tubes, glorious tubes

All I can say is that I replaced the EL84s in my Marshall DSL401 with JJs and it made a dramatic difference IMHO. The amp had much more clean headroom. I was reluctant to use this amp at a gig because it broke up at such low volume, but after putting the JJs in I could get plenty of clean tone at very high volume. Really made this amp sound much better. And I have read a few reviews where people substituted the JJs in the Epi. Most said they were very happy with these tubes.

These tubes do make a difference. I substituted a EL84 labeled "Mesa" in my Epi and did not like it at all. I have not tried the JJs in my Epi.

That leads me to believe that I need new power amp tubes. Is this a correct assumption?

That's almost correct. The VS only has 1 EL84 (power tube). I second Wes's recommendation for JJs. Tubes are relatively cheap so having a set of spares is always a good idea.

Playing at high volumes or low volumes makes mighty little difference in the life of a Class A tube. It's true that they run a little cooler when played hard, as the output power is taken from what otherwise would be waste heat on the plate. Practically speaking, they're about as hot one way as the other. EL84s dissipate a lot of heat for a tube with a relatively small envelope, so they run hot and tend to have shorter lives than big tubes run at lower temperatures.

just wondering, are epiphone amps any good? im considering getting one.

just wondering, are epiphone amps any good? im considering getting one.

Yes. If youre not looking for tons of features and just want an awesome tube amp the EVJ is just about the best bang for youre buck. All the Epi tube amps have proven themselves very good.

~Mike

One of the stock tubes on my Epiphone Valve Special is going, after about 3/4 of a year, playing it every day. The tone has gotten muddy and my volume cuts out and back every now and then. I've heard playing EL84's at low volume kills'em pretty quick, and that power tubes go twice as often as preamp tubes. That leads me to believe that I need new power amp tubes. Is this a correct assumption?

If so, I'm looking at either JJ/Tesla's or Ei Elite's. Anyone have 2 cents for me?

I just now finished doing a complete retube of my Peavey Duel 212 with JJ's from Eurotubes. Two words:

HOLY

MOLY! :shock: :shock: :shock: :D

The difference between the chinese tubes that were in there, and the JJ's is astounding. All the fartiness in the low end is gone, and I'm rediscovering why I fell in love with the amp in the first place!

I've gotta comment on Eurotubes' service also. I emailed Bob asking what he recommended for my amp, which has been out of production for about 10 years now. He was back within 2 hours with several recommendations, and a price quote.

But wait! There's MORE!

From the time I placed the order, to the time I had the tubes in, fired up and tested was less than 48 hours - and I used his standard shipping option! They were confimed as shipped two hours after the order was placed.

Now that's service!

I'd recommend both the JJ's and Eurotubes to you.

Is the Epi Valve Special a fixed bias amp? What would switching out the tubes entail? I've never swapped out, and really don't have the dough to go to a professional right now.

Hey Duffmaster,

The VJ is the easiest amp to do tube changes on! Just pull out the old ones, and plug in the new. The output tube in this amp uses cathode bias, so the proper biasing is "automatic". You only have 2 tubes, 1 - 12AX7, and 1 - EL-84. So you can replace both with JJs for under $20. If you are using stock tubes now, this will be the best twenty bucks you ever spend.

OOPS! I just realized this was a VS, not a VJ. It's pretty much the same except for the digital effects, and TWO 12AX7s. So that means a complete upgrade to JJ tubes will be $30.

Sounds good.

I wasn't sure on the biasing, thanks for that toobmasta.

The tubes are going to have to go on the christmas list, I've spent all my money on present for others, and I still need to work to get the dough for my brother and best friend.

Toobmasta didn't emphasize it, but he used the proper term, "cathode bias," which as he explained adjusts itself automatically for reasonable differences between tubes. If you see an amp with adjustable bias, it's going to be one with fixed bias. Sounds strange, but that's how it is. That's because fixed bias means a fixed bias voltage is applied to the power tube grids. That fixed bias is often made adjustable. (It doesn't have to be adjustable, and may truly be fixed.) Cathode bias isn't fixed, because the bias voltage depends on how much current is flowing through the tube. Some home or boutique amp builders and modders make cathode bias resistors adjustable. Makes for a confusing muddle of terminology! Just don't use "fixed bias" to refer to an amp that doesn't have adjustable bias.
:D

Fixed bias? I mostly avoid that term completely. Except maybe in the case of an amp that doesn't have adjustable grid bias. Fender Princeton for instance. I think the terms "self biased" or "cathode biased" are good terms to use for an amp like the VS or VJ.

Fixed bias is the proper term since the 1920s for a grid bias voltage supplied from a fixed source. (Originally a "C Battery," now usually derived from a voltage divider in the power supply.) Doesn't vary with the cathode current. Doesn't have anything to do with its adjustability or lack thereof.

"Adjustable" and "Non-adjustable" would be my suggestion for that distinction. Like I said earlier, all commercial guitar amps that I know of with adjustable bias are fixed bias circuits.
:D

Proper, shmopper, it's a term that's just about guaranteed to confuse the Average Joe. I won't use it that way, and you can't make me! :twisted:

Then you'll just create confusion. Making up a new meaning for a term that's been in standard usage for 80 years isn't a good thing. This is analogous to the discussion going on in the Music Theory forum about guitarists inventing terms like "Sus2 chord" that aren't recognized by other musicians. It looks ignorant, and is. Just because tube electronic gear has passed its heyday and now has been rediscovered by niche groups of users unacquainted with the long established canon of literature on this very mature, 100 year old technology doesn't mean that we should ignore it and try to reinvent the wheel. Anyone picking up a tube era electronic textbook or even a tube manual will quickly discover that "fixed bias" doesn't mean bias that isn't adjustable. Somebody using the term that way will just sound like someone who doesn't know much about tube circuits to others who are familiar with them. Somebody might be rather experienced and good at working on cars, but if he calls a carburetor "that gas mixer thing," he's not going to impress other mechanics as knowing what he's about.
:wink: