Rogue Audio. Reliability issues? Anyone?

It sounds like a bad tube took out some other stuff. It happens. Running tubes takes more work and money than solid state. You'll have to decide if it's worth it but $175, bad tube replacement, and shipping doesn't sound that bad to me. 

Check your plate voltage.  Is it autobias?  if not, confirm your bias current by calculating the plate dissipation with P=IV,

Jerry

The bias is drifting upward.

russ69,

So much attention went into matched tubes. How am I supposed to just replace one tube and throw out all that paid-for attention to detail? I guess maybe the answer is to pony up more money for ANOTHER matched quad. Feels like a very, very expensive endeavor that makes the tube game silly. Do you think finding a used KT-120 with low hours will fit the bill?

@nickrobotron "I have friends, two to be exact, inform me that Rogue is notorious for this crap and their amplifiers are money pits."

Do your friends have firsthand experience with Rogue amps to make this claim? If they do which amps and what were the problems. I had a Rogue Cronus integrated for a few years, zero trouble with it. Also, and maybe I've missed them , but I don't recall seeing threads here or elsewhere thrashing Rogue amplifier reliability. Feel free to correct me on that by posting some links.

@nickrobotron matched tubes is of greatly exaggerated value.  Especially if your amp has good bias control.  

Now you're having trouble with bias (is my guess).  This is why I greatly prefer manual bias control.  So don't even consider paying for a matched set until you get everything back under control. Your amp will sound fine.

Finally, if you are using new production tubes they will be very close to the same.  Unmatched NOS tubes that may have even been manufactured in different plants and diferent years can have much more variance.

Jerry

How am I supposed to just replace one tube and throw out all that paid-for attention to detail? I guess maybe the answer is to pony up more money for ANOTHER matched quad. Feels like a very, very expensive endeavor that makes the tube game silly. 

If the power tubes have a lot of hours on them and one tube fails, it's a good clue that the tubes may be near the end of their lifespan and it might be a good time to replace the set. If a single tube fails early on, a single replacement can be found that matches your existing set. Yes, tubes can be expensive. I don't want to replace my dozen six-pac tubes unless I have to. Even cheap tubes times 12 get very expensive.  The cost of running tube gear may not be within your budget, perhaps you should think about going back to solid state. Tubes are not suitable for everybody. 

It’s a very very easy fix. Just one cathode resistor and a new tube. 
amd YES Rogue overbiases their KT88 amps so user beware. 

Rogue amps use manual bias. 

My opinion, for what it's worth is that Rogue builds very reliable products of which I have owned numerous ones over the years.  Customer support when there is an occasional issue is EXCELLENT and fast.  Tube amps/preamps DO need some regular TLC - like checking the bias every 30 days or so to prevent issues like complete failure.  

Rouge builds great gear. Matched tubes are greatly overrated if the bias is used correctly or you amplifier has a reliable auto bias. I would fix it and quit wizzing away money on matched tubes. 

While admittedly a long time ago, I recommended Rogue to a friend. He bought a new amp. Within a short time a tube blew taking out some resisters. It was still under warranty, but they would not cover it. My friend argued with the founded. I think my friend ended up paying for it to be repaired. That is not a good way to get a good reputation. But lots of egg on my face. Rogue never gets my recommendation.

Another vote for Rogue's reliability. I've owned (and still do) two of their preamps RP-7 and RP9 as well as their power amp Stereo 100 for years and have zero issues with them.  Build and sound quality is excellent.  I did have the RP7 upgraded to the RP9, sent it to Rogue for the upgrade with ~2 week TAT.  Rogue is a quality company in my experience.

So a post above says they have manual bias.  turn the bias down by 10 mA and that should help a lot.  If it is a KT88 then maxx plate dissipation is 40 watts.  I'd run it at 30 watts and if having problems, I'd use  25 for a while.

You need to know your plate voltage.  It is pin 3.  Either measure it or find a reference for your amp (this is amplifier specific, not tube specific, don't use plate voltage max off the tube data sheet).  

Then calculate your bias:  25= Voltage x current so bias current  = 25/voltage. 

Jerry

The amp uses KT120s

Per the amp’s manual:

Using the bias tool, slowly turn the screw on the potentiometer that is adjacent
to the switch until the bias meter reads ~ 35 miliamps (mA). Turn the screw
clockwise to lower the bias and counterclockwise to raise the bias. Note that
there are two ends on the bias tool. Using the end with the recessed
screwdriver will greatly facilitate this operation.
9) Flip the switch back into the “run” position thus disengaging the tube from the
meter circuit.
10) Repeat the above steps for each of the tubes in both channels.
As it is a quick operation, the tube bias should be checked on a regular basis. Note
that the bias will change slightly on a day to day basis as the wall voltage
fluctuates. Constant biasing will wear out the bias potentiometers prematurely so
do not adjust the bias unless it is more than 4-5 mA from the correct setting.

The Op didn’t state how many approximate hours he has on the tubes, but unless they are all nearing end of "expected life" , there’s no reason to replace all since each is individually biased. That said, the bigger immediate issue for the Op based upon a google search is that new KT120’s appear to be out of stock at a number of vendors.

They might have got somewhat of a bad rep for their cathode-bias amps of 20+ years ago. That would be the 88 and M120 models. These amps threw out a whole lot more heat, which can cause problems.

Their current tube amp models are manually biased via trimpots & built-in meter, and these have proven quite reliable. With any tube amp, there’s no 100% perfect fail-safe for a sudden catastrophic tube short. I had this happen with an Electro Harmonix KT90 in my Rogue Apollo monoblocks, circa 2010. It dusted a metal oxide resistor and singed ~ 1cm of circuit board trace. Trace was still working but the solder mask got burned off so Rogue replaced the whole board under warranty. So yes, a bad tube can cause collateral damage that requires service. I switched to KT120 tubes after that incident, and they’ve been exceptionally reliable. Never had another problem in the next 12 years of Apollo ownership.

Tube amps with advanced auto-bias & protection circuitry might have a slightly lower risk, and P2P wired amps have no PCB board to damage. Never had the slightest issue with my VAC auto-bias tube amps so far, though I’m only 4 years in with these amps.

In your case, I would definitely send the Atlas in. Bit of a bummer, but better to get this sorted now. It's a great little amp, and Rogue customer support is fantastic.

Power tubes are matched for Gm and Ip.

Bias controls static Ip [plate current].

Gm is how much the tube responds to drive change.

Mismatched tubes have more 2nd harmonic, i.e. fat tube sound coloration.

I match drivers, triode halves and power tubes. The difference is clearly audible.

See ieLogical Valve Tester.

@nickrobotron Tube gear is pricy to own. I had a GL KT88 eat its cookies at about 1k hours. [It’s silly to run w/o hour meters.] So now I have GL KT88 spare quad, spare pair and spare.

Most tube gear is pretty simple and easily repairable with a bit of knowledge and a schematic. Of course, if you’re careless it can kill you. $175 seems cheap enough.

I have had an RP-1 for years.  At about 2 years had to replace stock tubes. Then about 5 years had to send it in and have the front control panel board replaced as volume control went wonky. Proly $300 total.  They turned it around promptly. 
 

sounds great and I expect more years of service.  Good value product in my opinion. 

PM me if you need someone to take a look that is reasonable.

There are several KT120's available on eBay. Not my first choice by far, but I had a dead KT120 in my Chronos Magnum when it arrived as new to me used. The previous owner never checked the bias...  So, I picked up a pair. They were Tung Sol and they sound great. 

For the record (is there a record?) I've owned both tube and SS gear for a long time and although there have surprisingly few issues with either one, I can easily say that tube gear has been more reliable by far, and to say otherwise is blasphemy...or something...or you're not me maybe...

@nickrobotron what was the bias reading the last time you checked, and how long ago was that? 

Hey, it's a tube amp. Output tubes wear out and get replaced. I run KT120s in my tube monoblocks, and the new pricing is high right now, and for the past two years. If you are not aware, Sovtek - New Sensor is in Saratov, Russia. There are bigger problems going on in the world right now, that's why... supply is short now.  None of my regular suppliers have them. Yes, some people selling them higher on eBay.

Unless you know the age and hours on them, start with buying a pair and recheck bias closely on the others, replace them too if necessary. Or, ask around and find a local tech, they can replace a bad resistor.  Worth fixing the amp, and better for resale working than broken if you decide to move it down the road. Good Luck.   

FWIW.. I have been running a Metis Magnum preamp have I bought as New Old stock a few years ago and have had zero issues. Magnificent sound and punches well above its weight. I had a kenrad tube from the early fifties go bad once and throw a ton of feedback through the speakers. The preamp as well as the speakers were no worse for wear after thank God.

I've never heard anything but great things about Rogue's service. I had a Cronus Magnum for a year with no issues.

owned a cronus mag 2 for 3 years, an RH5 preamp, RP7 preamp and Stereo 100 power amp.  the only issue i had was a slight delay in the startup of the 100, fixed quickly by the dealer tech.  

