Testimony: Eurotubes

[BigShred]

I needed to retube my Mesa Road King so I happened across "Eurotubes" (http://www.eurotubes.com). Bob was extremely helpful and wrote me a loooong email about different tube configurations depending on style and sound desired.

I went with the following suggestion from Bob:

4x JJ 6L6GC (Matched Quad)
2x JJ E34L (Matched Pair)
3x JJ High Gain ECC83S
2x JJ Standard ECC83S
1x JJ Balanced ECC83S (for phase invertor)
2x JJ GZ34 (to replace the 2x 5U4)

Every email I sent received a response from Bob within a couple of hours max. The communication was phenomenal. My Road King had Mesa tubes in it and when I put these tubes in there I could not believe the difference I got out of my amp. There was a lot more clarity and "chunk". With the gain turned all the way up, the sound still retained all of that. The "flub" typical with Mesa Rectifier amps is gone.

From dealing with Bob at Eurotubes, I learned a lot about tubes in general and I am getting a sweet sound out of the Road King that you can not get from the factory.

One of the better experiences I've had buying gear on the net.

[microdmitry]

Except you shouldn't use anything but Mesa power tubes in Mesa amps, except if you have a bias meter and can measure idle current to make sure it's within acceptable limits.

That's because Mesas don't have a bias pot, so your tubes might be running too hot, which will shorten their lifespan and could eventually lead to a catastrophic tube failure, which, due to the fact that Mesas also don't have HT fuses could lead to output transformer failure. Which is very, very expensive.

[Paul Secondino]

In the case of Mesa amps , including the Road King, they are factory biased very very cold. There's almost zero chance of buying tubes that make it run too hot.


For example, with a normal medium output set of 6l6 in my Mesa mark 3, it was only pulling 19mA cathode current on my bias rite meter at about 440vP

After I had my tech install a trim pot for the bias, we set the bias at 38mA. This is almost twice as hot as the Mesa setting with the same tubes.And based on a power curve my tech put together of the amp,( which means he took readings of plate current,voltage,grid current, negative bias voltage ,etc, and made a chart to show the power curve at different volumes and bias settings) he determined that we could still run the amp hotter without going too hot.

On that note, Bob tests most all the amps that are out there to see what factory settings are before he puts together tube packages. So if your Mesa or most any other amp still has a factory bias setting, Bob will be selling you tubes that wont make your amp run too hot. But you should be checking the bias or having someone qualified do it for you jsut for the hell of it

[microdmitry]

There is, however, a chance. And that output tranny is at least $300 to replace, not including shipping back and forth.

And your new tubes could be set even colder, depending on their transconductance.

[Lefty Robb]

JJ's are the tits...

Thanks for the website, I just dropped him a note, I got 13 tubes to replace

[bammbamm]

Originally Posted by microdmitry

There is, however, a chance. And that output tranny is at least $300 to replace, not including shipping back and forth.

And your new tubes could be set even colder, depending on their transconductance.

There is a chance you'll get tubes that are bad out of the box and shorted plate to grid and burn up your wiring in the amp, I've had that happen before.

Odds are slim on either of these scenarios occurring.

Bob measures and matches all the tubes and gives you a solid recommendation on the best set for what you're looking to get out of your amp.

+1 for Eurotubes!

[microdmitry]

Odds are NOT slim of tubes from a different manufacturer having a drastically different transconductance! I don't know about 6L6's, but I've seen EL34's that, when substituted for another pair of EL34's would draw TWICE the current with the same bias voltage. This means the following in a non-adjustable bias amp:

1. If original tubes are biased properly and new ones are naturally "hotter" - they will be biased way outside of their acceptable range and when cranked they will glow red and eventually fail.
2. If the original tubes are biased cold, and the new ones are naturally "colder", the amp will be biased too cold which will lead to unpleasant crossover distortion in the power section.

Not putting in a bias pot is Mesa's way of getting you to buy their tubes over the lifetime of the amp. That's why some folks put in a bias mod.

[elcid]

Bob is the guy. He's been very helpfull with my Orange and my Princeton.

[Nordhauser]

Originally Posted by elcid

Bob is the guy. He's been very helpfull with my Orange and my Princeton.

Hes a very knowledgeable guy. He's definitely got my vote for JJ's in my Boogie Mark III.

[markyperfection]

i've traded emails with Bob for at least 5 separate transactions for gobs of different amps and his advice has always been aces. i think there is a certain degree of "mad-scientist" voodoo that a good amp tech needs to have and if this isn't a mad scientist:

then i don't know what is.

Bob is the king snake.

[bammbamm]

Originally Posted by microdmitry

Odds are NOT slim of tubes from a different manufacturer having a drastically different transconductance! I don't know about 6L6's, but I've seen EL34's that, when substituted for another pair of EL34's would draw TWICE the current with the same bias voltage. This means the following in a non-adjustable bias amp:

1. If original tubes are biased properly and new ones are naturally "hotter" - they will be biased way outside of their acceptable range and when cranked they will glow red and eventually fail.
2. If the original tubes are biased cold, and the new ones are naturally "colder", the amp will be biased too cold which will lead to unpleasant crossover distortion in the power section.

Not putting in a bias pot is Mesa's way of getting you to buy their tubes over the lifetime of the amp. That's why some folks put in a bias mod.

Wonderful, but when Bob of Eurotubes gives you tubes that he's checked as thoroughly as Mesa, I think the odds diminish.

[kotornut]

Originally Posted by microdmitry

Odds are NOT slim of tubes from a different manufacturer having a drastically different transconductance! I don't know about 6L6's, but I've seen EL34's that, when substituted for another pair of EL34's would draw TWICE the current with the same bias voltage. This means the following in a non-adjustable bias amp:

1. If original tubes are biased properly and new ones are naturally "hotter" - they will be biased way outside of their acceptable range and when cranked they will glow red and eventually fail.
2. If the original tubes are biased cold, and the new ones are naturally "colder", the amp will be biased too cold which will lead to unpleasant crossover distortion in the power section.

Not putting in a bias pot is Mesa's way of getting you to buy their tubes over the lifetime of the amp. That's why some folks put in a bias mod.

When I bought my Mesa from the Mesa store in Hollywood. They told me that I didn't need to bias any tubes as long as they are either 5881 (6L6) or (EL34) tubes, it was a Rectifier. I asked them, "does brand matter," they said "no." Just the type of tube itself. I figure they'd know because that is a store just for Mesa and is owned by the factory, and the salesmen are Mesa employees.

Now just to add the whole info, that was about 10 years ago now, so things could have changed.

[microdmitry]

Whatever. It's your amp, not mine.

[losgatosrg350dx]

tube depot is awesome alaso!

[kotornut]

Originally Posted by microdmitry

Whatever. It's your amp, not mine.

Don't own it anymore, but I never had any problems in 8 years. Not even a blown fuse. So there you are.

That being said, there is nothing wrong with mesa tubes. If the amp sounded great wehn you bought it, why would you need to change it?