26 and over two years I never had troubles. They all work beautifully
But the few malfunctions I experienced with the amps were different.
My newer VS115 at approx. 165 hours during the warm up period suffered a fairly catastrophic failure.
The V1 tube was glowing with a white colour, a capacitor or perhaps a resistor became overheated and flamed out with blast and smoke.
Luckily the rest of the equipment were not damaged.
After two weeks the local ARC service repaired the unit and I had to pay for the tube.
At approx. 255 hours it happens again. This time I heard only a blast.I returned the unit to the local ARC and I am waiting but I am very disappointed.
(I checked the Bias and the wall voltage every time I heard music)
The same happened 2 years ago to my VS55 I previously owned at approx. 400 hours. At that case ARC had sent me through the local dealer a new circuit board. ]

The biggest problem isn't the fault of ARC. They rate their 6550's life span to be approx 2-3000 hrs. That being said most people don't keep track of the time they put on their tubes. A few ARC amps have Hobbs Meters on them (elapsed time on the tubes)which makes it easy to determine when a new output tube set is needed. As with any high current high voltage tube amp arcing can happen across a circuit board trace but this is usually not the norm. Most of the time a plate and/or screen resistor will open and require replacement prior to installation of a new output tube set and rebiasing. Remember, once that amp is on and the tubes are drawing bias current the clock is ticking.

I had a VT200 with a tube arc, because I bought tubes from a seller other than ARC. It took out a resistor, but contrary to a previous poster, that repair is about $165. It is the shipping that is expensive on that amp.
Your friend's amp has obviously not been repaired at ARC if it has signs of previous issues. After ARC repairs an amp, there is NO sign that there was a problem. The board is clean, and the traces are redone as needed to make it like new. I would say your friend is going to an unreliable repair person. He should send it to ARC. I have also owned, besides the VT 200, a Vt100 mk2 and a mk3, and currently have a Ref 110. Preamps have included SP9's and Ref2 and currently Ref3. The only problem I have ever had was from replacing tubes in my VT200 from a Canadian tube company. ARC is very particular about the tubes it sells. Live and learn.