EVH 5150 III Micro head

[cdntac]

I dunno if you can hear the rattle in this clip or not but take a look at this:

http://www.youtube.com/watch?v=9XQVukrU1JE

But again, the rattling doesn't bother me and it doesn't seem to be affecting tone at all. Its not that severe --- especially compared to microphonic vids I've watched on YouTube.

If I rap the tube while in the amp I can hear the rattle somewhat through the amp.

My wife can maybe pick me up a tube tomorrow --- assuming the music store in the city she is going to has one.

Or does she need to pick up a matched pair? This is a very small store --- I doubt they will have a matched pair if even a single JJ 6L6.

But if this thing needs to be biased just due to a simple tube replacement in a brand new amp....I'm not going to be happy. Especially if I have to put out $$ for two matched JJ 6L6 tubes and pay for someone to bias it (which there won't be anyone within about an hour drive from me that can do that).

Please tell me I'm getting concerned over nothing Howard. I really, really LOVE this amp but if I have to put out $$ for this...

[BudLite]

You will need a matched pair, also they will need to be biased, If you buy the tubes that are pre matched for this amp (as Howard metioned earlier in this thread) you will not need to re bias , as they will fall into the range tha amp is biased at from the factory. If you bought the amp new, you could call your dealer and request that they have fender send you a matched pair of power tubes under warranty.

[cdntac]

I read the part where he was discussing tubes but it wasn't clear (at least to me) if the matching pair would require a bias since he mentioned the overseas testing facilities (or lack thereof) for tubes and they instead just buy matching duets.

What are the potential problems, if any, using the amp with the tubes as is?

[BudLite]

I dont think theres a problem other than the noise or that the tube may not have a long life. I would say its ok to play, the tubes should be covered for a short time under warranty.

[cdntac]

From what I've researched, I'd agree with you. Yet I'm certainly no expert in regards to this topic.

But the fact that a tube is bad and having to potentially put out $$ for biasing (though hopefully not tubes --- if Howard has shown us anything it's that he and Fender are doing things exceptionally well in regards to customer service) is more annoying to me than the bad tube itself.

[Gnarlly]

Originally Posted by cdntac

From what I've researched, I'd agree with you. Yet I'm certainly no expert in regards to this topic.

But the fact that a tube is bad and having to potentially put out $$ for biasing (though hopefully not tubes --- if Howard has shown us anything it's that he and Fender are doing things exceptionally well in regards to customer service) is more annoying to me than the bad tube itself.

If you want to play through tube amps, then you're going to have to get used to tubes going bad and new tubes needing biasing. It's the price we all pay. The tubes should still be under warranty - 90 days. See below.
http://support.evhgear.com/warranty/...ranty_2007.pdf

[cdntac]

Howard: You should never have to apologize for not replying quickly on a message board --- ESPECIALLY after work hours.

I forgot to mention: The rattling is NOT coming from the speakers.

It is definitely the tube itself. When I put my finger on the tube (when it is rattling) the rattle will stop.

The rattle is similar to the rattling that can be heard through some combo amps sometimes (again, not through the speakers). And it's not heard at higher volumes.

There is a bit of a sound heard when shaking the tube. It's slight...but it's definitely not heard in the other tube.

I assume that the two power tubes are inter-changeable between the two sockets? Perhaps I'll switch them around. Maybe one will seat better than the other (yeah, I know, slim chance but hey, sometimes small stupid things can make a difference).

So even if I were to get a matched duet of JJ tubes from Fender....the amp still has to be biased, correct?

[Jasonbax]

Are there bias switches for each individual tube socket? I guess the bias switch is per match set... Can you take pics of the switches? Why weren't gain rated tubes used for ease of replacing without rebiasing?

[Blix]

Originally Posted by Jasonbax

Are there bias switches for each individual tube socket? I guess the bias switch is per match set... Can you take pics of the switches? Why weren't gain rated tubes used for ease of replacing without rebiasing?

Bias switches? What do you mean?


The facility making the 50watters doesn't have the gear to gain-rate tubes.

[Jasonbax]

Maybe I don't understand aren't they bought gain rated. So if you buy all the tubes at a certain gain rating its all the same bias? Aren't there knobs on the board For adjusting bias?

[ken374]

one reason i went with Boogie amps no bias needed! most learn how to do it, in the past i found a tech on craigs list near by to bias my amps

[ken374]

the 100 watt heads the tubes are rated say 25 so when you order tubes from fender you order the 25 and you wont need to bias. They should of done that on the 50 watter

[Blix]

Originally Posted by Jasonbax

Maybe I don't understand aren't they bought gain rated. So if you buy all the tubes at a certain gain rating its all the same bias? Aren't there knobs on the board For adjusting bias?

Howard can obviously answer this better, but they probably buy their tubes in bulk, maybe matched, but not gain-rated.
There's a pot inside for adjusting bias, the red one seen at the top in this photo.



By blix72 at 2012-03-14

Originally Posted by ken374

one reason i went with Boogie amps no bias needed! most learn how to do it, in the past i found a tech on craigs list near by to bias my amps

Boogie's needs biasing too, but if you stick with Mesa tubes you can avoid it.

Originally Posted by ken374

the 100 watt heads the tubes are rated say 25 so when you order tubes from fender you order the 25 and you wont need to bias. They should of done that on the 50 watter

At your first tube change you can bias the amp to a pair of gain rated tubes, and just keep using tubes rated the same.


As I do my own biasing I'd prefer the bias pot to be accessible from the outside, but not much I can do about that...

[ken374]

new boogie mini rectifiers el84's plug and play, few of there 6l6 amps have a bias switch you flip on to bias

[LPMojoGL]

Power tubes can go any time. Some last forever. Some become microphonic rather sooner than one would think is acceptable. It is generally accepted that most tubes being made today are not as hardy or musical as tubes made in the past, from like the 40's-60's. Thus the high prices for NOS. Tubes aren't needed for all sorts of electronics like they used to be, so are only being made by a few companies in places like Russia and China.

If your tube is indeed rattling at an audible level when the amp is cranked enough to be heard in a band, and the sound is coming through the speaker, I would have the power tubes replaced by EVH if inside the warranty. Even if you can only hear it when playing over the amp when playing at lower volumes, that can still be annoying. Maybe try sitting the amp on a towel or some foam to absorb vibrations from the speaker cab. Or, use it as an opportunity to upgrade tubes, keeping the stocks for backups.

All 6l6 amps that I am aware of should be re-biased after replacing the power tubes.
Except Mesas, but they use the same rating on their tubes, so they are supposed to be plug n play. Personally, I'd still wanna check the bias.

On most amps, you have to pull the chassis to check and set the bias. It was this way with the EVH 100, and I'm guessing the same with the 50 watter. Some amps have external bias points, which are wonderfully convenient.
Anyway, it was easy to check the bias on the EVH 100. Using a test meter, measure across the test points for a pair of tubes, using the little pot to adjust for the desired setting. I'm guessing the 50 watter to be the same, only measuring for a single tube instead of a pair, and adjusting the pot for that tube. Amp on, speaker cab hooked up, tubes warmed and amp in play, not standby.
A person should be very careful to not touch anything else besides the test points and the bias pots. Damage to the amp and death to the person can occur.

Hope this is helpful.