Issue with ARC Ref 110 amp

Thanks BIF I’m pretty sure it’s one of the driver tubes and I’ve resolved to change all tubes. Hopefully that’ll solve the issue.

The hiss could be a tube or the speaker.  At least the amp is not blowing fuses.  Switch the speaker cables to see if the hiss moves.  If it moves, the problem is likely the amp.  If the hiss does not move, it is likely the speaker.

If the hiss moves, and the focus is back to the amp, check and adjust as needed tube bias.  Hopefully, you can adjust bias within ARC spec, which I believe is 65mV per tube. 

If the Ref 110 only permits you to set the bias on one tube in a pair and the other tube is a slave, I believe spec for the slave ranges between 57mV to 73mV.  That said, I try to source power tubes that match within 2 or 3mV to each other.

Assuming you can bias the tubes, that tells me you probably did not fry a bias resister.  If you come up with one or more wacko bias reading, then you probably fried one or more bias resisters.  If you know how to SAFELY do electronic repairs, you can change the bias resisters yourself.  If not, take the amp to a tech.  This is a "low-tech" fix.  Call ARC for ARC sourced bias resisters. 

WARNING:  there is lethal high voltage lurking around the innards of the amp.  If you do not know what you are doing, find a tech to replace the bias resisters.

OK, ... assuming you have the bias situation under control, tell me, ... how many hours have you racked up on your tubes.  If you are using 6550s or KT-120s, the useful life is 2000 hours.  The 6H30 driver tubes have a 3500 to 4000 hour useful life.  Do not be cheap, always use fresh tubes.

Last point, staying with the tubes.  Assuming your problem is not the speaker, and biasing is ok, you may have simple tube hiss.  FYI:  regardless of the age, tubes can hiss.  I just bought a Ref 6SE with brand new tubes.  One or more 6H30 audio circuit tubes in the right channel made a high frequency hiss.  ARC replaced the whole bank and all was good.

So, go back to my original suggestion.  If you are sure the hiss is not coming from the speaker and bias is ok, and you have localized it to the right channel in the amp, switch the tubes from the right bank to the left bank. Start with the driver tubes first.  If the problem persists, switch the power tubes. 

My guess is that if you eliminated the speakers as the problem, and you can bias the power tubes, you have one more hissing tubes. 

It is always possible that another passive in the circuit is causing a problem, but IME, tubes are a likely culprit.

Good luck and I hope this helps.  

BIF
                        

Thanks guys. After replacing speaker cables and moving IC cables to a different preamp input, the fuse doesn’t blow anymore but I can hear a subtle, high-pitch hiss on the right twitter. It’s not there all the time but comes and goes and starts to appear after a while, I guess when the amp starts to heat. Any idea?

After the second time, I noticed that one of the speaker cables’ spades was broken 

This I think is your problem. Tube amps do not like to be run into an open circuit. If your spade broke and this opened the circuit that could do serious damage to your amp. Then again could be a red herring. You didn't mention the sound cutting out at all like it would do if the connection broke, and we don't know what you mean by "broke".  My guess would be that it cracked, but not enough to cut out completely just enough to make it sound bad and at the same time create an unstable load the amplifier couldn't handle, causing it to blow a fuse.

The Artesania thing is probably a misleading detail. Your amp has a lot of venting but the Artesania isn't anywhere near large enough to interfere with that, at least not the one I found on-line. 

It could also be that this is all coincidental, and it just happens that a tube decided to go bad at the same time as a spade broke and you are trying out a new tweak.

There are also resistors under the tubes and if you burned one of those out for any reason the amp won't run and will only blow fuses until those resistors are replaced.  

Obviously the amp should not blow fuses.  

Step 1:  Maybe the speakers are the problem.  Does the amp blow fuses if the speaker cables are disconnected from the amp's output taps?  Warning:  If you disconnect the speaker cables do NOT pass a signal to the amp.  Turn-on the mute button of your preamp.  You can damage tube amps with output trannies if there is no load on the outputs.

If the amp only blows fuses when hooked up to your speakers, maybe there is a short in the speakers. I assume you are using intact speaker cables.  

Step 2:  If speakers appear ok, did you check your tubes?  If the amp will not stay on, do you have a spare set of tubes, even old ones?  If yes, swap out the tubes for a spare set, at least the quad on the right side, to see if the problem persists.  Turn the bias down before turning the amp on.  

Step 3:  If the amp stays on do all tubes bias ok? If one or more tubes do not bias, the tube or tubes in question may have arc'ed and blown a bias resister. 

If all else fails, call ARC customer service and ask for Greg.  I hope this will not require a trip to the factory or ARC service center.     

Good luck.  The Ref 110 is a nice amp.  I am sure you will get your rig back up soon.

BIF