Can you use tubes for a 15w amp in a 50w amp?

Guitar Toad

Guitar Toad

Toadily Stratologist
Are amps rated for current draw?
Can you use the same tubes from a EL84 15w Blues Junior in a 50w Marshall head? This where you just call the guy at your tube source and let him select the correct tubes for you.
 
Re: Can you use tubes for a 15w amp in a 50w amp?

you can only use EL84s in a Marshall if it
A. Was made to run them.
or
B. You get yourself a pair or quartet of "yellowjackets" which plug into the tube socket, and bias a 6L6 or EL34 socket to run EL84 tubes.
 
Re: Can you use tubes for a 15w amp in a 50w amp?

The preamp tubes are the same, the power tubes are all together different.

el84 and el34 aren't interchangable without using Yellowjacket tube socket adapters.
 
Re: Can you use tubes for a 15w amp in a 50w amp?

:blackeye:
OK scratch the Marshall amp. I picked the wrong examples amps. I think I should have used Soldano for my example...or any 50w amp that also uses EL84 tubes.

For that matter it doesn't matter to me if the 15w and 50w amps have EL34's or EL84's or 6L6 tubes. The point of my question is can the 15w and 50w amps use the exact same tubes?
 
Re: Can you use tubes for a 15w amp in a 50w amp?

Only if it's designed to do so, or you use the YJs. An EL84 tube simply won't fit into the socket for a 6L6 or EL34. And you're gonna have to search a bit to find a 50 watt amp running EL84s...Peavey classics come to mind. I'm sure there are others, but you can't just swap tubes willy-nilly.
 
Re: Can you use tubes for a 15w amp in a 50w amp?

Lets refine the query a bit further. I'm assuming for the sake of argument that said 15w amp and said 30w, 50w or 75w or 100w amps all use the same tube format. Let's assume that they all use 6L6 tubes. Could you use the same tubes whether the amp is a 15w or 100w. I'm thinking this is where amp biasing comes into the argument.
 
Re: Can you use tubes for a 15w amp in a 50w amp?

a pair of 6l6 tubes in class ab push/pull will give you around 50w
a quad of 6l6 tubes in class ab push/pull will give you around 100w
a 6l6 tube in single ended class a will give you around 8w
a pair of 6l6 tubes in parallel singled ened class a will give you around 15w
a pair of 6l6 tubes in class a push/pull might give you 30w

you could use the same 6l6 for all these configurations
 
Re: Can you use tubes for a 15w amp in a 50w amp?

But keep in mind all those different amp designs sound different - they won't simply give you the same "6L6 Tone" and differing volume levels.

For example, if you want the sound of a 100-watt class AB push/pull 6L6 amp at small club volumes, an amp with 2 6V6's running class AB push/pull (20 watts or so) might give you a better approximation that 6L6's in single ended parallel class A. Maybe.

Understand?
 
Re: Can you use tubes for a 15w amp in a 50w amp?

Rich_S said:
But keep in mind all those different amp designs sound different - they won't simply give you the same "6L6 Tone" and differing volume levels.

For example, if you want the sound of a 100-watt class AB push/pull 6L6 amp at small club volumes, an amp with 2 6V6's running class AB push/pull (20 watts or so) might give you a better approximation that 6L6's in single ended parallel class A. Maybe.

Understand?
Click to expand...

I think so. Looks like I need to study an amp design book.

If what you say is accurate, that further corroborates that I need a 6V6 amp. I need rich overdrive a la Jimi's Red House tone which can be attained for upstairs apartment club levels. :lmao:
 
Re: Can you use tubes for a 15w amp in a 50w amp?

sound like you need a tweed champ with a 10" or 12" speaker

something like this https://taweber.powweb.com/store/kits_50a.htm#5F1A

a little amp with a single 6v6 will only be about 4 or 5 watts which is prefect for at home jamming. at low volumes it will be clean, depending on the speaker it will probably be loud enough to piss your neighbors off, but probably not enough to call the cops
 
Re: Can you use tubes for a 15w amp in a 50w amp?

It's funny - when Marshall needed a small amp, they built the 18 Watter with EL84's. IMO, it does a pretty good job of doing "that Marshall thang", although it has some of that compressed EL84 sound, too.

People really in the know about about 18 Watters and other small MArshallish amps swear that the 6V6 captures plexi tone better - that using octal tubes is more important than the "EL" on the front. A lot of people who've built or played them swear that a "6V6 Plexi" (basically a Marshall JTM45 or Plexi circuit with a 2x6V6 output stage) is an absolutley awesome amp for the kind of stuff you're talking about. Might be too loud for home, though.
 
Re: Can you use tubes for a 15w amp in a 50w amp?

This wasn't really meant to be another suggest an amp thread. But, I do like the recommendations.

The take home message I'm getting is that "power" tubes don't really determine the output of an amp. The transformer's rating defines a tube amps output wattage.
 
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Re: Can you use tubes for a 15w amp in a 50w amp?

Actually, the design of the output stage determines its power output. The transformers then need to be big enough (and spec'd correctly) to achieve that design.
 
Re: Can you use tubes for a 15w amp in a 50w amp?

To add to what Rich said, tubes do play an important role in the output, you won't get 50W from a pair of EL84s or a pair of 6V6s.

Also, you can't just pop EL84s into EL34 sockets, to begin with, they won't fit. 6L6s, 6V6s, EL34s, 6CA7s, KT66s, Kt88s, etc... all do fit into the same sockets, but the 6L6 family and the EL34 family are not directly interchangeable, it depends on the design of the amp. And finally, you may get away with putting 6V6s into a 6L6 amp, but the voltage may be too high for them. To be safe, I wouldn't.
 
Re: Can you use tubes for a 15w amp in a 50w amp?

Hello Dev,
How about KT88s? are they completely interchangeble with EL34s?
 
Re: Can you use tubes for a 15w amp in a 50w amp?

Ok, so this is really informative. I hadn't realized it before. If we are talking about amps of greater than 30w then most likely we are talking about a 6L6 amp or an EL34 amp.

EL84, 6V6 tubes are for lower wattage amps, less than 30 amps.

6L6's are more flexible and depending on the output stage design can be in higher of lower wattage amps.
 
Re: Can you use tubes for a 15w amp in a 50w amp?

a good 6v6 tube might give you 12w each
an el84 might give you 8 or 10 if you really push it
a 6l6 might give you 25 or 30
a good el34 should be able to give you 30

those are about safe maximums. 6550 and kt88's can probably get more like 50w per tube in class ab push pull.

different classes of operation and voltages will give you different power outputs

your output transformer needs to be able to handle the output from the tubes without over heating so using a 25w transformer to handle a 50w amp isnt gonna be good for long.
 
Re: Can you use tubes for a 15w amp in a 50w amp?

Dr.Mavashi said:
Hello Dev,
How about KT88s? are they completely interchangeble with EL34s?
Click to expand...

Not totally, they are more in the 6550 family, which is kind of a heavy duty EL34, but biases a little different. It's a pretty easy change, but it does require a resistor change in the bias circuit, sorry, don't remember the exact values off the top of my head.

Guitar Toad said:
6L6's are more flexible and depending on the output stage design can be in higher of lower wattage amps.
Click to expand...

Not really, you can run EL34s at lower wattages too, the JCM900s had high power/low power switches that ran the 34s at lower plate voltages and Rivera has 3 power modes on some of their EL34 amps.
 
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