So this year i bought a Harley Benton 15W tube amp. Great amp for my purposes and needs.
This week however, it stopped working.
The light went on as usual, but i got a faint sound, starting high, fading out fast to nothing and then no sound anymore.
In stead of the steady sort of hum i got when the tubes were ready for action.
A quick search on the net resulted in me looking at the tubes, and seeing that 3 out of 5 werenāt lighting up. These three are the pre-amp tubes, it seems.
This has led me to two new things: ordering a new set of tubes (all five of them) and starting to look at how a tube amp really works.
However, questions arose shortly after. Such as, the amp has a 3-year warranty.
Shouldnāt i contact the seller (Thomann) and see what needs to be done to get this fixed? (which i just did, explaining that i already ordered a new set of tubes. (I might be jumping the gun here)).
Should i replace the tubes when they finally arrive and see if that helps? Or just send them back and send the amp back for repair under warranty?
Itās just that i like the amp really very much. It sounds great (to my ears) with the pedals iām using now, so i would like to have it fixed asap.
I have other amps around, but they donāt sound as good (again, to my ears) as this oneā¦
Hi,
That is ā¦well uh ā¦ a bummer
You did read the manual and let the amp do the required preheating first and didnāt drag it around with the amp while it was on, etc.? With normal use you should definitely make use of the warranty.
I think Thomann is a pleasant company when something goes wrong (and that often happens with me and arround me ), but the solutions are always great with great personel contact
Greetings
I would get Thomann to fix/replace it. If you start working on it yourself, even by replacing replaceable parts, you may well void the three year warranty. Then if anything more serious goes wrong in the future youāre stuck with a busted amp and a repair bill.
This kind of situation is exactly why warranties exist.
Yep.
No dragging around, it has a fixed place in my cave. Doesnāt move an inch.
Preheating you say? Thatās mandatory it seems. Before that, it wonāt produce any sound at all. I have to wait for it to get ready. But after thatā¦ oh boyā¦
Indeed, that was what i was thinking too when i wrote, i might be jumping the gun here.
In my email to Thomann, i explained the situation and am now awaiting their reply.
Iāll start by saying I know nothing about tube amps however I would question if thereās 3 pre-amp tubes and none of them light up, doesnāt that suggest a bigger problem? It could be that the tubes are fine but something in the circuit before them is not, or thereās an electrical gremlin that has caused all 3 to fail?
Like I say Iām not a tube amp expert so I might be very wrong
Thatās also a posibillity. Right now, with what i know about tube amps (next to nothing) this could be something.
I hope not, but weāll see i guess.
Yes, I would question the failure of 3 valves (sorry, Iām not American) at the same time, unless the unit has been through some physical trauma.
Contacting them is definitely the right approach. But I wouldnāt cancel the order for new valves yet as valves are considered āconsumableā items and are NOT covered by the warranty.
My amplifier VoxAc15 does it earlier than the 2 to 3 minutes mandatory warm-up time (I thought almost immediately ā¦ yes yes how do I know ), but they say that if you use it earlier the tubes die sooner ā¦
Aha.
Iām going to ask them if it would be possible to fit the new tubes in the amp,
Thatās another thing i recently discovered online, but do not know if itās really a huge difference.
Different tubes, produce different sounds. How that works, i donāt know yet. But itās something that raises my interest.
IMO itās not. Itās like the claims that the age of the op-amp chips used on overdrive pedals makes them sound different. That turned out to be rubbish.
I was encouraged to buy ārelativelyā expensive replacement valves (JJ) for my Bugera amp, being told the improvement was ālike lifting a veilā. I was pretty happy with the sound with the original valves in, but I thought I would give it a try.
Guess what: it sounded exactly the same.
Note that there are very few factories in the world that make thermionic valves. Most valves, traditionally, have come from the Xpo-pul factory in Russia and are rebranded (Mullard, Sovtek, Genalex - Gold Lion, Electro-Harmonix, Tung-Sol, etc.) but thereās also JJ Electronic in Solvakia, and a couple of manufacturers in China.
And thereās this:
I doubt they would and, certainly not within the warranty.
I would focus on the fact that the amplifier has failed under warranty, rather than on the valves.
Actually, having had some more coffee, Iāve thought about it some more, and realised itās entirely possible that a single valve failure could make the others go dark.
The thing that makes them glow is a heater element in each valve, and that is normally fed from a single circuit. Itās a bit like Xmas tree lights where if one bulb fails, the others go dark, if the heater on one of the valves has failed, it would almost certainly make the others stop working.
I would start by turning off the power and visually inspecting the valves. If one looks significantly different from the others then itās likely itās failed. Things to look for are discolouration, or a white-ish powder covering the inside of the glass.
If you are replacing the power valves then in most cases you should consider making sure they are biased correctly to get the best performance/longevity/sound from the tubes. Thatās really a job for an amp tech - whether thatās worth doing on a relatively inexpensive amp is a call you will need to make.
Having owned several Hifi Valve amps and two that failed I would offer this advice.
It is unusual for all 3 pre-amp valves to fail simultaneously, it may be that they have not failed and from what you describe a component in the valve heater circuit that fires them up has gone, or alternatively the design does not have a circuit protection and something has failed and all are now shot as well.
When the 5 new ones arrive I would resist putting them in the amp depending on the cause of failure they could also get damaged.
I think as it is under warranty the best advise is to return it to Thomann for investigation and repair.
That videoās great. So tubes donāt do anything for the sound, itās how the circuits are built that matters. Have to keep that in mind.
I knew about the few factories that produces tubes/valves. I heard about that on the JHS show.
Itās all the same then i guess, only the name on the tube gets to put a price on it.
(much like cars these daysā¦ Peugeot, Fiat, Ramā¦All the sameā¦ different pricing).
Iāve already gone and taken the tubes/valves out of the amp. Iāll have a closer look this evening.
But from what i could see already, there seems to be a loose end inside the tubes. At the bottom, where the wires come out of the housing, thereās a wire not connectingā¦ I donāt know if thatās by design, of something burned or other. Iād need new ones for comparison.
Yep, thatās what iām thinking too.
Iām going to have a closer look at them, replace them and wait for Thoman to respond.
Iām now thinking of keeping the replacements for when the time comes they need to be replaced.
Or would it be better to send them back?
This is what I was thinking as I read down the replies. Having multiple fail at once it is likely one failed and the filaments (heaters) were connected in series as Keith describes. This is pretty common in the tube circuits I have studied. Iād bet you have a single tube that failed and when you replace that one, youāll back up making noise.
In general, it is the gain of the tube that is different (as in the amount of voltage rise the tube can produce, not distortion as guitarists tend to use āgainā to mean). Depending on what part of the circuit the tube is used, you may notice that gain difference. If it were in a stage intended to produce some overdrive, youād hear it get crunchy at a different point. Frequency response is not likely to be a big difference since the tubeās general structure is not altered enough to influence change at audio frequencies. I do not think you will find a significant change with a tube advertised as āimproved soundā.
Paulās comment here is true for the gain of the tubes. Matched pairs are important if the tubes are used as a pair. Youāll need to see the circuit schematic and know what you are looking at to determine that.
A quick couple thoughts on tube care:
Donāt play with the tubes cold. You can eventually poison the cathode. Look that up if you want technical details.
Donāt leave the amp on for long periods of time (like over night, weeks on endā¦). This also can poison the cathode and as well as deteriorate the filaments early. You can think of the filaments a bit like incandescent light bulbs. They are intended to heat the tube so it works properly, but they can also fail.
It might be more cost effective to send them back as I expect Thomann will either replace the whole thing if it is less than a year old or because it is is more cost effective to do so, if they get it repaired then it should get new valves anyway.
), but they say that if you use it earlier the tubes die sooner ā¦