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LB30 vs V4B -> 4xEL84 vs 4x 6L6GC

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Hello,

I have a likely stupid question.

The Ampeg V4B is much more powerful than a Little Bastard because 100w is more powerful then 30.. ok, I get it

But when I look at the specs, both use 4 tubes, EL84 for  the Little Bastard and 6L6GC for the V4B

is the différence of power linked to the tubes, because a 6L6GC is considerably more powerful than a EL84 ?

Luc

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Basically, yes. The 6L6 is capable of producing a more powerful signal than the EL84.

There's a lot of technical knowledge required for a better answer than I can give, but basically, a 6L6 is a higher spec valve than an EL84.

Possibly why the CTM100/300 uses KT88's.

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Ignore me, I'm waffling...

EL84s are small B9A base tubes as opposed to  6L6 being much physically larger octal base tubes. Bigger is louder in this instance...

Edited by Telebass

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Different valves have different voltage and current limits and are also limited in the power they can dissipate. The 6L6 is designed for high power amps and is a 30W valve The EL84 was the predominating valve in domestic audio with a 5W dissipation but can be pushed to 8W in certain circuits. To get more power you also need bigger power supplies and bigger output transformers etc etc. 

Heat dissipation is important and bigger valves can dissipate heat more quickly, the connecting pins need to be bigger to handle the extra current.

The biggest valve I've seen in audio amps is the KT88 each of these can give 50w in the right circuit. To make high powered valve amps it's normal to use multiple valve circuits to get the power you want.

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On 05/09/2019 at 11:59, Phil Starr said:

Different valves have different voltage and current limits and are also limited in the power they can dissipate. The 6L6 is designed for high power amps and is a 30W valve The EL84 was the predominating valve in domestic audio with a 5W dissipation but can be pushed to 8W in certain circuits. To get more power you also need bigger power supplies and bigger output transformers etc etc. 

Heat dissipation is important and bigger valves can dissipate heat more quickly, the connecting pins need to be bigger to handle the extra current.

The biggest valve I've seen in audio amps is the KT88 each of these can give 50w in the right circuit. To make high powered valve amps it's normal to use multiple valve circuits to get the power you want.

Hello,

 

This really makes sens, thanks for this explaination.....

By the way using  2 x ECC81 in preamp. and ECC82 as driver  tranform this raging little amp in a real gem

Luc

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1 hour ago, skidder652003 said:

out of interest what are the JJ6550?

JJ are a Slovak firm that make valves. Long time since I had anything to do with valves but I seem to remember the old British kit tended to favour EL34's and US amps tended towards 6550's but it's a long time since the 70's :)

 

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1 hour ago, Skybone said:

The 6550 is an 8 pin base power valve, similar (but not the same as) an EL34.

but they go in ampeg SVT's so I was asuming they were a bit moke pokey than EL34's? PS I have absoloutely no idea of that of which I speak!

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36 minutes ago, skidder652003 said:

but they go in ampeg SVT's so I was asuming they were a bit moke pokey than EL34's? PS I have absoloutely no idea of that of which I speak!

At this point it is time to check out the circuit topology, power transformers, output transformers and the valve specs (loadlines etc). As a massive simplification EL34 / 6L6 operate in the same ballpark and  6550 / KT88 similarly, but in a bigger ballpark.  6 EL34s in my Soundcity - adequate.  8 X 6550 in the Marshall VBA 400, adequate ++ (and far too heavy to move around).  Best valve amp I ever owned - Hiwatt 200, 4 x KT88 :)

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