@wolf_garcia  I've had the same experience as you, the tube equipment is more reliable than the solid state equipment I've owned.

I stuck a set of 4 NOS matched GE 6SN7GTB tubes in my original version Schiit Freya preamp (note that it’s the model that keeps the tubes on when you switch to one of the two "passive modes" which I only do to hear if the tubes are working properly, a handy feature) and they’ve worked perfectly and haven’t required replacement for maybe 4 years or more. I have unused original box GE replacements for them that sound exactly the same that are waiting in the wings for their big moment, along with Sylvania "chrome domes," new Tung Sols, whatever the original Russian tubes are that the thing shipped with, a few Amperex, etc. Part of the reason is my Dennis Had Firebottle SEP power amp also uses a single 6SN7GTB so I’ve collected a pile of ’em, even though I now mostly use the brilliant Pass XA-25 amp (I do swap in the Had amp from time to time when I feel it needs to get off the shelf, and it always sounds fabulous). Also I have a couple of cool all tube guitar amps (one is tube rectified and single ended) and I pretty much don't even think about their tubes...they simply work.

I’ve had an Atlas for years- never a problem. A bad output tube can cause a resistor to blow in any tube amp. Ive had problems with Sovtek EL84’s in other amps.

Thanks everybody! This has been a good read.

To the point of affordability of tubes; It’s not about money exclusively. It’s the time they take. I mean, when I get this amp back and throw some tubes in it, is it just going to fail again and blow something else in the amp? And then it’s gone for another two weeks and $475 out on the shipping and repair bill, plus a tube.

If it’s a blind gamble (on a not so cheap part) whether or not it won’t screw something up in your amp, that’s getting into “stupid” territory. Am I misunderstanding the situation? A perfectly functioning amp can be damaged by tube failure? And tube failure is random and not so uncommon?

I’m new to this and I haven’t built a level of trust with tubes so far, but I absolutely love the sound. I guess if I get burned again, I’ll go back to Solid State and donate $500 to starving children every sixth months. That’s better than having holographic sound on and off throughout the year.

As I mentioned in an earlier post I had a Rogue Cronus Magnum a number of years back, never had an issue with it. Sold it only because I wasn’t a fan of the sound of KT 90 tubes , solid state sounding to my ears. I presently have 3 integrated tube amps: an Ayon Audio Spirit 2 originally in my main system now in my 2nd system, zero issues with that for more than 12 years or so; a Line Magnetic 518IA in my main system , zero issues for 7 years; a Finale Audio 7189 MK2 also in my main system, zero issues for 5 1/2 years. Aside from those I have a Modwright Audio Elysee tube DAC in my 2nd system (previously in my main system) , as well as, a Modwright Audio LS100 tube preamp in my main system (hooked to the Modwright SS power amp in my main system). Both of the Modwrights have been trouble free for going on 9 years. Point of all of this is tube equipment isn’t necessarily any more prone to problems than solid state gear. Knowing that the power tubes have less expected life than the preamp tubes or rectifier tubes I change them out when they are nearing that point. The 2 integrated amps that are manual bias I check the bias once a month, and if I find a tube or tubes falling out of bias repeatedly on the high side beyond an acceptable level I replace them. You didn’t note anywhere in your posts the age of the tubes, nor your bias routine and how that measures up to Rogue’s instructions so hard to know if you possibly contributed to your problem or not. That said, given your angst about tubes maybe take some time researching solid state amps that meets your SQ goals coupled with a good reputation of reliability and sit back and enjoy the music instead of fretting over whether or not a tube is going to send your amp repeatedly back to the manufacturer.

@nickrobotron Rogue customer support/service is solid. It’s worth sending it in. They will fix it and make sure it’s up to spec.

I have owned RP1, RP5 and ST100. Rogue products represent great value but as with all tube equipment there’s maintenance and occasional failures happen. 
 

I since switched to Pass Labs preamp and amp and I do not miss tubes at all.

@nickrobotron   Tube systems are for the hobbyists that like to be more involved with their music system. They are not for everybody. I like rolling tubes, checking bias, and keeping my systems running in top form. I have spare gear if one piece of equipment goes down. Perhaps a tube pre-amp and a solidstate amp would get you what you are looking for.

I’m not bent out of shape. Just trying to understand. It’s all good. The amp is with Rogue now and I have new tubes on the way. So we’ll see how this pans out. 
 

I have my solid state amps to hold me over in the meantime, so I’ll certainly live. There's just something really exciting about the tube sound that I’m not ready to give up. This thread helped me understand that I had a stretch of bad luck. 

@nickrobotron 

Great! I wish you a speedy and satisfactory resolution :)

I got my 1st tube component about 20 years ago, and in that time I've owned over 100 components - more than half of which had tubes. I understand your trepidation with tube gear, especially given this false start. But if anything, I think I've had more issues with the solid state components. Transistors are far less forgiving than tubes when it comes to high heat and high voltage. 

There are 4 fuses, one next to each trim pot.  Did the one with the bad tube blow?

I've had one KT88 fail in the past 40 years and it took out the surface mount autobias board.

I'm probably not the typical tube owner as I have an hour meter and test and reseat tubes every six months. [about 500 hours]

I must stress that there is more to keeping tube gear going that just bias. A failing tube can either pass too much or too little current. When bias is checked, you should note the existing value, the datetime and the adjustment in a log.

If one tube is going in a different direction than its compadres, it's probably time to take action.

As far as those that claim bias is the only thing that matters, BUNK! You might get away with it in a single ended amp, but push-pull requires equal current change for equal grid change. If otherwise, the waveform is distorted.

And for all you rollers, you can change the sound by accenting or negating mismatch in the driver circuitry with mismatch in the power tubes. SO MARK YOUR TUBES SO YOU CAN PUT THEM BACK IN THE SAME PLACE if you really like the sound!!!

If you have multiple power tube pairs per channel and if you can test your tubes for Gm, you can balance the pairs to improve distortion. AND the match info written on the box ain't necessarily the same as it will perform at different voltages and currents. AND almost certainly not after a thousand hours.

stereo5,

Yes, the fuse popped when the tube went.

I have happily owned various Rogue Audio products for over 10 years. I have always been pleased with the availability to speak with Nick and even Mark himself. And no issues with product reliability. Surprised to hear the issues you've expressed. Hopefully you can resolve your problems but realize as stated above that tube equipment is an investment in time and money. A labor of love is required but you need to determine if it's worth it to you. But don't be afraid to call back to Rogue. They've always been helpful as far as my experience has gone.

Gee, I just spent $200.00 one way to send my behemoth solid state amp across the country for repair. It may cost $1000.00 by the time I'm done. Can I replace a $10K MSRP amp for that? Nope! I suggest looking at accessories here or on that other audio mart and find a pair of matched tubes to fit our needs. Then you have a spare when the next one fails.

I had a rogue integrated and one of the boards inside was bad from the get-go. On the positive side, they got back to me promptly over the phone and sent me a board so I could replace it myself. Worked good after that.

box it up and send it to me for repair and upgrades.

Happy Listening.

What I will say in addition to really liking my first foray into tubes with a Cronus Magnum II, is that I experienced my first fried tube, I got someone on the phone the first try at Rogue, and they didn’t want to sell me a power tube until they walked me through how to make sure nothing else was damaged.  I think I was on the phone with them 2 or three times in an hour or so, and was confident replacing the fried tube would be the cure.  

Great people who will get further business from me.

@Robotron I think it’s just bad luck, I doubt you’ll have issues going forward, if there was a design issue w the amp it would be common knowledge by now. I hope things go smoothly after you get the amp back, the sound is worth it.

Regarding power tubes, as others have said, no need to match if you have some form of bias adjustment. I actually just went back to the stock KT88s that came w my Willsenton R8 to preserve the life of my Golden Lions now that they are so much more expensive, and I can’t really say I notice a difference. And one of my original tubes is different because it was a replacement they sent me after one of them arrived with noise issues, so I know for sure I don’t have a matched set. In fact the internals look slightly different then the other KT88s. Lol it’s stamped KT88 but for all I know it could be a 6550. Sounds great though and it’s been about two weeks since the swap.

Well here is an option,

Pull the cover and look for any obvious burned resistors.

Find one replace it. Chances are thats all it is.

I had a M120 pair like an idiot-- I put in a tube without a Centering pin

Roasted 3 resistors,

I called rogue service told them Didn't feel like shipping it across the country, Serviced said look for any obvious burnt parts, I found 2 resistors replaced them and works fine. Took 10 minutes. Maybe not an option.

Alos might be time to look at a Class D replacement.

Good luck. Rogue has Great service. Have had 6 amps of theirs.

Running Apollos now.

Regarding power tubes, as others have said, no need to match if you have some form of bias adjustment.

Measured power and distortion?

Checked for HF oscillation?

I've owned my 99 Super Magnum pre for

25 years. It's not had so much as a hiccup.

My Atlas Magnum blew a rectifier once,

but that was my fault: I fumble-fingered

The power button.