Experiencing speaker imbalance, while amp headphone output is fine. Any ideas?

might be room acoustics... is the room and speaker placement and reflective surfaces symmetrical?

or else it may be the amp... try swapping tubes in one channel to the other, one at a time, see if the imbalance shifts

tighten, redo all wiring/connections

Ask your partner if they been messing with you FIRST. I get out the pepper spray and wave it all around.

Unplug your headphones all the way.. 

Check all your controls

Check all your connection. That all takes 5 minutes. Unplug and then plug ALL the way back in.

New gear 101, check everything 10 times. Then again the next day 10 more times. LOL

Big laugh @ pepper spray. HA.

So, I have done the unplugging/replugging and checked all controls.

Now, just tried swapping channels. Sent the perceived hotter L output to the R speaker, and the R output to L speaker. As expected, now the R speaker is the louder one. It's a difference of 10db at my usual listening level. Crazy. 

Next thing to try, I guess, is musical chairs with the tubes. I'm bummed though as these are brand new tubes.

I'm bummed though as these are brand new tubes.

It sounds like you burned in the tubes and found a dud.

Not familiar with that particular ARC amp, if it is new from a dealer then you can get a warranty replacement tube from ARC, assuming it is a tube issue. If you discover it is a tube, call ARC they will send you out a new one. Maybe even a new full set.

It sounds like you burned in the tubes and found a dud.

Thanks. I hoped that ARC's factory burn-in test would have ID'd the bad apples before shipping, but I won't be too unhappy if the issue is as simple as a bad tube.

if it is new from a dealer then you can get a warranty replacement tube from ARC, assuming it is a tube issue. If you discover it is a tube, call ARC they will send you out a new one. Maybe even a new full set.

Yep, brand new. Thank you for this info. Will lug it to my dealer to suss out asap.

OP did you keep the old tubes? Usually 24-48 hours after they have been moved or shipped. That is usually the deal. So they get burned in and then they are shipped and placed in service. Usually after 48 hours they are ready for normal service. Shipping and moving is a valve killer..

Take a pencil and tap the tubes with the volume down.. You might be surprised.

R&R the new one with an old one UNTILL you  get the new valve. Or XChange the set.. 5 minutes I'm up and running with my amps. Mac, Cary, VTL, DIY

Regards

OP did you keep the old tubes? Usually 24-48 hours after they have been moved or shipped. That is usually the deal. So they get burned in and then they are shipped and placed in service. Usually after 48 hours they are ready for normal service. Shipping and moving is a valve killer..

Take a pencil and tap the tubes with the volume down.. You might be surprised.

R&R the new one with an old one UNTILL you  get the new valve. Or XChange the set..

Thanks. So, it's a brand spanking new amp with new tubes aside from my 3 weeks of use (and it sounded great for the first 2 - 2.5 weeks!). I just tried swapping pre-amp tubes with each other and now my L/R balance is WAY better. R now just slightly louder than L, whereas before this swap, L was FAR louder than R. It was a 10db difference at my usual listening level. 

you need to get Audio Research involved.

And, buy thee a simple tube tester you will have for the rest of your life.

https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2334524.m570.l1313&_nkw=tube+tester&_sacat=0&LH_TitleDesc=0&_odkw=accurate+tube+tester&_osacat=0

make sure it comes with instructions, list of settings for tube types.

Please call your ARC dealer.  I see so many threads here about new equipment where the OP never mentioned contacting the dealer. Why?  I would not contact the company first.  When a company sells through dealers, part of the margin is to field the customer service calls.  

even well tested tubes, shipped, handled, packed/unpacked, can sometimes suffer from a version of infant mortality

op - wish you good luck, arc should and will take care of you

Please call your ARC dealer.

Thanks. I did first thing this morning!

even well tested tubes, shipped, handled, packed/unpacked, can sometimes suffer from a version of infant mortality

You were right on the money. Turned out it was just a bad tube that lived only 3 weeks. Replaced today and all is well.

Thanks so much everyone for the replies and help!

Swap the speaker cables left to right. At the amp.

Tubes are a consumable.  If that doesn't set well with you, solid state was invented for guys like that.

I'm glad it worked out well for you.  It's very frustrating when equipment is not functioning properly, but when you're buying new from a dealer, part of what you are paying for is a warranty and insurance for your peace of mind that someone will be there to assist you when something goes wrong.  I recently had an issue with a new phono preamp. I emailed my dealer and within the hour I received a detailed email from the distributor that explained how to address the issue.  It would be nice if this could be done with used gear as well, but unfortunately it's much more unlikely.  

@gnarmite

glad you figured it out

did you take @oldhvymec ’s advice and get pepper spray too? he also keeps a fire extinguisher handy next to his listening chair too, as i understand it

great mechanics are always prepared... 😂👍

I'm glad it worked out well for you.  It's very frustrating when equipment is not functioning properly, but when you're buying new from a dealer, part of what you are paying for is a warranty and insurance for your peace of mind that someone will be there to assist you when something goes wrong

Thank you. Luckily I have a great dealer and he got me sorted asap.

did you take @oldhvymec ’s advice and get pepper spray too? he also keeps a fire extinguisher handy next to his listening chair too, as i understand it

Best advice on the whole thread, and maybe the cheapest!!

Well I keep a fire extinguisher for me, the wife gets the water. I like to get even every now and then when she is getting shocked pretty good, I just want to ADD a little extra so to speak.. I keep a board handy to, at least that's what I tell her..

I use to get her to lick her finger and thumb and hold the lawn mower spark plug wire. I told her a lawn mower wouldn't start if you didn't do that. 

She figure it out, now you know why I carry pepper spray in the house. It still slows her down enough for me to get to the next bottle of pepper spray, after a couple and a Thorazine dart she'll calm down. She is a feisty one since (sence) I tried to blowing her up looking in the oven I left on for 5 minutes.  I gave her a lighter to look with.. 

She was a looker, not bad once her hair grew back.. Well most of it did on one side.. :-)

She is a good sport when she's asleep. My dog like her.. So does the rabbit.